REESE LIBRARY UNIVERSITY OF CALIFORNIA HAND BOOK OF PUBLIC HEALTH LABORATORY WORK AND FOOD INSPECTION. HY O. W. ANDREWS. M.I'... B.S..DUNELM; M.R.C.S., ENG.; D.P.H., CAMH. ; STAFF-SURGEON, R.N., LATE ASSISTANT INSTRUCTOR TO SURGEONS ON ENTRY, ROYAL NAVY. FELLOW OF THE ROYAL INSTITUTE OF PUBLIC HEALTH. TLondon : BA.ILLIERE, TINDALL & ("OX, 20 & 21, KING WILLIAM ST., STRAND. Portsmouth : CHARPENTIER & Co., 46, HIGH STREET. 1901. (All Mights Reserved.} CHARPENTIER . z -: 2 < j I 1 1 NAME OF FISH. a ^7 ! | I >> -~ -? >. 3 I 43 1 a > O II Barbel Bass Bream c e Lobster Mackerel ... Mullet (red) ... C e (' e e c e c e c e e e c c c e e e e C C c ... ,, (sea) ... Brill Carp Cattish Char Chub Coal Fish or Saithe Cockle Cod Conger Crab Crayfish (a) ... Dab e e c 8 C e e e e e c e s e c c s f 8 e 8 e c c c c e c e e e e (grey) Mussel Oyster (6) ... Perch Periwinkle ... Pike Pilchard Plaice Pollack Prawn Salmon & Sea Trout (c) ... Shad c e e e e e e e < ' s c 8 e c c c c c c e c e e e e e e e e e c p. c c c 'e e e c < (a) This is for sea crayfish. River crayfish can be obtained in the spring, summer, and autumn. It is a moot point whether it is legal to take fresh-wfcter crayfish from March to June. (b) Foreign oysters can be sold in the close season, and are to be had almost all through the year, even though they have been laid down in English beds for storage. (c) In the close season salmon from Holland and also from certain British rivers where net fishing is permitted later in the year than usual, are largely sold. (d) For the first six months the bulk of our London supply of shrimps comes from Holland, but Dutch shrimps are far inferior to the English, which are plentiful from July to December. The symptoms of fish poisoning are those of acute gastro- intestinal irritation as evidenced by vomiting and violent diarrhoea, or else prostration very intense in character and death by syncope or convulsions. In regard to poisonous fish, sailors have a very good rule, and that is, fish with scales are usually wholesome, those without are not. The livers of otherwise wholesome fish have been known to give rise, when eaten, to severe gastro-intestinal disturb- ance, as shown by vomiting and diarrhoea, followed shortly by a red-rash, and later on by desquamation. Mussels sometimes give rise to very severe symptoms, such as indigestion, nausea, and vomiting, diarrhoea, feeble pulse, and great prostration, numbness of the limbs, urticaria, and occasionally swelling of the tongue and fauces. It was recently found that non-poisonous mussels placed in the water of Wilhelmshaven soon became poisonous, and that if trans- 50 ferred to the open sea, soon became harmless again.* Further, it was found that after giving water from the harbour after filtration to the mussels they became harmless, and certain low forms of life were found in the water of the harbour which were not found in the non-poisonous mussels, nor in the water from the open sea. A chemical poison, called mytilotoxin, of the nature of an alkaloid and also very virulent bacilli, were found in the poisonous mussels. Mytilotoxin is said to act like curara in paralysing motor nerves, which is quite distinct from the poison which sets up gastritis and enteritis. Cases of Enteric fever have, in numerous well authenti- cated cases, been traced to mussels and oysters collected from w r ater contaminated by sewage, which had become infected by the bacillus of typhoid fever, where the only circum- stance common to the persons suffering from typhoid fever was the fact that they had partaken of the mol- luscs from an infected source. As a typical example we cannot do better than quote the outbreak of Typhoid fever at Wesleyan University, Middletown, Connecticut, U.S.A., given in the Appendix No. 3, to the report on "Oyster culture in relation to disease," by Drs. Bulstrode and Klein. The case at Wesleyan University was recorded by Dr. H. W. Conn. The students had some initiation suppers on I2th October; twenty-five cases of sickness, twenty-three of which were undoubtedly cases of typhoid fever followed as a result of these suppers, between 2oth October and gth November which agrees well with the supposed incubation period of from eight to twenty-eight days of these twenty-three cases thirteen were severe and four fatal. These students all ate oysters " on the half shell," i.e., uncooked, and this was the only circumstance in common. Other people attending these suppers had eaten oysters, but these were mostly cooked. On tracing the oysters to their source, it was found that they were all from Long Island Sound, and before reaching the retailer, they had been removed to the mouth of a fresh water stream for a few days to "fatten" ; between 250 and 300 feet above the place where they were left to " fatten " was the outlet of a private sewer which had been receiving the excreta of persons suffering from typhoid fever. Eels and Osphromenus olfax (Mauritian gourami) have been known to acquire poisonous properties by being kept in foul ditches or tanks. Many fish are unwholesome at the breeding season, and some French naval medical officers, who have had much experience in tropical waters, hold that many of the so-called poisonous fishes are only poisonous at that season. Many *24th Annual Report, Local Government Board, 1894-95. tropical fish owe their poisonous qualities to the fa6l that they feed on poisonous Medusae and corals. In mentioning fish, the flesh of which is either always or at times poisonous, no allusion has been purposely made to those fish which are provided with poison organs intended for defensive purposes. Fig. 15 GOURAMI (Osphromenus olfax.) Table of fish, certain species of which are known to possess poisonous properties (a) inherent ; (b) dependent on nature of food ; or (c) due to seasonal changes. Acanthopterygii or spiny -rayed fishes Including Spar- idce (Sea- Breams) ; Squamipinnes (Coral fishes) : Sphyraenidx (Barracudas); Scombridx (Mackerels); Carangidx (Horse-Mackerels); Acronuridse (Surgeons) ; and Atherinidoe. Pharyngognathi Including Labridse (Wrasses). Physastomi Including Siluridx (cat-fishes) ; Clupeidse (Herrings). Plectognathi\r\c\u&\r\g Sclerodermi, e.g., Batistes and Ostracion ; Gymnodontes (Dwdon, Triodon, Tetrodon). Fig. 16 Nasens unicornis. From the Indo-Pacific Ocean. 52 Naseus unicornis belongs to the family of Acronuridae or Sea-Surgeons, which are especially met with in the neigh- bourhood of coral-reefs, since they feed on the corals or vegetable matter found near the coral, they are liable to possess poisonous properties. Pig % 77 Heniochus macrolepidotus . Indian Ocean. Heniochus macrolepidotus is a highly coloured and beau- tiful member of the genus Squamipinnes or coral fishes, and is mentioned in order that it may be avoided. They are like other members of the family, carnivorous, feeding on small invertebrates met with in the vicinity of coral-reefs. The Pagelus erythrinus (Spanish bream), is a member of the genus Sparidx (sea-bream family), and off the shores of New Caledonia and New Hebrides the fish is rightly regarded 53 with suspicion, as at certain times there are numberless poisonous medusae off these coasts, from which they possibly acquire their poisonous properties. The Spanish navigator Quiros, who discovered the New Hebrides, nearly died after eating this fish, and in an account of Cook's Voyages allusion is made to symptoms of poisoning which followed the eating of this fish off the coast of Mallicolo (New Hebrides). Fig. 18 BREAM (Pagellus centrodontus). Lethrinus mambo also belongs to the family of Sparida? or sea-breams, and according to Pere Montrouzier (an authority on the natural history of New Caledonia), is very poisonous when full grown, but may be eaten with impunity when young. It is met with in the tropical parts of the Pacific. Mambo is the native name for this fish in the northern part of New Caledonia. Fig. 19 THE SNAPPER (Pagnis unicolor}. 54 The " Snapper," belonging to the Sparidae or family of Sea-Breams, is much prized in Australia and New Zealand on account of the excellency of its flesh. " It attains to a length of more than 3 feet and to a weight exceeding 20 pounds." (Flower). The illustration of Snapper, like that of the Bream, Herring, Cod, &c., is given in order to illustrate types of fish, and so afford help in identifying various species. Sphyraena barracuda, known in the service as " Barra- cudas," when met with in the West Indies are generally poisonous, through having fed on small poisonous fish. They are long fish, sometimes as long as eight feet, and forty Ibs. in weight. Extremely voracious, these fish are not necessarily poisonous, but only at certain seasons or when they have been feeding on poisonous material. Caranx fallax, or Horse mackerel, of which there are many species in the tropics, is wholesome when young, but poisonous when old. They are frequently met with in tropical Australian waters. Fig. 20 YELLOW-TAIL (Seriola lalandii). From S. Australia. The " Yellow Tails," which belong to the order Carangidse or. Horse-mackerels, of which an illustration is given in order to show the appearance of the horse-mackerel family, are much esteemed as food, and are met with in temperate and tropical seas ; they sometimes attain a length of from 4-5 feet. Tetragonurus belongs to a genus partly resembling the mackerels, partly the mullets. It is found in the Mediter- ranean, and is recognised by the body being rather elongated and covered with strongly keeled and striated scales. There are two projecting keels or ridges on each side of the caudal fin. It is from twelve to eighteen inches in length when full grown ; the flesh of Tetragonurus is generally believed to be poisonous. Scarus of various species, are beautifully coloured fish, some small, others weighing as much as fifty pounds ; they belong to the family Labridae or Wrasse, " Rock-fish," many 55 of which class are known by their thick lips, in certain cases internally folded so as to appear double. One variety of Wrasse, known as the Scarus cretensis, was much valued by the ancients for the exquisite flavour of its flesh, yet if it had Fig. 21 -WRASSE (Psendoscarns troschelii). From the Indian Ocean. certain food, produced diarrhoea. This fish was so much prized by the Romans that in the reign of Claudius, Elipentius Optatus, the Roman Admiral, sailed to Greece in order to obtain the fish and distribute them through the Italian seas. The tropical varieties of Scarus, known as parrot-fishes, on account of the brilliancy of their colours, are considered poisonous on account of the poisonous nature of their food, which are chiefly derived from coral. Fig. 22 WRASSE (Labrus maciilatus). The Siluridx, or cat-fishes, are for the most part fresh- water fish, met with in all temperate or tropical regions. They have smooth skins, devoid of scales. A few varieties of cat-fish enter the sea, and keep near the coast, and it is only 56 these which have the reputation of being unwholesome, the fresh-water varieties being good for food. Giinther in his work on fishes says, " frequently the poisonous fishes are found eatable if the head and intestines be removed immediately after capture." Giinther enumerates many tropical fish which are poisonous, amongst these are several belonging to the herring family, e.g., Clupea thryssa, Clupea loniceps, Clupea perforata, and Clupea venenosa. Clupea thryssa (sardine dore) is a common West Indian fish distinguished by having the last dorsal ray prolonged into a filament. Clupea thryssa is extremely poisonous, and people have been known to die quite suddenly with the fish in their mouths unswallowed. A species of Clupea which the French des- cribed as a poisonous sardine, occasioned the death of five men belonging to the French corvette Catinat, whilst they were lying at the anchorage of Balade (New Caledonia), in the year 1856. Clupea loniceps (the oil sardine of the Malabar coast), Clupea perforata (of the Straits of Malacca), and Clupea venenosa (of the Seychelles), are all known to have given rise to severe choleraic symptoms. Clupea humeralis, a West Indian herring, after feeding on Physalia has been known, Dr. Day says, to occasion death in a few minutes. Fig. 23 Tetrodon sceleratus. Tetrodon and Diodon, known as " Globe-fishes," have the power of inflating their bodies by filling with air their distensible oesophagus ; when the skin is thus stretched they roll over and float with their belly uppermost, and spines protruding : this has given rise to their being known as sea-porcupines, or sea-hedgehogs. The peculiar formation of the jaws of these fish, in which the bones of both jaws are confluent so as to form a beak with a sharp edge, should be noted. It was Tetrodon sceleratus which, according to Forster, poisoned some of Captain Cook's men whilst in the 57 New Hebrides. Letheby, quoting from Sir John Richardson, an account of a case of poisoning by a Tetrodon which occurred in Simon's Bay, Cape of Good Hope, in September, 1845, says, "the case was this: the boatswain's mate and purser's steward on board a Dutch man-of-war, after being Fig. 24 GLOBE-FISH (Diodon maailatus). From the Indian Ocean. warned of the poisonous nature of this fish, cooked and ate a piece of the liver directly after their twelve o'clock dinner. The boatswain's mate ten minutes later was so ill that he could not stand ; his face was flushed, his eyes glistened, his lips were swollen and rather blue, his forehead was covered with a cold perspiration. He was, however, quite conscious, and complained of pain and constriction of the throat, and he SHD Fig. 25 GLOBE-FISH (Diodon maculatus). From the Indian Ocean. Inflated. had a desire to vomit. In a few minutes he became para- lysed, his eyes were fixed, his breathing was laborious, his face was pale though his lips were livid, and in seventeen minutes he was dead." The other man died in twenty minutes with the same symptoms. The whole fish is said to have been only six or eight inches in length, and they could not have eaten more than half-an-ounce of liver between them. 58 Balistes or " file-fishes " belong to the family Sclerodermi (fishes with hard or granulated skins), both jaws are armed with eight strong incisor-like teeth, by which they are enabled to break off pieces of small corals upon which they feed; seaweed and molluscs are also favourite foods. The dorsal fin Fig. 26 FILE-FISH (Balistes vidna). From Indian Ocean. has three rays of which the first is very strong and roughened in front like a file (hence the name file-fish), it cannot be depressed unless the second spine has been previously depressed ; this second spine has been compared to a trigger which has given rise to the term trigger-fish. Ostracion or trunk-fish, universally recognised as poisonous, is remarkable for having the head and body armour-plated, by plates of bones, as it were, soldered together, the fins, tail, mouth, and a small slit-like opening, bordered with a skinny edge which serves as a gill- opening, are the only unprotected parts. All these movable parts pass through openings in the armoured coat. These fish are met with in Indian and American waters. Fig. 27 COFFER-FISH (Ostracion quadricornis). From the West Indies. Thynnus. Varieties of this fish are met with in tropical and sub-tropical seas; they are said by Giinther to be poisonous at times. The Bonito, or striped Tunny, (Thynnus pelamys) is a well-known variety, and an extract from Bennett's "Whaling Voyage," vol. II., page 278, quoted by Giinther, 59 says that " this fish is a very voracious and miscellaneous feeder," flying fish, calmars, and small shoal fish are their most natural food, though they do not refuse the animal offal from a ship. Amongst the other food found in their maw we have found small ostracions, file-fish, sucking fish, janthina shells, and pelagic crabs ; in one instance a small bonita, and in a second a dolphin eight inches long, and a paper-nautilus shell containing its sepia tenant." A variety of Zeus, Zeus Callus, or the Indian Dory, closely allied to the common " John Dory " is said to occa- sionally have poisonous effects when eaten. It is a native of the American and Indian seas. "John Dory," the English name for Zeus Faber, is said to be a corruption of the Gascon word J-au, meaning a cock, and Doree, gilt. John Dory shares with the haddock the honour of having been the fish out of the mouth of which St. Peter took the coin. The natives of New Caledonia are in the habit of treating cases of fish poisoning with the following remedy : a piece of a form of grass called "Job's tears" (Coix lachryma) is crushed against a stone in order to facilitate the flowing of the juice, then it is steeped in sea-water and chewed, the ex- pressed liquid is swallowed ; any value the remedy may possess is thought by some to be attributable to the sea- water, although the Coix lachryma undoubtedly possesses diuretic properties, just as are possessed by a decoction of couch grass. Fish are very liable to contain parasites in their flesh which are capable of becoming parasites of human subjects; but fortunately the process of cooking, if conducted thoroughly, suffices to render such flesh harmless ; parasites such as cysticerci and others infesting flesh perish invariably if ex- posed to a temperature of 50 C. (i22F.) for even five minutes. Bothriocephalus latus, belonging to the group called Cestoda or tape-worms, is the only parasitic worm which we know with certainty has been conveyed to man by fish. It attains to the length of twenty-four to twenty-seven feet, differs from T%nia solium and Tsenia me dio cane II at a in having an ovoid head ; it has two suckers or longitudinal grooves, and no booklets. The segments commence about three inches from the head, and number from 3,000 to 4,000. The segments nearest to the head are square, but those further removed from the head are broader than they are long. The eggs are oval in shape and open by a lid at one end. They are longer than those of Tsenia solium or Tsenia medio- canellata. From the ova, after immersion in water from four to eight weeks, embryos are developed, each possessing six hooks at the anterior extremity and a ciliated mantle ; these 6o embroys swim about in a rotatory manner in fresh water, for from four to six days, after which the ciliated mantle bursts and allows a six hooked non-ciliated embryo to be set free, then if swallowed by the pike or perch, or other fish which acts as an intermediary host, they bore their way into the muscles and become encysted. It is in the cysticercal form that they reach the human subject. Bothriocephalus latus is said to be Fig. 28 Bothriocephalus latus after Leuckart. About ten times natural size. Ovum magnified about 161 diameters. common in Russia, Sweden, Norway, Lapland, Finland, Poland, and in West Switzerland, especially on the shores of Lake Geneva. Eustrongylus gigas is the largest nematode worm known to infest the human subject, it is said to be transmitted from fish to man, but this is by no means certain. The male is 6i from ten inches to a foot in length, and a quarter-of-an inch in breadth. The female is said (Cobbold) to attain a length of over three feet and a transverse diameter of half-an-inch. The body is cylindrical, and more or less deeply tinged with redness. . Tinned Fish. The canteens on board men-of-war usually lay in supplies of dried fish and tinned fish, including herrings, bloaters, sardines, and salmon. Tinned fish should be consumed immediately after the tin has been opened, as degenerative changes, accompanied by the formation of poisonous ptomaines, are liable to occur, especially under the influence of heat. Anything remaining after the tin has been open for twelve hours should be destroyed. " It would appear," says Dr. Coppinger, R.N., " that such changes are more apt to occur in fish which have been preserved/r^A, than in those preserved by means of salt or oil.' 1 In one of his lectures the same author says, " several cases of poisoning occurred in H.M.S. Crocodile, a few years ago, from the use of tinned fresh herrings, which had been lying open for forty-eight hours in a hot climate before consumption. One of these cases proved rapidly fatal." Numerous cases of poisoning by tinned fish and other provisions have been recorded in the medical journals from time to time. The symptoms usually appear a few hours (between two and three hours) after the fish has been eaten, and consist of marked collapse, frequent vomiting, diarrhoea, with pea-green bilious stools, elevation of tempera- ture (103 to i04F), rapid small pulse, often delirium, restlessness, and intense prostration. If the patient does not succumb, recovery will probably in severe cases not be complete until after seven or eight days havs elapsed. The nature of ptomaines is indicated by the following, which have been isolated from putrefying fish Colloidine C 8 H X1 N ; Hydro-colloidine C 8 H N ; Neuridine C. H u N 2 ; Muscarine C. H N O 2 ; Gadinine C ? H l6 N O 2 ; Parvoline C 9 H X3 N ; The composition of these bodies is as stated by Dr. Luff in Dictionary of Medicine. APPENDIX. THE tuberculin test for tuberculosis depends upon the fa6l that when even the smallest tuberculous lesions are present in cattle, one is able to obtain the charac- teristic reaction with the injection of a dose of tuberculin of from 0-3 to 0-4 gram, i.e., 3 to 4 cc of i in 10 solution of tuberculin, prepared by dissolving i cc of crude tuberculin in 9 cc of 0-5 per cent, aqueous solution of phenol. This solution of dilute tuberculin must be used freshly prepared, as it will not keep well. The animal to be tested should be put to rest and the temperature in the rectum taken the day before, and again on the day of the injection. The solution of tuberculin is inje<5led (taking the ordinary aseptic pre- cautions) into the loose cellular tissue at the junction of the neck and shoulder. The temperature must be taken twelve hours after the injection, and twice again between the twelfth and twenty-fourth hour following the inoculation. Any animal which shows a rise of temperature amounting to- i'4C must be be considered tuberculous. An animal which shows a slight elevation of temperature amounting to between 0-5 and o'8C is considered healthy, but one which shows a rise of temperature amounting to between o - 8 and i'4C must be regarded as suspicious, and subjected to another injection after the lapse of one month. The method of preparing tuberculin at the Pasteur Institute, given by Besson* in his work on Bacteriology and Serotherapy, p. 443, is as follows <( A culture of avian tuberculosis is grown inglycerinated broth in a bacteriological flask. Avian tuberculosis is used in preference to the human- variety because it developes more rapidly. The culture must develope a thin veil-like pellicle ; this veil-like pellicle appears from the fifteenth to the twentieth day, when grown at 37C ; the culture is complete at the thirty-second to the thirty-fifth day. The whole of the culture is sterilized at iooC, then concentrated to one-tenth over a water bath ; the liquid thus obtained is filtered through paper, and con- stitutes the crude tuberculin (tuberculine brute). This tuberculin is a brownish liquid of sirupy consistence, possessing a slight odour of characteristic sweetness." Technique Microbiologique et Serotherapique par Le Dr. Albert Besson. Paris Bailliere et Fils, 1898. 64 Besson gives the detail for purifying crude tuberculin by precipitation and drying, but the methods of purification by precipitation are expensive, and entail a loss of nine-tenths of the tuberculin. Crude tuberculin injected into healthy animals produces no symptoms beyond a slight rise of temperature. A guinea pig can bear 2 cc without any inconvenience ; a rabbit can bear very well 5 cc, it shows only a slight amount of fever and a transitory loss of flesh, and quickly recovers ; Dogs and cattle do not re-act to 10 cc. Man is much more susceptible than even a guinea-pig, 0^25 cc producing in man severe indisposition temperature rises to IO2'2F (39C), there are shiverings, diarrhoea, and vomiting. Even *oi cc of tuberculin can produce in man a slight rise of temperature. Man is 1000 to 1500 times more susceptible to tuberculin than the guinea-pig. With tuberculous animals the inoculation of minute doses of tuberculin produces so intense a reaction, that it is liable to bring about a rapid death. Half a cc of properly prepared tuberculin is rapidly fatal to a guinea-pig inoculated five or six weeks previously with tuberculosis, 3 to 4 cc of dilute tuberculin is, as stated above, the dose for diagnostic purposes. Stronger doses are liable to cause death if the animal be tuberculous, whilst, as we have already said, a healthy bovine animal shows no reaction with 10 cc of the crude tuberculin, which is ten times stronger than the dilute. These facts should point to the extreme value of tuberculin as a means of diagnosing tuberculosis in cattle, and the extent to which it has already been applied in Denmark and other countries, is shown in the statistics given on page 26. INDEX. PAGE Accidents to Animals . . . . 19 Actinomycosis .. .. 27 Act, Merchant Shipping .. .. i$ ,, Stamping out .. .. 2 i Age of Cattle determined .. .. 10 Sheep ,, .. I0 Aitches . . . . . . 5 Anthrax . . . . 20 22 Arctic Expedition, Grinnell . . . . 16 Australian mutton .. .. ij Austria, tuberculosis . . . . 26 Avian tuberculosis . . . . 40 Badly-bled meat . . . . 9 Balistes vidua . . . . 58 Bang, Professor . . . . 2 6 Bavaria, tuberculosis . . 26 Bay salt . . . . . . ij Beef, prime . . . . 5 ,, refrigerated .. .. 14 Blood in trichinosis . . 35 Blown veal and lamb .. .. 14 Bone, amount of .. .. 12 Bonito . . . . . . 58 Bothriocephalus latus . . 59 Bovine tuberculosis .. ' ". , 23 Bream . . . . 53 Breathing . . . . 5 Breeding season and fish . . 50 Brisket .. .. .. 6 Bull-beef ... .. 23 Caranx . . . . 56 Carcass inspected as a whole . . 10 Catarrhal diseases . . . . 42 Cat-fish .. .. 55 Cattle plague . . . . 20 Coenurus cerebralis . . 38 39 Chicken cholera .. .. 41 Chip .. .. .. 42 Chuck .. .. 12 Clod .. .. .. 12 Clupea harengus . . . . 46 ,, loniceps .. .. 56 ,, perforata .. .. 56 ,, thryssa .. .. 56 venenosa .. .. 56 66 PAGE Cod ... .. .. 6 Cod-fish .. .. 48 Coffer-fish .. .. 58 Commissioners on Tuberculosis . . 24 25 Condition .. .. 6 Congress of Tuberculosis . . 25 Cooking, loss on . . . . 18 ,, varieties of . . 18 Decomposed Meat .. .. 19 Diodon maculatus . . . . 57 Dog-flesh .. .. 13 Draining, from meat . . 12 Dressing Cattle . . . . 9 Dropsy .. .. n Eczema epizootica . . . . 35 Eels, poisonous . . . . 50 England, tuberculosis . . . . 26 Enteritis, fowl . . . . 42 Eosinophilia . . . . 34 Errors of diet (chicken) . . 42 Eustrongylus gigas .. ... 60 Fat, excess of . . 12 ,, too yellow . . . . 12 Fish, classes of . . 45 File-fish .. .. .. 58 Flank .. .. 6 Fluke .. .. .. 36 Fore-rib . . . . 12 Foot and mouth disease .. .. 35 Foot-rot .. .. 35 Fowl scab . . . . 44 France and tuberculosis . . 25 Freibank .. .. 25. Freshness in fish . . . . 47 Frozen Meat . . . . 15 Gapes .. .. 42 43 Germany and tuberculosis . . . . 26 Gid .. .. 37 Globe-fish .. .. 56- Goat-flesh .. .. 13 Goggles .. .. .. 37 Gourami .. .. 51 Grapes or pearls . . , . . 1 1 Greasy fish . . . . 45 Greener's Humane Cattle Killer . . 7 Haddock .. .. 47 Heniochus macrolepidotus . . . . 52 Herring .. .. 45 Hertwig's experiment . . . . 35 Horse-flesh .. .. 13 ribs . . . . 14 ,, tongue .. .. 14 6 7 PAGE Ice, keeping fish on. . .. 48 Inspection of cattle before slaughter . . 19 Job's tears .. . . 59 Joint-ill .. .. .. 27 ' Kernels " . . 13 Labrus maculatus . . . . 52 Lamb, blown . . . . 1.4 Lethrinus mambo . . . . 53 Live animals, points of . . 5 Liver, Horses' .... ... 14 Lymphatic glands .. .... 13 Mackerel . . . . . . 45 Marrow, colour of .. .. 12 Meat, characters of good .. .. 12 ,, reaction of good .. 12 bad .. .. 12 Merchant Shipping Act . . 15 Middle-rib .. .. 12 " Mincers " . . 23 Milk-fever .. .. 39 Mussels . . . . 49 Mytilotoxin .. .. 50 Naseus unicornis . . . . 51 Nocard on tuberculosis .. .. 25 Offal, definition of term . . 9 Oysters and typhoid fever . . . . 50 Ostracion quadricornis . . 58 Pagellus erythrinus .. ..^ 52 Parasitic diseases, animals . . 29 ,, ,, chickens . . .. 42 Parasites of fish . . . . 57 " Pate-de-foie gras " .. .. 41 Partially decomposed meat . . 19 Parturient diseases . . 19 39 Pig-typhoid . . . . 28 Pip .. .. 42 Plaice . .. 47 Pleuro-pneumonia .. .. 21 Preserved meat .. .. 16 18 Prime beef . . . . 6 Protective inoculation . . 23 Provisions, salt . . . . 15 Prussia, tuberculosis . . 25 Poisoning, symptoms of fish . . . . 48 Poisons and meat . . . . 19 Pork, measly . . . 3 ,, salt .. .. 16 Pseudoscarus troschelii . . . . 55 Ptomaines . . . . 61 Rainey's capsules . . . 34 68 Reaction of meat . . . . i 2 Red-fleshed fish . . 45 Refrigerated beef and mutton . . 14 meat, stripping in .. 15 Refrigeration and Cysticerci . . . . 29 Rib .. .. 37 Richardson, Sir John . . 57 Rot .. .. .. 37 Salt meat, value of . . . . 16 Salting meat, process of . . 16 Sardine dore . . . . 56 Scarus .. .. .. 54 Scour .. .. 42 Season for fish . . . . 48 Sea-surgeons . . . 52 Setting of meat, conditions affecting . . 9 Sex, how determined .. n Sheep, age of . .' . . 7 pox .. .. 27 Shin .. .. .. I2 Siluridae . . . . 55 Slaughter, methods of . . 7 Snapper .. .. M Sphyraena . . . . 54 Stag .. .. n Staggers .. .. 37 Stamping out system .. 21 Stripping .. .. n Strongylus filaria . . . . 38 Sturdy . . . . 37 Taenia mediocanellata . . . . 30 Taenia solium . . . . 31 Teeth .. .. ..67 Tetragonurus . . . . 54 Tetrodon sceleratus . . 56 Thynnus . . . . 58 Tinned fish . . . . 61 Tongue of horse and ox .. .. 14 Trichinosis . . . . 33 Tuberculosis . . . . 23 Tunny, striped . . . . 58 Turn . . . . . . 42 Veal immature . . . . 14 Viscera . . . . 12 14 Wasters . . . . 23 Weight of cattle determined .. .. 6 White-fleshed fish . . . . 45 Wrasse . . . . . . 55 Yellow-tails . . . . 54 Zeus faber . . . . 59 Zeus gallus . . . . 59 PART II. WATER, AIR, MILK, FOOD-STUFFS, WINES, ETC. PART II CHAPTER IV. WATER EXAMINATION. In collecting a sample of water, care must be taken that the vessels employed are themselves irreproachable, the bottles should first be well rinsed with dilute hydrochloric acid, then with the purest water available, and finally rinsed and filled with the water to be examined. Not less' than a Winchester quart bottle should be taken for examination, and if a full analysis is required, two Winchester quarts should be taken ; the bottles must be closed with well-fitting glass stop- pers, and the stoppers capped with pieces of India-rubber cloth, parchment paper, or any similar material available, no luting of any kind such as linseed meal or sawdust should be employed. The bottles should be clearly labelled with the source and date of collection of the water, and a form stating the nature of the source of water, whether from a spring, well, etc., should accompany the sample, together with certain details, thus : if from a well, the depth, nature of strata through which it passes, and a concise account of the nature of the collecting surface, whether there is any protection against surface washings, whether there are any likely sources of con- tamination such as cesspools, defective drains, middens, etc. If from a water-supply such as is met with in towns, it should state whether the supply is constant or intermittent, whether the health of the people using the water has been good ; if there have been any cases of recent sickness, the nature of the illness to be stated. And lastly it should state what is the nature of the storage, if there be any, and what are the reasons for the analysis. On receiving a sample of water, if it be possible to make a bacteriological examination, this should be done at once, and the chemical examination of the water begun with as little delay as possible. The examination, apart from the bacteriological one, is divided into three parts : 68 (/.) Physical characters. (//.) Chemical examination. (#) Qualitative. () Quantitative. (///.) Microscopical examination of the sediment. /. PHYSICAL CHARACTERS. (/) Colour. In good water when a column of 18 inches is viewed from above on a white ground a certain colour is generally noticeable, this should be of a bluish grey or green- ish tint. If it is brown this will probably be due either to (a) iron, (b) peat, or (c) sewage. (a) If due to iron, the iron will be tasted, as little as 0-2 grain of iron per gallon can be distinctly tasted and the qualitative tests for iron will reveal its presence. (b) If due to peat the taste will be peculiar, there will be a peaty smell on warming, the reaction will probably be slightly acid, there will be a considerable amount of oxidisable matter, and a microscopic examination of the sediment will probably show peaty vegetable matter. (c) If due to sewage a disagreeable smell will be notice- able on warming, and the water will show evidence of animal organic contamination in the subsequent tests. (2) Clearness. This is best judged by seeing to what depth printed matter can be read distinctly. Turbidity may be noticeable, if this is due to finely divfded clay which is suspended this will not settle down for a long time, but if due to coarser impurities these will subside after about twenty- four hours or so, and the nature of the sediment can be determined by collecting it in one of the ways noted further on. (j) Lustre. This term describes the amount of aeration in the water, and may be described as Brilliant, Vitreous, or Dull, according to whether the water is well or badly aerated. (4) Taste. This should be agreeable and possess the indescribable quality known as palatibility ; as a rule this is due to aeration ; good waters are always palatable, but the converse by no means always holds good, since some of the pleasantest tasting waters have been known to deal death to all who drink thereof. A water has a saline taste when the total solids are present to the extent of about 100 parts per 100,000, or less if calcium sulphate be present to any extent. When the salts 69 are chiefly composed of sodium chloride, and present to the extent of 120 parts per 100,000, the water is distinctly brackish. Sodium chloride may be present to the extent of 75 grains per gallon (107 parts per j 00,000) before it can be distinctly tasted Iron is readily tasted when about 0-35 parts per 100,000 of ferric carbonate is present. Rain water is generally mawkish in taste, and distilled water free from dis- solved gases tastes flat. (5) Smell. Occasionally a water possesses a distinct odour, such as the Harrogate and Strathpeffer waters do (H ? S), but as a rule even in polluted waters no smell is noticeable until it has been warmed, this should be done by taking 200 cc of the water in a clean stoppered bottle, plunging it in a basin of water having a temperature of 6oC. (i40F.), and after a few minutes removing the stopper and smelling ; a good water should show no smell on being subjected to the test of warming. (6) Sediment. This is collected by shaking the sample and pouring some of it into a sediment glass, which should then be covered and set aside in a cool, dark cupboard; at the end of a few hours the sediment may be removed with a pipette and examined microscopically with a low power, (i inch or \ inch) objective. The nature of the sediment should be carefully noted ; this may be Mineral, Vegetable, or Animal. Mineral matter; Sand particles show rounded outlines and are unaffected by hydrochloric acid ; likewise clay and marl will be unaffected by this acid. If the sediment consists of iron it will be present as hydrated oxide Fe (O H) 6 , seen as reddish brown amorphous masses, soluble in hydrochloric acid and giving a blue colour with potassium ferrocyanide. Chalk particles dissolve with effervescence on the addition of a drop of the acid, and prior to this show, as a rule, a rounded outline. Vegetable matters include debris, such as pieces of wood, leaves, living or dead algae, desmids, diatoms, linen and cotton fibres, spiral vegetable cells, potato or other starch cells, macerated paper, &c. The last few items are par- ticularly important as they denote contamination by house refuse ; some of these will be described in detail later on, vide p. 102. Animal matters. Animalcules abound in water containing decaying animal or vegetable matter, and in water which has been allowed to stagnate ; although many of them are harm- less, yet they show that there must be food to support them. Some of them are readily visible with the unaided eye, such as Cyclops quadricornis (fig. 29), or Daphnia pulex, met with in 7 o pond water, many varieties are microscopic, and are always found in pond water or water allowed to stagnate and exposed to air, such as rainwater in casks; amongst these are the Protozoa which are sub-divided into (., the estimation of free or saline ammo- nia, it is not necessary to compare all three of the distillates with the standards, only the first of the series need be compared since j of all the NH 3 has been found by numerous experiments to come over in the first 50 cc distilled. The first 50 cc is therefore alone compared with the standards, and the colour is for example found to correspond with No. 2. Now No. 2 in the series shown above contains 075 cc NH 4 C1 solution. .*. All the free or saline NH 3 in 500 cc of the water 075 = 075 cc 4- - this ~ 075 + '25 which zr i cc 3 but i cc = 'oi milligramme NH 3 .*. 500 cc contain o'oi milligramme NH 3 and 100 cc ,, o - oo2 ,, ,, i.e., o'OO2 parts per 100,000 of free or saline ammonia. In the case of a water containing so large an amount of free ammonia that it gives a colour darker than any of the standards ; a portion of it must be taken and diluted up to 50 cc, the colour in this matched with one of the standards, and the amount of dilution taken into consideration. For example, the first 50 cc of distillate from a sample was so dark, that when compared with the standards there were none equal to it, 25 cc of it were therefore taken and diluted to 50 cc with pure distilled water, and then it was found to match No. 5, which contained 2'p cc NH 4 Cl solution .*. since this contained only 25 cc of distillate the 50 cc = 4-0 cc, and the whole sample = 4 + J = 5-333 which x by -oi = 05333 per 500 cc, divide this amount by 5, and we get '010666 per 100 cc, i.e., parts per 100,000. Lastly, to the residue left in the flask, which it is presumed contains some nitrogenous organic matter, is added 8? 50 cc of an alkaline solution of potassium permanganate and (some ammonia-free water must be added if the residue left in the flask has been much reduced by the previous distillation) then distil and collect the distillate in 50 cc Nessler tubes as was done in the first stage of the process. The alkaline permanganate solution is prepared by dissolving 200 grammes of KHO and 8 grammes of K 2 Mn 2 O 8 in 1200 cc of distilled water, which is then concentrated by boiling rapidly until when cool it measures i litre, this should be kept in a well stoppered bottle ready for use. Before use, as an additional precaution, it is a good plan to place 50 cc of the alkaline permanganate in a flask with 100 cc of pure distilled water, and boil for ten minutes, the alkaline permanganate is then free from all NH 3 (possibly absorbed since it was first prepared), and this solution can now with safety be added to the residue in the flask and distillation commenced. As distillation proceeds, the distillate is collected in 50 cc Nessler tubes, previously numbered, and these, when all the ammonia has distilled over (which is ascertained by testing a little of the distillate in a test tube, with a few drops of Nessler's solution) are compared with the standards, only in this case, each successive 50 cc must be matched, and the total amounts of NH 4 Cl to which they are equivalent ascertained. For example : No. i distillate matches No. 3 standard. No. 2 ,, ,, No. 2 No. 3 ,, No. i ,, No. 4 ,, contained no NH 3 Then all the NH 3 derived by the use of the alkaline permanganate solution equals : i cc + 0*75 cc + 0*5 cc of NH 4 Cl solution. i.e. 2-25 cc. and each i cc = x>i mgm. NH 3 .'. 500 cc of the sample contained albuminoid or organic ammonia equivalent to 2.25 cc of NH 4 Cl solution, and since each i cc = 0*01 mgm. NH 3 , therefore 2*25 cc NH 4 Cl solution = 0*0225 mgm. NH 3 i.e. 500 cc = 0*0225 mgm. NH 3 and 100 cc = 0*0045 ,, ,, i.e. 0*0045 P ai "ts albuminoid ammonia per 100,000. In regard to the conclusions to be drawn from the above estimations, all rain or snow-water, especially that collected near a town, shows a certain, and often considerable amount of free ammonia, as a rule it amounts to about 0*028 part per 100,000; but this rain-water, if not further contaminated by the washings off roofs, surface washings, or other pollution, will show little albuminoid ammonia. 88 The water from shallow wells will, if uncontaminated, show little or no free ammonia, and only a trace of albuminoid ammonia. All the ammonia which reaches the soil, if the process of filtration through the superficial layers of the earth be uninterrupted, is seized by plant life for its support, but if the natural process of filtration be interfered with, and water which has not undergone this process of natural filtration through the superficial 1 ayers of what has been cal led the ' ' living ' ' earth gets into the well, then the free and albuminoid ammonia will be present, and present in large amounts, so that in the case of shallow well-water, a large amountof free andalbuminoid ammonia always means that unfiltered filth, that is filth which has not been exposed to the nitrifying ferments, has gained access to the well. The circumstances under which filth may gain access to a well without undergoing natural filtration, are where a leaky drain allows its contents to flow beneath the superficial layers of the earth, or where there is a leaky cess-pool, etc., or where the surface washings from manured land gain direct access to the water supply, as often happens, in unprotected water supplies. There is afso another source of pollution which must not be overlooked, this is the case where the water supply is intermittent. Pipes alternately full and empty are very liable, if there be a leak, to suck in any liquids or gases through which the pipes may pass, just as a Bunsen lamp draws air into it when it is alight. The conclusions to be drawn in the case of waters from deep and shallow wells are different. In deep wells the amounts of saline ammonia are frequently somewhat excessive, and these may be disregarded if unaccompanied by other evidence of pollution, although these amounts would, as we have already said, if present in a shallow well, justify the condemnation of the water. The origin of the ammonia in deep well waters is the subject of much speculation ; in some cases it may be due to ammonia salts deposited in the deeper layers of the earth, or what is more likely, is that it is due to nitrates in solution coming in contact with iron salts, which act as reducing agents. The pipes which carry water have been known to act in this way, and it is of great importance to determine whether iron is present, even in traces, in the case of a water showing much saline ammonia. Deep wells, uncontaminated, showing much saline ammonia would show little or no albuminoid ammonia, and other evidence of contamination by animal organic matter would be wanting. Bearing in mind these facts, we must consider albuminoid ammonia as the important substance upon which a water's reputation stands or falls, albuminoid ammonia indicates present danger, its source must therefore be determined, if of -vegetable origin and relatively unimportant as in peaty waters, it will distil over gradually, there will be small amounts of chlorides and little or no oxidised nitrogen ; when of animal origin, and therefore dangerous, it w r ill distil over rapidly, principally in the first two 50 cc tubes of distillate, and this will be accompanied by much free ammonia, and the presence of chlorides and oxidised nitrogen as nitrites and nitrates. Free ammonia in a polluted water is due as a rule to urea which, as is well known, is speedily hydrated and converted by means of the micrococcus ureae into ammonium carbonate. Wanklyn says " when the free ammonia exceeds o'o8 part per million, it almost invariably proceeds from the fermenta- tion of urea into carbonate of ammonia, and is a sign that the water in question consists of diluted urine in a very recent condition. In these cases the water will likewise be found to be loaded with chlorides." These waters will also show an excessive and generally very excessive amount of albuminoid ammonia. A small amount of free ammonia and albuminoid ammonia not exceeding o - oo8 of albuminoid ammonia will generally indicate an uncontaminated water. Free ammonia amounting to 0*005 part per 100,000 and albuminoid ammonia amounting to o'OoS will generally indicate a water just on the border line, if there be excess of chlorides and nitrates, the water will generally be found to be contaminated by animal organic matter ; if not, and there is no evidence of contamination, it mny be considered fit for use. Much albuminoid and little free-ammonia, accompanied by small amounts of chlorides and oxidised nitrogen, points to vegetable contamination, and frequently indicates water from an upland surface where peat abounds. The following table is a summary of conclusions based upon the amounts of free and albuminoid ammonia found : Amounts in parts per 100,000. Free NH 3 Albuminoid NH 3 Conclusions. Nil Considerable, say o'oi Probably of vegetable origin such as peat. Much free, say o'oi Little or none under 0*003 Probably rain water O'OO2 or under 0.008 Water pure 0-005 O'ooS Probably pure, but on border-line of safety O'OI O'OI Very suspicious, probably polluted with urine O'ooS or over O'OI Urine or "sewage go Nitrates. These salts represent the ultimate stage of oxidation of nitrogenous organic matter, and therefore indicate old rather than recent contamination. In certain strata nitrates are present, and it is impossible to say how long a time they have been where they are, possibly they have arrived there by a process of infiltration or diffusion ; the whole process of diffusion of salts through porous soil is most complicated, certain salts diffuse quickly, others diffuse very slowly. Nitrates in a water are usually present as nitrates of soda, or lime, more rarely as nitrate of potassium, and in analytical results one generally expresses nitrates as N 4 O 5 since nitric acid may be regarded as N 4 O 5 +H 2 O 2 HNO'/, calcium nitrate as N 2 O. + CaO = Ca(NO 3 ) 2 , sodium nitrate N a O 5 + 2Na + H 2 O = 2 NaNO 3 + 2H. Nitrates expressed as N 2 O s should not exceed 5-5 parts per 100,000. 5'5 X 27-88 Expressed as nitrogen this would be = 1*43 N 107-28 i.e. taking the atomic weight of N as I3'94, and that of O as 15-88. There are several methods of estimating nitrates present in water. Two of the methods, the Aluminium and Zinc- copper couple depend for their action on the fact that in these processes nascent hydrogen is formed, which acts as a reducing agent, converting nitrates into ammonia thus HNO. + 4H 2 - NH 8 + 3 H 2 O. In the aluminium process a strongly alkaline solution is made by dissolving 100 grammes of pure NaHO in a litre of distilled water, to which is added about six square inches of aluminium foil, which has been heated to just short of redness by wrapping it round a piece of glass rod, and holding it for a few seconds in the flame of a Bunsen or spirit lamp ; the solution is then corked and left for some hours. The object of adding the aluminium foil to this, is to ensure the conversion into ammonia of any nitrates accidently present in the reagent, ammonia so formed is then removed by boiling, and the solution is once more made up to the litre with pure distilled water known to be free from all trace of ammonia. A solution of one of the caustic alkalies in water has the power of attacking metallic aluminium, with the result that hydrogen is evolved ; this reaction may be represented as follows : Al, + 2 NaHO + 2 H 2 O = Al, Na 2 O + 3 H 2 . Aluminium, caustic soda and water yield aluminate of soda and hydrogen gas. The second part of the reaction in which the nitrate is reduced, is represented thus ; where M f signifies an univalent metal 9 1 4H, + M'NO 3 = NH 3 + M'HO + 2H.O. Hydrogen and nitrate, yield ammonia, a hydrate of the alkaline base, and water. Detail : Add to 100 cc of the sample water in a flask 100 cc of the alkaline solution, previously described, and also about two square inches of aluminium heated to just short of redness in the manner already mentioned ; cork up the flask and set aside for some hours, at the end of which, distil as in the Wanklyn process. The qualitative tests will have shown whether or not there is likely to be a large quantity of ammonia resulting from the action of this process, if there is, distil over about 120 cc, mix the distillate and take a certain portion of it, say 10 or 20 cc, make up to 50 cc with distilled water, add 2 cc Nessler's solution and compare with standards as in the Wanklyn process. Before estimating the nitrates by this method, it will be necessary to know how much free ammonia the water contains, and also what quantity of nitrites exists in the water. These amounts expressed as N H 3 must be subtracted from the N H ~ found by the aluminium process, and the result will be ammonia derived from the reduction of nitrates, which can then be expressed either as nitric nitrogen, N, or as N 2 O 5 . An example will perhaps make this clear : After employing the aluminium process, 120 cc w r ere distilled; as the sample contained a good deal of nitrates, only 20 cc were taken ; this quantity diluted to 50 cc, Nesslerised, and compared with the standards as detailed, was found to match the standard containing 2 cc of NH 4 Cl solution. i.e., 20 cc of the 120 cc = 2 cc NH 4 Cl solution .'. 120 cc :0 = 12 cc, but each i cc = '01 mgm. NH 3 . 20 .'. 12 cc = '12 milligramme NH^ in 100 cc of the sample water since there were only 100 cc of the actual sample taken. Now all of this NH 3 is not attributable to nitrates, for let us assume 0-005 milligramme per 100 cc of free ammonia were found in the water and 0*056 milligramme NH 3 were derived from nitrites present, that is to say 0*005 + 0*056 which = 0*061 must be subtracted from the total 0*12 milli- gramme, leaving 0*059 milligramme per 100 cc of NH 3 derived from nitrates. To express this as nitric N, we must multiply by 14 and divide by 17, because N : NH 3 I! 14 : 17 and to express it as N ? O fi we must multiply by 108 and divide by 34, because 2NH 3 :N 2 O 5 :: 34: 108, or in other words multiply; by W which = 3*176, so that in the above example the nitric 92 nitrogen would have been 0*048 per 100,000. and nitrates as N 2 O 5 would have been 0*1873 P er 100,000. Zinc-copper couple ; this process requires a certain amount of saline matter in the water in addition to any nitrates, which were first ascertained to be present by the qualitative tests, so that in the case of very soft waters a small amount of pure sodium chloride (0*1 gramme per loocc) should be first added. Apparatus required. A 6 ounce wide-mouthed stoppered bottle, some zinc foil, and a solution of cupric sulphate, made by dissolving 30 grammes copper sulphate in a litre of distilled water; distilling apparatus and Nessler glasses as in the Wanklyn process. Detail : Having cut a piece of clean zinc-foil about 3 inches by 2 inches, immerse it for about three minutes in the copper sulphate solution, then pour off the copper solution and wash the zinc (which must be firmly coated with a deposit of metallic copper, black in colour), first with pure distilled water, and then with sample water. Into the wide-mouthed stoppered bottle put the zinc (which, prior to the coppering process, has been corrugated by folding it several times, and then pulling it out again), add 100 cc of the sample water, close the bottle with the stopper and place it in a warm cupboard (temp. 25 to 3OC.) for at least 12 hours, after which transfer the water to the flask of a distilling apparatus, add 200 cc of pure ammonia-free distilled water, distillation is then commenced and the distillate collected until the NH 3 has come over, an aliquot part of this distillate which was collected in a receiving flask is then taken and Nesslerised, and the calculation and deduction for free ammonia and nitrates previously estimated is made as detailed under the description of the aluminium process. A colour method for the estimation of nitrates, which is very simple in mode of action, is conducted as follows Apparatus. Two platinum dishes capable of holding at least 70 cc, three clear glass cylinders of uniform calibre capable of holding 100 cc, with a mark at 100 cc, a graduated measure, and the following reagents /. Phenol-sulphonic acid, made by taking 37 cc of strong sulphuric acid (free from nitric acid) and adding to it 3 cc of distilled water and 6 grammes of pure phenol. //. Liquor ammonia. S.G. 0*891. ///. Standard solution of potassium nitrate, made by dissolving 072 gramme of KNO 3 in a litre of water i cc = O'i milligramme of nitric nitrogen. thus KNO a N 38-83 + 13-94 + (15^)3 contams 13-94 93 loo 4i .*. i gramme of N is contained in z= J'2O^ gms. KNO S T 3'94 .'. if we take 072 gramme KNO :1 and dissolve it in a litre of water i cc will contain O'oooi gramme of N, i.e. OT milligramme N. IV. Pure sulphuric acid. I'. Pure ammonia-free distilled water. The test is performed thus (having first determined qualitatively whether there be a large or small quantity of nitrates in the water), (a} take from 20 to 100 cc of the sample, place it in a platinum dish and evaporate to dryness over a water bath, (b} in another platinum dish place either 5 cc or 10 cc ot the standard nitrate solution, evaporate to dryness over a water bath. To (a] and (b} add 2 cc of phenol-sulphonic acid solution, thoroughly mix with a clean glass rod, and then add to each i cc of distilled water and 3 drops of strong sulphuric acid, and warm for a few minutes over the water bath, after which to each add 25 cc of strong ammonia, pour into the 100 cc tubes, taking care to label each one as it is poured out, then make up each to 100 cc with pure distilled water, if they match in colour there is nothing more to do but calculate the amount of nitrogen, if they do not, and (a) is found to be darker than (b), take a third 100 cc tube exactly similar to those previously used, and pour into it sufficient of the fluid in tube (a) to give a depth of colour matching (b} ; say for example 30 cc of (a} matched the standard (), and (a) contained the residue from 50 cc of the sample of water evaporated to dryness, and (b} contained, let us say 10 cc of potassium nitrate solution which is equal to i milligramme of nitric nitrogen. 30 cc of a = i milligramme N 50 x i /. 50 cc = - - = f = 1-66 30 .'. 50 cc of the water contain nitrate equal to r66 milli- gramme of nitrogen, and 100 cc will contain 3-32 milli- gramme, i.e. 3-32 milligramme per 100,000, an amount which is generally allowed to be excessive. A water should not contain nitrates to the extent of more than 1-428 part per 100,000 expressed as nitric nitrogen (N), or expressed as N 2 O 5 , nitrates should not amount to more than 5-51 parts per 100,000. In judging the colours in colorimetric analysis, advantage is taken of the fact that in solutions which are coloured by the same substance, the depth of colour is dependent on two 94 things, degree of concentration and height of the column viewed ; now if one of these contain a known amount of the substance, and these solutions be placed in clear glass cylinders of equal calibre, similar in fact in every respect, then the degree of concentration can be determined by noting the depths of fluid which causes the tints of colour to coincide, as an experimental proof let us take a solution of methylene blue O'ooi milligramme per litre, and put this in a tube 12 c.m. high, then take some solution of the same substance, but twice as strong, in this case the same tint will be seen as we got with the first solution but. with a depth only equal to 6 c.m., by this it is known that an equal volume of this solution contains twice as much of the colouring matter as the standard, since the same colour is given with a column only half as deep. Take another case, if 50 cc of the solution under examination give a match with 100 cc of that first mentioned when placed alongside one another under precisely similar conditions in regard to light Fig 32 STOKES' COLORIMETER. and containing vessels, then it may be assumed that the sample under examination is twice as concentrated as the standard, since half the quantity when placed in a cylinder of size equal to that holding the standard fluid, gives the same depth of colour. The results obtained by this method are sufficiently accurate to be relied on. For cplorimetric analysis, a special apparatus, depending for its action on these facts, and known as Stokes' colorimeter (Fig. 32), has been devised, which enables one to alter the level of the fluid in a standard tube 95 by means ot a moveable tube supported by a metal arm, this tube is placed in connection with it by a rubber tube carrying a pinch-cock, and at the same time one can read off the volume of the standard which gives the same depth of colour as the known volume of fluid under examination, the strength of which we are trying to ascertain. Nitrites. Except in the case of rain-water, which often contains nitrites in solution derived from nitrous acid present in the air, traces of which are known to be present after electrical disturbances, nitrites invariably indicate animal organic pollution, and waters containing nitrites must have suffered very recent pollution, since nitrites are formed prior to the more complete oxidation into nitrates. If the qualitative tests show nitrites to be present, it is advisable to rind out the extent to which they are present ; this may be done either by Griess's method or by llosvay's test. Griess's test depends for its action on the formation of Bismark Brown with metaphenylene-diamine if nitrites are present, and requires for its performance a burette graduated to o'i cc ; two i cc pipettes ; six 100 cc glass cylinders of uni- form calibre with a mark at 100 cc. Reagents : /. Dilute sulphuric acid (i : 2 of water). //. Solution of metaphenylene-diamine, 5 grammes in a litre of water, slightly acidified with sulphuric acid. ///. A solution of sodium nitrite of such a strength that i cc contains o'oi milligramme N 2 O 3 . It is impossible to get the required solution by dissolving the sodium or potassium salt directly, so the solution has to be made as follows : 0*406 gramme of dry silver nitrite is taken and dissolved in hot water, then pure" sodium chloride added, until it ceases to form a precipitate, and the solution is next made up to a litre with distilled water, this is set aside in the dark until it has entirely cleared, then 100 cc of the clear solution are decanted carefully and diluted to i litre ; i cc will contain o'oi milli- gramme N O 3 . To perform the estimation, take 100 cc of the sample water, add to it i cc of the sulphuric acid solution and i cc of the metaphenylene-diamine solution, mix and set aside. Now prepare with distilled water standards, con- taining 0-5, ro, i '5, and 2'O cc of standard sodium nitrite solution and add the same amounts of the solutions i and 2 at> were added to the sample, compare the colours, and if the sample matches one of them the calculation is simple and ob- vious, since we know that i cc = 0*01 milligramme of N O 8 96 if it matches the one containing 0-5 cc, the water contains 0*005 part per 100,000 -of N* O 3 ; or if for example it matches the 2'o cc. one, then o'O2 part per 100,000; if it is darker than any of these, an aliquot part of the 100 cc should be taken, say 10 cc, 20 cc, 25 cc, or 50 cc, and the amount of colour in this amount compared with the standards as described when speaking of the colorimetric method and using Stokes' colori- . meter. For example, let us .say that 10 cc, i.e., one tenth of the original 100 cc to which were added i cc of each of the reagents (acid and metaphenylene-diamine), matches the i'5 cc solution, in which case if 10 matches 1*5, 100 will match 15-0, i.e., the water contains 15 x '01 milligramme N 2 O 3 , or O'i5 part per loo'ooo. Another mode of estimating nitrites is the method known as Ilosvay's, which depends for its action on the fact that if we add a solution of sulphanilic acid C 6 H 4 (NH a ) SO 3 H (obtained by heating aniline with fuming sulphuric acid) to a water containing' nitrites, diazo-benzene-sulphonic acid C 6 H 4 Csof ) ls formed, and this, on the addition of a solution of alpha-naphthylamine CioH 7 NH 2 , forms a pink colour. The test is performed as follows :- In 100 cc of distilled water place i cc of the standard sodium nitrite solution, call this A; take 100 cc of sample water, call this B; to both A and B add 2 cc of the sul- phanilic acid and 2 cc of alpha-naphthylamine solutions, after five minutes compare A and B ; the colours are then equal- ised by diluting one or the other and taking a careful note of the degree of dilution, and the calculation performed, as in other similar cases. Example : A is lighter than B, and B has to be diluted to J, i.e., 25 cc of B when made up to 100 cc, give a colour matching that of B, .'. B contains four times as much N* O. as A, but A contains o - oi milligramme of N 2 O 3 , . ' . B con- tains 0-04 milligramme N 2 O 3 , i.e., 0-04 part per 100,000 of N 2 O 3 . Oxidisable Matter in water may be organic or inorganic, the organic being sub-divided into animal and vegetable. In order to form an estimate of the amount of oxidisable organic matter in water, advantage has been taken of the fact that potassium permanganate is capable under certain circum- stances of parting with its oxygen to this organic matter, the circumstances most favourable being an acid medium and a certain degree of warmth. Forchammer devised a process which Tidy improved upon, and this is the process generally adopted for estimating oxidisable matter. In regard to the acid, 97 diluted sulphuric acid is the best to employ, other acids would interfere with its action, more or less ; take for example the case of hydrochloric acid, if hydrochloric acid is too con- centrated, or too warm, it becomes decomposed, and free chlorine is given off, which acts as a reducing agent upon the per- manganate this would render it impossible to get even an approximate estimate of the organic matter present. Dilute sulphuric acid on the other hand has no such defect and it also prevents the formation of hycfrated maganese dioxide, and holds maganous oxide in solution. The substances which per- manganate has no effect on, are, amongst others, sugar, gelatine, urea, and creatin ; permanganate is reduced by iron, sulphides, and nitrites, but these, if present in a water, would be readily detected by the qualitative tests, and any oxygen given up to them could be allowed for. Vegetable organic matter, which is of course of vastly less importance than animal organic matter, is much more readily oxidised, and this is the principal argument against the use of potassium permanganate for the determination of oxidisable matter in water, but on the other hand the estimation by per- manganate when carefully performed is of great value as giving an estimate of the purity of the water w r hich is valuable for purposes of comparison, since, apart from the cases of upland surface water containing much peat, the amount of oxygen absorbed by waters of undoubted purity varies within very narrow limits ; speak'ing generally, a good water should not require more than 0*285 to o'357 part per 100,000 of oxygen to oxidise the organic matter present, and, as a general rule, a good water will not require more than half these amounts. Detail of the Tidy-Forchammer process : Requirements. Two 12-oz. stoppered bottles made of clear white glass ; a burette graduated to A cc ; and two i cc pipettes. Reagents : (i). Standard solution of potassium permanganate, i cc of which contains O'oooi gramme, i.e., O'i milligramme of available oxygen, this solution is made by dissolving 0*395 gramme of potassium permanganate in a litre of distilled water. (2). Dilute sulphuric acid made by taking i volume of pure sulphuric acid, diluting it with 3 volumes of pure distilled water, and dropping in potassium permanganate solution until a permanent pink colour persists after the acid solution has been warmed to 80 F. for four hours. 98 (3). A solution of potassium iodide (i in 10 of water) free from iodate, best obtained by recry stall! sation from a solution in alcohol. (4). Sodium thiosulphate (i.e., sodium hyposulphite) solution, i part of the " hypo " in 1000 of distilled water. (5). Starch solution (for use as an indicator), one part of starch rubbed up with 500 parts of water, then boiled for five minutes and allowed to cool, and, if necessary, filtered. The process is conducted as follows : Take 250 cc of distilled water, place it in a bottle marked A, and also 250 cc of the sample water, and place it in a bottle marked B. Warm A and B to a temperature of 267 C. (80 F.), then add to each 10 cc of the sulphuric acid solution and 10 cc of the permanganate solution, set aside in a warm cupboard or warm place w^here the temperature will remain constant at 80 F. The test should be done after the above treatment for 15 minutes, and another set similarly treated for four hours, in both cases, whether for 15 minutes or 4 hours, the method of titration is the same, and is as follows : Into A and B run a few drops of the potassium iodide solution, sufficient to destroy the red colour ; then into each in turn first run suffi- cient hyposulphite solution to nearly, but not quite, destroy the yellow colour due to the presence of free iodine liberated by the O 2 of the permanganate, then add a drop or two of starch solution ; a bright blue colour due to iodide of starch should now be seen ; after this more hyposulphite of soda is run in from the burette until the blue colour just goes, so that if we now add one drop of the permanganate solution the blue colour returns. Read off the total number of cc of " hypo " used for A, and repeat the process in an exactly similar manner with B, and note the number of cc used for it. In the case of very impure waters, or certain waters like upland surface w r ater containing peat, 10 cc of permanganate solution may be in- sufficient to give the water a pink colour which will last 15 minutes or four hours as the case may be, then it will be necessary to add more permanganate solution, and the amount so added in addition to the 10 cc must be carefully noted, and a like amount added to to the blank experiment with distilled water. The calculation is made in the same way whether the process has lasted 15 minutes or 4 hours, or whether 10 cc or more of permanganate have been added ; in general terms the calculation may be expressed thus : A R X x n X o'i x O'4 = answer in parts per 100,000. 99 In this case A =. the number of cc " hypo " used with 250 cc distilled in the control or blank experiment. B the number of cc " hypo " used with 250 cc of the sample water, n = the number of cc of permanganate solution added to the water, and this is multiplied by o'l, because each i cc K 2 Mn a O 8 solution contains OT milligramme of available oxygen, and this is multiplied again by O'4 in order to bring the result to parts per 100,000 (o'4 being the same as I) ; two-fifths of the amount found is taken because we took 250 cc of water and we require our results in milligrammes per 100 cc, because 250 : 100 :: 5 : 2. For purposes of illustration let us take an actual example : 250 cc of distilled water + 10 cc K* Mm O 8 solution required 30 cc of " hypo " to combine with the iodine set free from the iodide of potassium by the available oxygen in 10 cc of K a Mn 4 O s solution; in the case of distilled water where there is no oxidisable matter present, the available oxygen would be ro milligramme, so the amount of "hypo" used corresponds in this case, to i milligramme of oxygen. 250 cc of the sample water + 10 cc K 4 Mn O 8 required 25 cc of "hypo "to combine with the iodine set free from what remained of the available oxygen after a certain amount x of oxygen had been parted with to oxidisable matter present in the water. Then 30 25 which = 5 is the amount of oxygen parted with to organic matter in the 250 cc water in terms of " hypo," now it w r as found by the blank experiment A that 30 cc " hypo " are equivalent to 10 cc K Mn 2 O 8 solution, i.e., to i milli- gramme of oxygen. . . 5cc rr 3 *u of i milligramme O 4, i.e., 0*166 milligramme, and so '166 x 0*4 0*0664 milligramme per 100 cc, or 0-0664 part per 100,000. The reactions which occur during the various stages of this process are represented by the following chemical equations ist stage: K, Mn.O, +6H*SO 4 = 4 MnSO 4 + 2 K a SO 4 + 6 H 2 O + 5 O 2 Potassium permanganate and sulphuric acid form sul- phates of manganese and potassium, and water, whilst oxygen is set free to combine with any oxidisable matter with which it comes in contact. 2nd stage : Any oxygen remaining over and above that piven up to organic matter is available for the liberation of iodine from iodide of potassium added in the second stage, thus : IOO K, Mn. O 9 + 8 H 2 SO 4 + 10 KI = 6 K 2 SO 4 + 2 MnSO 4 4-8 H 2 O + 5 I a In the third stage. the amount of sodium thiosulphate solution (" hypo ") required depends upon the amount of iodine which has been liberated thus : 2 Na. SO 3 +1, -2 Nal + Na 2 S 4 O 6 Sodium thiosulphate and Iodine form sodium iodide (colourless) and sodium tetra-thionate. Lead in Water. Lead is a cumulative poison, and by reason of the small amounts of lead which are usually met with in drinking water, it is possible by prolonged use of a lead- contaminated water to at length reach a very severe stage of plumbism without the suspicions of the patient, or even the medical man, being at all aroused. There have been several severe outbreaks of lead-poisoning on an extensive scale where a plumbo-solvent water has been conveyed in leaden pipes, without the nature of the sickness being recognised until the analyst has detected lead, and then at once many cases of obscure sickness have become readily explained, and many well-known symptoms of plumbism, previously overlooked, have been observed. Palor, extreme debility, depression of spirits, mental derangements, dyspepsia, colic, and constipation are usually seen ; but Bright' s disease, gout, defective vision, and even blindness may occur after prolonged lead poisoning. It is most important then to understand the circumstances under which we are likely to find lead in a water supply, and, also to know how lead can be eliminated from, or better still, prevented from getting into a water-supply. Soft waters are those in which lead is usually found, but soft water requires either a certain amount of aeration due to dissolved oxygen or carbonic acid gas, or else a certain degree of acidity, and in addition certain salts such as nitrates and chlorides aid the solution of lead, this is particularly the case with ammonium salts ; the presence of decaying vegetable matter, especially peat, also favours this action. Oxygen in water a6ls by forming the hydrated monoxide Pb (HO) 2 when it comes in contact with metallic lead; car- bonic acid a6ls by rendering the otherwise insoluble PbCO 3 slightly soluble. Peaty waters owe their plumbo-solvent action to acidity, which is the result of bacterial growth. Two acidifying bacilli, named <1 P" and "Q" bacilli, have been isolated from peaty earth, and proved by experiment to be the offenders. Peaty water which has soaked into the soil and issued elsewhere at a spring exerts little or no plumbo-solvent 101 a6lion, because the bacilli have been removed by the filtration and the acidity neutralised by the alkaline bases of the soil ; peaty water on the other hand which has run directly out of a peat bog into a reservoir or into pipes has a remarkable power of dissolving lead. Houston was able to show that bacilli caused the water to become acid in the following way : he took some upland surface water, showing no plumbo- solvent power, then added to it a sterile decoction of peat, the water still showed no plumbo-solvent action, but when to this water he added a small amount of living peat earth, the water was quickly acidified. Waters containing the alkaline carbonates, such as calcium or magnesium carbonate, will not take up lead, since white lead, a mixture of lead carbonate and lead hydroxide Pb (CO.), Pb (OH) 2 is formed, this is an insoluble substance, which, being deposited on the metal, protects it from further change; likewise waters containing sulphates will not give rise to lead poisoning since lead sulphate (PbSO 4 ) is a very insoluble salt, and this is deposited on the pipes, and prevents further action.* One method of removing lead from a water-supply on a large scale consists in adding calcium carbonate to the water (3 grains to the gallon) ; another is to filter the water through some lime-containing medium, such as limestone, in addition to the ordinary medium employed by water companies for filtering on a large scale. For domestic purposes, an animal- charcoal filter will efficiently remove lead by forming insoluble lead phosphate. Quantitative estimation of lead requires : Apparatus (i) burette graduated to A cc ; (2) Nessler glasses, 50 cc capacity, with mark at 50 cc ; (3) pipettes to hold 5 cc and i cc respectively. Reagents (i) pure distilled water; (2) dilute hydro- chloric acid; (3) sulphuretted hydrogen solution; (4) standard solution of lead, i cc of which = i milligramme of Pb, this is made by dissolving 1*575 gramme Pb (C 2 H 3 O 2 ) 2 in a litre of distilled water, because 354-27 parts of Pb(C2H 3 O 2 )a (lead acetate) contain 205-35 parts of Pb (lead) therefore the amount of lead acetate equivalent to i part of lead is 35427 __ ~ l 575- Detail : add to 50 cc of the sample water i cc of dilute hydrochloric acid and 5 cc of sulphuretted hydrogen solution, * Water containing 17-5 grains per gallon of Calcium Sulphate will only dissolve -05 grain of lead per gallon in 72 hours, but water containing 1-4 grain per gallon of Ammonium Nitrate will dissolve 1-75 grain per gallon in the same period. IO2 and add the same quantity of reagents to standards prepared containing various known amounts of lead ; with small amounts of lead greater accuracy is possible than with larger amounts, and since, as a rule, a water only contains minute amounts of lead, this method is sufficiently accurate for an ordinary hygienic analysis. Example : 50 cc of the water and reagents as noted matches standard containing 0-5 cc of standard lead solution, i.e., 50 cc contains O'5 milligramme of lead, and 100 cc con- tains i milligramme of lead, i.e., i part per 100,000 or o'j grain per gallon. House Refuse an indication of pollution. If there be any sediment, it is collected by allowing the sample of water to stand some hours in a cylinder a glass having a conical bottom with rounded apex pointing downwards a portion of it is removed with a pipette, and a drop placed on a slide and examined with an inch or j-inch objective. There are certain substances which are sure to find their way into water if either sewage or house refuse which includes slop-water and refuse from scullery sinks gain access to the water supply. These substances we have already enumer- ated, it remains to describe those most commonly found. Cotton may be met with as woven threads, when the unaided eye would recognise them, or small portions of cotton fibre, such as become detached from calico cloths, etc., may be found by the microscope, when they appear as thin taper- like bands twisted on themselves ; these are readily stained by any of the basic aniline dyes, such -as gentian or methyl violet; they are not dissolved nor stained yellow by nitric acid, but when in contact with it, they become untwisted. Fig. 33 00- Wool. The fibres of wool are seen even under a i-inch objective to consist of rounded fibres with peculiar irregular imbrications ; in old wool fibres which have been frequently washed, these markings are often indistinct, but can generally be made out ; they stain readily, and are turned yellow by nitric acid. Fig. 33 (c). Silk fibres are structureless hyaline rods, in which occa- sional nodes are sometimes seen, when acted on by dilute mineral acids they first become indistinct, and then dissolved, they stain readily with any dyes, but especially well with picric acid. Fig. 33 (d). Linen fibres are cylindrical, and show transverse mark- ings at intervals, these are not always very clear, but small fibres are almost invariably seen coming off at various points, resembling the adventitious roots of certain creepers. Fig. 33 W- 103 Hair shows a cortical and medullary substance; light hair shows this less markedly than dark hair ; nearly all hair shows imbrications more or less ; in the hair of rabbits and cats, and in that of some human subjects, these are well marked. Fig 33 (it). Epithelial cells and muscle fibres need no description. Spiral vegetable cells, such as pieces of undigested cabbage, are also easily recognised. a. Cotton. b. Linen. Fig. 33. c. Wool. d. Silk. e. Hair. Starch cells. These consist of two substances, starch- cellulose and granulose, the latter staining blue with iodine, whilst the former is turned brown ; the characteristic appear- ance of the various starches is detailed in another chapter (vide pp. 168 175). 104 Bacteriological Examination. When possible a bac- teriological examination should always be made, but unless done with great care it is of little value ; there is no doubt that if one had to choose between two examinations of water, viz., a chemical and biological one, that in the great majority of cases a chemical analysis, carefully performed, would afford the more reliable information as to the purity of a water ; a chemical analysis will nearly always warn us of danger, but will, unfortunately, sometimes afford a feeling of false security: a bacteriological examination in many cases will fail to detect dangerous pathogenic microbes even after a prolonged and careful investigation, as, unfortunately, has been seen in several severe epidemics of typhoid fever. The general nature of the means employed for detecting pathogenic micro-organisms is here given : Firstly, the water must be collected with care, if possible in sterile vessels, if it is not possible to have absolutely sterile vessels, at any rate let them be free from any suspicion of being infected by pathogenic organisms. Secondly, since micro-organisms multiply exceedingly rapidly if the temperature be at all warm, the water should be examined at once, or the sample kept at as low a tempera- ture as possible until the examination can be made. Thirdly, it is assumed that a number of sterile test-tubes, sterile Petri's dishes, and the various apparatus connected with a bacteriological laboratory are available, also a supply of culture media, such as nutrient gelatine, agar-agar, and beef bouillon. We therefore proceed to describe the process for enumerating the micro-organisms in a sample of water, and separating r by means of plate cultures, suspicious colonies. Having sterilised a i cc pipette, it is filled up to the mark with the sample water, and one, two, or at the most four drops of the water are allowed to fall into a tube of liquefied gela- tine, the temperature of which feels warm but not hot when held in the hand (about 40 C.), this is rolled and agitated gently in order to ensure thorough mixing, and then poured out on to a small sterile glass plate, placed upon another sterile glass plate with a sterile cover, this is supported by a dish filled with ice and water, which rests upon a carefully adjusted levelling apparatus. If the plate has been carefully levelled the liquefied gelatine will readily flow in an even manner over the plate, but if not level it will overflow, and all the material and trouble will be wasted. Petri dishes, 10 cm. in diameter and r8 cm. deep, are more convenient and answer the purpose equally as well as, or even better than, the glass plates, these should be allowed to set on a levelling stand over ice, in order to ensure an even distribution of the gelatine and a speedy solidification. The plates or dishes are, when set, placed in a sterile glass chamber in a cool situation, where the temperature will not exceed 22 C. Gayon's flasks are frequently used in lieu of the glass plates or Petri dishes, these are figured in various catalogues. After two or three days colonies will appear, every colony representing one parent microbe, so that by counting the colonies over a microbe counter (which can be improvised by the worker, or he can employ Wolfhugel's, in which a glass plate 12 cm. square is sub-divided into squares of i cm., and some of these are again sub-divided into 9 smaller squares) we find the number of microbes contained in the quantity of water taken, and these are counted and noted from day to day until liquefaction has occurred, and any peculiarities of growth noted. In regard to the amount of water taken it is important to know what fraction of a cc was taken ; this is found by seeing experimentally how many drops are delivered per cc by the pipette used, and then we note on the culture the name of sample, date, medium, the number of drops used as a fraction in which the denominator is the total number of drops per cc which the pipette delivers ; a convenient method is to use a pipette made to give a definite number of drops, or if the water be one likely to contain many microbes, take say i cc of the sample and add this to a sterile test-tube containing 9 cc of sterile water, we shall then have a i : 10 solution of the water ; if now we take A of i cc of this water and introduce it by means of a drop-counter into a tube of nutrient gelatine, we shall be working with -nW * cc of the original water, and the number of microbes found in the plate culture multiplied by 100 will be the number per cc. Npw-a-days plate cultures are made more with a view to isolating special species than to enumerating the microbes. Miquel, however, has laid down a scale of purity based upon the number of micro-organisms found at the time of collection, thus : o to 10 germs per cc show a water to be excessively pure. 10 to 100 germs per cc show a water to be very pure. 100 to 1000 germs per cc show a water to be pure. 1000 to 10,000 germs per cc show a water to be of medium purity. 10,000 to 100,000 germs per cc show a water to be impure. More than 10,000 germs per cc show a water to be very impure. A larger number of micro-organisms in a water snows either that surface washings or sewage are gaining excess to the water-supply. A deep well should show very few micro- organisms. * A further dilution might be made with advantage in the cases of very polluted waters. io6 The chief pathogenic organisms known to be spread by water are those of cholera and typhoid fever. Cholera is readily detected. MetchinkofFs method is that in which 200 cc of the water are taken and placed in a sterile flask capable of holding a little over 250 cc, and then the following solution is added, after being previously sterilised, it consists of 2 grammes best peptone, 2 grammes sodium chloride, 4grammes gelatine, and sufficient solution of sodium carbonate to render the solution slightly, but nevertheless clearly alkaline, and then distilled water is added to make it up to 50 cc. The sample, after this solution has been added, is incu- bated at 37 C., at the end of eight or ten hours a distinct pellicle will form on the surface if the vibrio of Asiatic cholera is present, from this, gelatine stab cultures should be made, when the growth which occurs is characteristic; after 24 hours liquefaction is seen to be commencing all along the needle track, and at the point of entrance the liquefaction is rather more marked and encloses a bubble of air; in a gelatine culture of Finkler-Prior's vibrio the needle track is more funnel- shaped at this period, which distinguishes it from the vibrio of Asiatic cholera. The microscopic appearance of the vibrio of Asiatic cholera is well-known, comma-shaped curved rods, 1*5 to 3 fj. long and 0*5 to 0*6 /x broad, which stain well with Ziehl-Neelsen fuchsine diluted three or four times with water, or with a weak watery solution of methyl-violet, but they are not stained by Gram's method. The grouping of the bacilli is another distinguishing feature ; in each collection of bacilli the individual bacilli point the same way. The vibrio of cholera gives the indol reaction, or cholera-red. If the culture contained nitrates, these are reduced to nitrites by the cholera vibrio, and on the addition of a drop of strong sulphuric acid a red colour is produced, or it may be obtained by adding to a broth culture tube con- taining the vibrio of cholera the following substances : First, i cc of a solution of potassium nitrite 0*02 per cent, strength, and then slowly i cc of pure H 2 SO 4 diluted with three parts of water ; if the culture contains indol a rose-colour is seen. The bacillus of typhoid fever usually gains access to a water-supply through defective drainage, and the detection of it is often a matter of very considerable difficulty, even in the case of sewer effluents known to be contaminated by typhoid excreta it has not always been found even after a prolonged and careful examination. The difficulty in isolating the bacillus may possibly be due to the facl; that typhoid fever bacilli are only met with in the stools of typhoid patients when Peyer's patches are ulcerated, that is to say about the ioy middle of the second week of the disease, and according to Besson it is only met with in the urine of patients suffering from typhoid fever when the urine is albuminous, for as soon as this ceases to contain albumen the bacilli disappear. Besson found it in 40 per cent, of typhoid cases where the urine contained O'i per cent, and upwards of albumen.* Various methods have been devised, such as incubating some of the suspected water (20 to 100 cc) with sterile beef broth at a temperature of 45 C. ; at 45 C. most micro- organisms cease to multiply, whereas the bacillus coli and Eberth's typhoid bacillus will; if then the broth becomes turbid in from 20 to 24 hours these micro-organisms are sus- pected and plate cultivations should be made, preferably with nutrient gelatine to which carbolic acid has been added in sufficient extent to amount to O'OO2 per cent., this small amount of phenol restrains the growth of liquefying organisms and enables one to pick out colonies of the typhoid fever bacillus and those of the bacillus coli. Parietti's method for isolating typhoid fever bacilli con- sists in adding from 3 to 9 drops of the following solution to 10 cc of sterile broth or liquefied nutrient gelatine : Carbolic acid, 5 grammes ; hydrochloric acid, 4 grammes ; distilled water, 100 grammes. If broth be employed, this should be incubated at 41 C., if gelatine, at 20 C. to 22 C. Eisner's medium is now usually employed for cultivations with suspected water, upon it the bacillus coli and Eberth's bacillus grow freely, and can be picked off and planted out, it is, according to Besson,* prepared as follows : (i). 500 grammes of potato are peeled and grated. (2). The pulp thus obtained is macerated in a litre of water for three or four hours. (3). It is then strained, left for one night, and decanted. (4). The volume is made up to 1000 cc, and 150 to 200 grammes of gelatine are dissolved in it \vith the aid of gentle heat; when dissolved it is boiled for some minutes. (5). The liquid is very acid, this acidity is therefore reduced by the addition of a little sodium carbonate solution, so that it shall still be acid, but only to a slight extent. * The presence of typhoid fever bacilli in the urine of sufferers from typhoid fever, has lately been thought to be due to stray bacilli becoming lodged in the folds of the mucous membrane of the bladder ; it is assumed that these bacilli are brought in the blood to the kidneys and from there conveyed to the bladder in the urine, where, under favourable conditions, they rapidly multiply and get washed away from time to time during micturition. io8 (6). Heated to 115 C. for five minutes, and filtered warm. (7) . Returned to the flask and sterilised at a temperature between 112 and 115 C. A series of test tubes containing 19 cc of the above medium are sterilised in an autoclave, and also the following solution, consisting of 10 grammes of potassium iodide in 50 grammes of distilled water. When required for use, to each tube of potato-gelatine, liquefied at a gentle heat, is added i cc (20 drops) of the iodide solution, in this way we obtain a gelatine containing i per cent, of iodide. To each of the tubes thus prepared is added some drops of the suspected water, then the contents of the tubes are poured into Petri dishes and allowed to set; six or eight plates ought always to be prepared, which are incubated at 20 C. Opaque rounded colonies of the bacillus coli appear on the second day, whereas typhoid bacillus colonies only appear on the fourth day, and are then transparent, and scarcely visible ; according to Eisner, colonies of other bacteria are not noticeable at this time, but as a matter of fact colonies of other bacteria are present, and the colonies of bacillus coli and bacillus typhosus are by no means so distinct; the great advantage of Eisner's medium in the words of Besson lies not in any specific power which permits the growth of bacillus coli and bacillus typhosus and excludes others, but only in the fa6l that bacillus coli and bacillus typhosus can grow side by side. To differentiate between the bacillus coli and typhoid bacillus : Method of culture. Bacillus coli. Typhoid bacillus. (i). Grown in beef broth Numerous No gas set free. at 38'5C., containing bubbles of gas, . lactose carbonate. set free in from 12 to 36 hours. (2). Gelatine shake cul- After 24 hours, No gas tures grown at 22C. copious gas formation. formation. (3). Culture in sterile Acidified and Acidified but milk. coagulated in not coagulated. 24 to 36 hours. (4). Broth culture. Shows indol No indol reaction. reaction. (5). Grown on potato. Thick brownish Culture trans- growth. parent and thin. *Page 40. Technique Microbiologique Bailliere et Fils, 1898. IOQ In cases where there is reason to believe that typhoid fever is attributable to the use of water sent for analysis, and the previous methods have failed to detect the bacillus typhosus, it would be well to filter a litre of the water under examination through a Pasteur-Chamberland or Berkefeld filter. It is necessary that the candle of the filter employed should be sterile, this having been assured, the water is caused to flow through one of the filters, this is done by connecting the nozzle of the filter with an air-tight flask capable of being connected with an air-pump ; when the water has passed through the filter it will be sterile, and all the micro-organisms contained in the quantity of w r ater taken will be deposited on the outside of the filter, pour 10 cc of the filtered water, which is now sterile water, into a sterile beaker capable of being plugged with sterile cotton wool, and, "with a soft sterilised tooth-brush, gently scrape the candle of the filter, so as to get as many as possible of the bacteria from the surface of the candle Into the beaker."* The beaker is once more plugged, and now contains a concentrated solution of bacteria ; a large series of phenolated gelatine tubes, previously prepared, are melted, and one or two drops of the solution of bacteria are added to each tube and plate cultures set. Sub-cultures are made if any colonies appear in these carbolised plates, and the presence or absence of typhoid fever bacillus is determined by microscopical examination, and the various tests performed by which differentiation between coli and typhoid bacilli is arrived at. In the microscopical examination typhoid fever bacilli if stained for by Van Ermengen's silver method show numerous flagellae, a single bacillus will often show as many as 17 or 18 long wavy flagellae, when stained by this method. Coli bacilli show very few, and these are shorter. Typhoid bacilli are straight and slightly curved rods with rounded ends, some appear to be oval. Coli bacilli are plump straight rods with rounded ends, and less motile than the typhoid bacilli. Both kinds stain well with the basic aniline dyes, but do not stain with Gram's method. * Practical Bacteriology by Kanthack and Drysdale. Ill CHAPTER V. METRIC SYSTEM OF WEIGHTS AND MEASURES. The metric system of weights and measures is univers- ally employed in all laboratories, notwithstanding that in water, and other analytical reports, results are often expressed in grains per gallon, grains per lb., etc. The meter was adopted as the unit of length, and thought to be the one ten millionth part of the distance from the equator to the pole ; this has since been found not to be strictly, although very nearly so, but this fact does not detract from its value as a unit of length. The fractions of the meter are termed deci-, centi-, and millimeters ; and the multiples, deca-, hecto-, kilo-, .and myriameters ; it will be seen that the first series are given Latin and the second Greek prefixes. If we remember that a meter is 39*37079 English inches, we can without difficulty remember the factor to divide or multiply by, when converting the meter measures into English inches, or English inches into meters or its fractions or multiples. For example : if it is required to know how many millimeters are equivalent to 30 inches, divide 30 inches by 0^03937, or multiply 30 inches by 25*4, and the result is found to be 762; or again it is required to find how many inches are equal to 60 centimeters, multiply 60 by 0*3937 or divide 60 by 2.54, and the result 23*622 inches. The unit of weight is the weight of a cubic-centimeter of pure distilled water weighed at 4C, the temperature of the maximum density of water, and this weight is called a gram, and in a similar manner, as with the unit of length, the fractions are called deci-, centi-, and milligrammes, and the multiples deca-, hecto-, and kilogrammes; and it follows, that a decigramme of pure water at 4 C C occupies the tenth of a cubic centimeter, a decagramme of pure water at4C occupies 10 cubic centimeters, and so on. 1000 cubic centimeters of water or fluids are generally spoken of as a litre. The weight of a gram in English avoirdupois weight is 15-43235 grains, but it is generally sufficient to remember the weight to three places of decimals, and then we have the weight of a gram as being equivalent to 15*432 grains, a number which, from the sequence of the figures, cannot be forgotten. 112 In using a chemical balance, there are certain points to be observed. The substance to be weighed is put in the left scale pan because we can place the rider on various points on the right beam without opening the case, as most balances are made for right handed people. The substance to be weighed must be cool, if warm, currents of air are set up- which cause the scale pan to oscillate, and so lead to error. The balance must be brought to rest before adding or remov- ing weights, the beam must be poised on the knife edge with the greatest possible care, the windows of the balance should be closed at the time of the final weighing, and the air of the cabinet which encloses the balance must be kept dry by means of a beaker containing some hygroscopic substance, such as calcium chloride or pure sulphuric acid. Specific gravity is the weight of a substance compared with the weight of an equal bulk of something else. As a rule, the term specific gravity refers to the weight of a sub- stance compared with that of an equal bulk of water, or in other words, its specific gravity is its weight in air divided by the loss of weight in water. The specific gravity of fluids is found either by employing a specific gravity bottle of known weight, capable of holding a known weight of water at a certain temperature (i5'5C). The bottle is fitted with a glass stopper and a counterpoise indicating the weight of the bottle is supplied with it. To find the specific gravity of the fluid, the bottle is filled at the 2fiven temperature (i5'5C), and the weight thus found is divided by the weight of water which the bottle holds. For example : a bottle which holds 100 grammes of water, when filled with oil holds 91-5 grammes of oil, so ~^ = 0-915, which is the specific gravity of the oil. Another method employed is to use an instrument called a hydrometer, graduated so as to show the specific gravity of the' liquid directly, the specific gravity being marked on the stem in the matter familiar to all. A third method employed, m the case of fluids shows the weight of the fluid displaced by means of a plummet suspended from a graduated beam, by noting the weight required to sink it to a certain mark which is indicated by riders of different sizes, each size being exactly one-tenth the weight of the next size larger. West- phal's'balance acts in this way and is a miniature '' steel-yard "' modified so that the beam is not suspended, but balances on an agate knife edge, the plummet used with it contains a sensitive thermometer and exactly displaces five grammes of distilled water at 15 C. "3 The plummet weighs 15 grammes in air, but only ten grammes in water because, as we have just said, it displaces five grammes (5 cc) of water, in order then to restore the level of the balance if the fluid in which it is suspended is water, or of the same density as water, a five gramme rider is fastened to the end of the beam which supports the plummet, and the balance is now seen to rest horizontally if the fluid in which it is suspended is heavier than water ; then, in addition, we shall have to put on more weights, and in the case of fluids lighter than water, less than five grammes will be sufficient, as explained further. The riders are of four sizes 5 grammes, 0*5 gr., 0*05 gr., and 0^005 gr., and the beam of the balance is 'divided into tenths, and riders are placed on the notches at these divisions until a perfect balance is attained. If a balance can only be attained by two or more of the riders being on the same division, these are suspended one from the other, the larger ones supporting the smaller ones. Fig. 34. WESTPHAL'S BALANCE. To make this clear let us take the case of a sample of milk having a specific gravity of ro29. In this case the five gramme rider, or No. i size, will hang from the end of the beam as it does when immersing the plummet in water ; the second size rider will hang from the No. 2 division of the beam, and the third size from the No. 9 division. That is to say, the plummet which in water displaces five grammes, in milk displaces 5 grammes i decigramme, 4 centigrammes, and 5 milligrammes, because a rider which weighs 5 grammes at the end of the beam will only weigh 09 x 5 at the 9th divi- sion, O'8 x 5 at the 8th, and so on. Similarly, the 0*5 gr. will at the second division weigh o'2 X 0-5 grm. = O'i grm., and the 0^05 grm. at the gth division will weigh 0*045 g m -> the amount of fluid (in this case milk) displaced, will weigh 5- 145 grms., and this divided by an equal bulk of water weighing 5'i45 5 grammes := = 1*029. 5'o In practice it is only necessary to read off the sizes and positions of the various riders, for we know that in using the balance we can read the specific gravity straight direct, since the first size at any division gives the first place of decimals of the value corresponding to the number of the division and whole numbers only when suspended from the end which supports the balance, the second size means the second place of decimals at any of the divisions, of the value of the number of the division, and so on. Thus, if using the balance the plummet sinks to the knot on the wire suspending it and the balance is horizontal, with the first size rider at the end of the balance, and the beam supports 2, 3, and 4, all hanging from the third notch, then the specific gravity will be 1*0333 if they had been placed the ist size at the end, the 2nd size on the 4th notch, the 3rd size on the 2nd notch, and the 4th size on the gth notch, then the specific gravity would have been ro429. If the specific gravity is less than that of water say O'Sgfj^-then the No. i size must be placed on one of the divisions (in this case the 8th), the 2nd size rider would be on the Qth division, and the 3rd size on the. 6th. The plummet which lost 5 grammes weight in water in this fluid only lost o'8 x 5 4-0 0-9 x '5 = '45 o'o x -05 =. -03 4-48 =: 0*896 = the specific gravity of the fluid in question. 5'0 For fluids considerably heavier than water, specific gravity is generally taken with Beaume's hydrometer, or areometer, and the density expressed in degrees of 'Beaume. Thus o Beaume = sp. gr. 5 ooo 007 014 020 028 34 Beaume' s hydrometers are constructed so as to show the density of fluid up to a specific gravity of 1-960, i.e. 72 Beaume's scale, and for light liquids, as low a specific gravity 0706. "5 CHAPTER VI. EXAMINATION OF AIR. COMPOSITION OF AIR. Pure Country. Vols. per cent. Oxygen ... 20-9 to 20-99 Carbonic Acid ... ... 0*0310 0*04 Nitrogen ... ... 79-0 (i per cent, of what was hitherto regarded as N, is now attributed to argon.) Aqueous vapour ... ... 0*4 to r6 (According to temperature) Ammonia ... ... Traces Ozone ... . ... Mineral substances ... ... ,, Organic matter ... ... Marsh gas ... ... ... M Air of Towns. Vols. per cent. Oxygen ... 2O'86 to 20-92 Carbonic Acid ... ... 0*04 to 0*05 Nitrogen ... 79-0 Aqueous vapour ... ... 0-4 to r6 (According to temperature) Ammonia ... Traces Sulphur Dioxide ... ... ,, Oxidised Nitrogen ... ... ,, Marsh gas ... ... ,, S Heavier traces than are met Organic matter ... \ with in pure country air. Carbon particles as spot Respired Air. Vols. per cent. Oxygen ... ... ... 16-033 Nitrogen ... 79'557 Carbonic Acid ... ... 4-38 Ammonia ... ... Traces Hydrogen ... ... ... Methyl Hydride ... ... Aqueous vapour nearly to saturation. n6 The object of an examination of air for sanitary purposes is to find out the nature of impurities and the extent to which they may be present. Impurities may be said broadly to be introduced in three ways : (i) Result of respiration ; (2) combustion ; (3) trade processes. It has been said that many of these impurities are present to such a small extent that it w r ould appear at first sight trivial to devote so much attention to them, the classic example ' which illustrates the importance of this attention will bear repeating. Suppose that an impurity of a hurtful nature (such as organic matter from the skin or lungs) be present to the extent of 0-019 per cent. ; o'oig per cent, is the same as 190 parts per million ; there are 70,000 grains in a gallon, so that if instead of expressing the impurity in parts per million, we express it in parts per 70,000, we can then think of it in grains per gallon. 190 per million is then seen to be equiva- lent to 13*3 per 70,000, or in other words 13-3 grains per gallon. Now 13-3 grains per gallon of organic impurity in a water would be considered an appalling amount, and it is improbable that a gallon of water would be drunk by one individual in a day, yet we breathe in daily between 1000 and 2000 gallons of air, and the extent of pollution quoted is often exceeded, so by this example we see very clearly how minute quantities of impurity present in the air, by reason of the large quantity of air breathed, become a grave source of danger. It has been found that the carbonic acid gas given off by respiration affords a valuable index to the extent of vitiation of the atmos- phere by respiration, but it must be clearly understood that the carbonic acid (CO 2 ), the result of respiratory pollution, is very different from CO a ,the result of combustion, and differs to a still greater extent from the C O 4 , the result of chemical pro- cesses, such as occur In the generation of C O 4 in the manufacture of aerated waters, etc. ; in the former case the oxygen is diminished and replaced by C O ft , and at the same time products, which are distinctly harmful, are added. In combustion, if the process is complete, C O 4 results, and re- places O 2 in the air, but nothing analogous to the hurtful organic matter given off from the lungs and skin is added. In the third case the C O z is added to the air and displaces its own volume of air as a whole, 79 per cent, of which is nitro- gen, so that even with comparatively large amounts of C O 4 thus added, the oxygen is not materially reduced. CO 2 , the result of respiration, should never be allowed to exceed O'O2 per cent., i.e., bringing the total amount up to '06 per cent, or '6 per 1000, whereas even i or 2 per cent, of CO 4 added in the manner indicated in the third case, might be borne with- out ill-effects. II 7 Examination of the air of a room. In examining the air of a room much may be learnt by the senses. If the CO 4 , due to respiration, does not exceed o - 2 Vols. per 1000, and the moisture is about 4*7 grammes per cubic foot, then the air will appear yr or if working with degrees Farenheith then we must 120 remember that gases expand -^ for every i F., and 32 F. = 459 absolute temperature. So combining these two laws we have V found x standard pressure. V required x existing pressure. Standard temperature in = Existing temperat-ure in absolute degrees. absolute degrees. So in the example given we have i x 760 x x 770 273 293 NOTE. In correcting for pressure, it is always easier to work with the height of barometer in millimeters instead of inches in order to avoid fractions. Inches may be converted into millimeters by dividing by '03937, or by multiplying the height in inches by .25-4- Or it can be stated thus i X 760 : 273 :: x x 770 : 293 i x 760 x 293 or = x 77 X 273 which worked out comes to ro5 cc. Analyst, p. 184, Vol. XVII. Dr. Gill estimates CO 2 by taking dry bottles capable of holding 4400 to 8800 cc, filling them with air with bellows, 15 strokes of which will fill a 4 litre bottle four times, thus ensuring a representative sample. 50 cc of barium hydrate solution are rapidly run into a bottle of air, the bottle is stoppered^ capped, and placed on its side and shaken at intervals for 40 or 60 minutes, at the end of which lime the cap and stopper are removed, the bottle in- verted over a 50 cc glass stoppered bottle so that the solution shall come in contact with the air as little as possible, 15 to 20 cc are withdrawn with a narrow stemmed 15 or 20 cc bulbed pipette and titrated with sulphuric acid (i cc of which. = i milligramme CO,), using rosolic acid as an indicator. The difference between the number cc of standard acid required to neutralise the amount of barium hydrate before and after absorption gives milligrammes of CO 2 present in bottle; milligrammes CO., can be converted into cubic centimeters as already detailed, the usual corrections for temperature also being made. NOTE. The acid may be prepared by diluting 46-51 cc normal H 2 SO 4 to a litre. Lunge and Zeckendorfs method. Another method which, like Pettenkofer's, depends for its action on the reduction of alkalinity of an alkaline solution exposed to CO 2 , is that known as Lunge and Zeckendorfs 121 method, the indicator, as before, is phenolphthalein, and the solution employed is -^ Na 2 CO 8 ; instead of adding the alkaline solution to the air, in this case we keep passing known quantities of air through the solution until the colour is discharged, the air is caused to flow through the 'solution by pressing a rubber ball which is connected with one of two tubes arranged like the tubes of a wash bottle, the rubber ball is practically a Higginson's syringe and like it, is furnished with two valves which cause the air to flow only in one direction ; it delivers 70 cc of air each time the rubber ball is filled and emptied. By noting the number of times the ball is compressed, and referring to a table furnished with the apparatus, the amount of CO 2 in the air is approximately ascertained. For example : If on compressing the ball twice the colour is discharged, this indicates that there are 3^0 parts per 1000 of CO 2 in the air; 20 compressions show that the limit of respiratory impurity has been slightly exceeded, viz., o'62 parts per 1000 of CO 2 in the air; and if the ball has to be compressed 35 times before the colour goes, then we know that the air of the room does not differ sensibly from the out- side air, viz., 0^42 parts CO 2 per 1000 of air. We mentioned in connection with this apparatus a solu- tion of Na 2 CO 3 -'- strength, this signifies that the solution is th of the normal strength ; a normal solution contains the hydrogen equivalent weighed in grammes of the active constituent of substance dissolved in a litre of water at 16 C. In the case of a univalent substance, the atomic weight (or in the case ot a salt the molecular weight) and the amount of the substance contained are identical. In the case of bi-valent, tri-valent, etc., it is J or J of the atomic (or in the case of a salt the molecular) weight. For example : A normal solu- lution of HC1 contains 36-37 grammes HC1 in a litre. In the case of Hi SO 4 it would be ~ = 49 grammes H a SO 4 . Frac- tions of the normal, such as semi-normal, deci-normal, etc., are represented ?, ~, etc. In the fluid used with Lunge and Zeckendorf's apparatus deci-normal solution of anhydrous sodium carbonate is prepared, and coloured by dissolving in it I gramme of phenolphthalein. This keeps well in a properly closed bottle, whereas weaker solutions will not. For use this is made into Na a GO 3 as required, by taking 2 cc and diluting up to 100 with pure recently boiled distilled water free from CO 2 , 10 cc of this are then put in the bottle connected, as already described, with the rubber ball; this JL Na 4 CO 3 should be freshly prepared when required for use, as it will only keep for a short space of time. .WERSITY 122 D irectio ns fo r use. If the average quantity of carbonic acid in the air of a chamber is to be tested, the air must be well mixed before the sample is drawn ; if the air in one portion only is to be taken, the free end of the indiarubber ball must be placed in it, and the ball pressed several times by the hand in order to fill both ball and bottle with the air. The bottle is then opened, and 10 cc of the test solution introduced by means of a 10 cc pipette (but the pipette must not be blown into), the stopper of the bottle quickly replaced, and the bottle shaken rapidly for about a minute, the indiarubber ball is then slowly but firmly pressed together, so that the air streams through the fluid, and the bottle shaken as above, and this repeated until the red colour in the solution is discharged. From the number of times it is necessary to press the ball, the carbonic acid in the air is calculated by the table herewith ; if only a few pressures are necessary, the air of the space tested is very bad ; if from nine to ten pressures, moderately good ; if from twenty to twenty-five, very good ; in the open air forty to fifty pressures are required. If the proportion of carbonic acid is large, the discharge of colour is sharp and complete, in pure air the change is uncertain within two or three pressures, and a complete discharge is difficult to obtain. But in pure air three pressures only cause a difference in the third decimal point. Table. Number of Pressures of Indiarubber Ball. Parts per 1,000 of Carbonic Acid in the Air. Number of Pressures of Indiarubber Ball. Parts per 1,600 of Carbonic in the Air. 2 3'o 16 0.71 3 2'5 17 0-69 4 18 0-66 I 1-8 19 20 0-64 0'62 7 I -35 22 0-58 8 1 '*5 24 54 9 ro 26 0-51 10 0-9 28 0-49 ii 0-87 30 0-48 12 0-83 35 0-42 13 0-8 40 0-38 H 0-77 48 '3 '5 074 123 Angus Smith's method. Angus Smith estimates the CO 4 in the air, by taking a series of bottles varying in capacity from 20.63 ounce down to 2*5 ounce, and adds |-oz. of lime water to each, commencing with the largest until he reaches Fig. 350. LUNGE & ZECKENDORF'S APPARATUS turn LApcLiciii^ me anLiiicUMie Variety, is" '"burnt in cast-iron stoves ; red-hot cast-iron allows CO gas to escape through it by occlusion, whereas wrought-iron stoves are free from this objection. Carbonic oxide is known to escape through the joints in stoves, and in the case of cast-iron the carbon contained in it at high temperatures reduces carbon dioxide to monoxide. * In the Russian Navy, pyro-collodion powder is employed, which yields 54/54 volumes per cent, of CO as a result of the deflagration of pyro- collodion C 30 , H 88 , N 12 , O 49 = 30 CO + 19 H a O + 6 N a . 12 4 Another source of CO in the air, is when a gas-flame is used to heat water, as in some varieties of " water-heaters" the cold surface coming in contact with the gas interferes with combustion, and carbon monoxide enters the air. The escape of coal-gas is a frequent cause of CO poisoning, as it contains about 4 to 7 per cent, of carbon monoxide. " Water-gas " has on several occasions caused deaths from carbonic oxide, as recorded in Lancet for 28th December, i88g ; in this case water-gas, which consists of hydrogen and carbonic oxide, escaped into a room, and being odourless was unnoticed. If this gas is employed it should be odorised, in order that any escape may be speedily detected. The detection of carbon monoxide in air is a very simple matter if a spectroscope be available; the test, which is known as Vogel's, is conducted as follows : A sample of the suspected air is obtained in the ordinary manner already described, and to this is added a few drops of a very weak solution of blood, just showing a faint red colour ; after being w r ell shaken up it should be examined with the spectroscope ; two dark bands will be seen in the spectrum in the yellow and green parts of the solar spectrum between Fraunhofer's lines D and E. If these lines be due to oxy- haemoglobin, they will disappear on the addition of a drop or two of colourless ammonium sulphide solution, and in their place will appear one broad band, shaded off at the edges, intermediate between them. If the dark bands were due to carboxyhaemoglobin, no marked change is noticeable, showing" that carbonic oxide forms a stable compound with haemoglobin. The left absorption band of carboxyhaemoglobin, i.e., the one at the yellow end of the spectrum, lies more to the right than is the case with the oxy-haemoglobin. The test conducted with a drop or two of blood as above will, according to Vogel, detect even 0^25 per cent, of CO. If greater precision is required, a mouse in a wire cage is kept in the suspected atmosphere, and after a time drowned, divided in the region of the heart, and the blood examined as before ; 0*03 per cent, of CO, if present, can be shown by this method. As a control a similar experiment with a mouse kept in the open air may be performed. In the Analyst for September, 1897, page 249, Vol. XXII., a reaction of carbon monoxide, in which a weak solution of K 2 Mn a O 8 acidified with HNO :1 is decolourised by CO, is given ; if silver nitrate be added the reaction is more speedily obtained. M. Mermet described the test, and states that the 125 reagents must be used fresh, the air should be filtered through cotton wool and passed through absorptive reagents to remove dust or gases such as hydrogen sulphide, liable to decolourise the permanganate solution ; a control test with normal air may with advantage be performed. The reagents are prepared as follows : 2 to 3 grammes of crystalized silver nitrate are dissolved in a litre of water. The permanganate solution is prepared by boiling i litre of distilled water with a few drops of pure nitric acid, and destroying any organic matter present by adding a few drops of permanganate solution, when cold, I gramme of perman- ganate crystals and 50 cc of pure nitric acid are added, and the solution stored away from light and dust. The reagent is prepared, immediately before use, by mixing 20 cc of the silver nitrate solution with i cc of the permanganate solution, i cc of pure nitric acid, and 28 cc of distilled water freed from organic matter. To apply the test the reagent is poured into a flask con- taining the air under examination, and precautions against dust or reducing agents taken as indicated above.* Organic matter in air, the result of respiration and trans- piration, i.e., given off from the skin and lungs, is (a) nitro- genous; (b} oxidisable ; (c) organic; and (d) putrescent ; because (<*) it will yield ammonia; (b) it will reduce a solution of K 2 Mn a O , as shown by the bleaching effect; (c) it is charred by H 2 SO t , as shown by drawing air known to contain this animal organic matter through H a SO 4 , which renders it dark coloured ; (d) if air containing the organic matter be drawn through pure sterile distilled water it will putrefy and give off offensive smelling gases. Estimation of Organic Matter in Air. Organic matter in. the air can be estimated quantitatively by aspirating known quantities of air through doubly distilled 1 * Miners are often killed in colliery explosions by the "after-damp," a mixture of gases, amongst which CO is met with. The rescue party are subjected to the same risk of asphyxia from this ' after-damp " as those who were in the explosion. As a safeguard, Haldane has recommended that those forming the rescue party should take with them a cage containing mice, and cylinders of oxygen gas. Mice breathe much more rapidly than human beings, are much sooner affected with signs of CO poisoning, and the death of the mice would serve as a warning, and enable the rescuers to escape, since the candle will continue to burn brightly in air containing "after-damp," whereas with the "choke-damp" the CO, speedily extinguishes the light. Artificial respiration and inhalation of oxygen and fresh air, with the administration of stimulants and maintenance of bodily temperature, are, according to Dr. Clifford Allbutt, the chief points to which attention should be turned. 126 water, (a) And then we can estimate this by the Wanklyn process as detailed under water analysis ; or (b} determine the amount of oxidisable matter by the amount of oxygen absorbed by the Tidy-Forchammer process also described under water analysis ; or lastly (c) collect a sample of air, as in Pettenkofer's process, and add to this bottle so cc of N r 1000 K. 2 Mn a O 8 . - K 2 Mn 2 O 8 is made by taking 100 cc of ^ K 2 Mn 2 O 8 and adding to it 50 cc of i : 6. H o SO 4 and distilled water to make up to one litre. Since i cc of ** K 2 Mn 2 O 8 has o'oooS grammes or o - 8 milli- grammes of available oxygen each, i cc of has o - oo8 milligrammes of available oxygen. Shake up and leave for ten minutes, then take 25 cc of this K 2 Mn ft O 8 solution, make this up to 150 cc, and label it sample ; and also take 25 cc of the original unexposed 5 K 2 Mn a O 8 solution, make it up to 150 cc, label it standard. Place the two measures containing these solutions side by side, taking care that each one is of the same calibre, com- pare the colours, and from a burette run in sufficient ^ K. ] o o o * Mn 4 O 8 to equalise the colours, read off and note the amount which was required to match the sample with the standard, and the calculation is performed as follows : i litre of oxygen weighs 15*96 X 0*0896 = i '43 grammes, therefore i cc of O 2 = 0-00143 grammes, or in other words 1-43 milligrammes, so i'43 : '008 :: i : x which = 0^00559 cc, i.e., in round numbers ' Solids not fat ... 8-5 . ,, And these figures are the ones which we employ when calcu- lating the amount of fat abstracted or added water in samples of adulterated milk. For ordinary purposes it is sufficient to determine the total solids per cent, by weight; fat per cent, by weight; amount of ash per cent, by weight ; per centage of cream by volume; and specific gravity at 60 F., in addition to noting the reaction, physical character, and presence or absence of adulterants or preservatives. Specific gravity is taken after first carefully shaking the sample by means of a hydrometer, or if greater accuracy is required by a Westphal balance, the temperature must be noted, and if it is not 60 F. the specific gravity must be cor- rected for temperature by means of the table on next page. The total solids are determined by taking 5 cc of milk in a carefully weighed platinum dish, weighing the 5 cc before and after evaporating to dryness. For example : Platinum dish weighs 33.5 grammes ; platinum dish with 5 cc of milk weighs 38-66 grammes ; 38-66 33-5 = 5-16, which is the weight of the milk taken, after drying, weight is 34-145; 34-145 -- 33-5 = 0.645, which equals total solids in 5-16 grammes of milk ; "645 X 100 - = i2'5 per cent, total solids. 5-16 Ash. This is obtainable by incinerating the residue left after evaporation to dryness at as low a temperature as pos- sible until it is quite white, the ash is then calculated to per centage as before, e.g. 136 Ill p p P PO o s iO O O4 04 P P 04 oo ON 04 04 P P O PO p M 04 PO PO p p PO PO p (V) PO p o p M 04 PO 4 04 vb t^ N 04 do 04 ON O 04 PO PO O4 PO PO PO s PO PO b O O O4 PO 04 N o 4- O O 04 P !" do 04 M 04 ON O 04 PO 04 PO 04 PO 04 PO PO PO PO PO TJ- io vb PO PO 8 b 00 00 M 04 04 C"4 00 PO O4 4 ON O do 04 M ON O 04 PO PO 04 04 04 PO PO PO 04 PO 04 04 VO vO 8 04 04 PO 04 4 00 04 oo ON N 04 & o p 04 PO PO PO o O M io VO PO PO 8 to 8 vp vp 04 04 VO PO vp 4 04 S 1" 04 t^ 00 00 ON 04 04 op oo ON M 04 PO PO PO PO Z V 8 10 tO M 04 PO JO 4- iO vO vo o 04 N VO 04 vO vO 00 ON N O4 ft M 04 PO PO op PO PO OO 00 4 io! PO POJ VO PO b 04 M 04 04 N PO 04 ot N 04 04 tO JO CO ON N 04 ft vo vO M 04 ^ PO vO PO PO O vO pn PO J $ O4 8 PO PO 04 C4 PO 4 04 PO PO io vb 04 04 04 CO ON 04 N b PO Tf IO i-< 04 PO PO tO PO PO vo vn 4- io PO PO ^_^ VO b 04 O4 >-> 04 N PO 04 4- 04 io VO PO N PO PO PO b PO PO PO M 04 PO PO PO PO PO PO PO 1 PO P<"> 1 b 04 M 04 PO O4 4 04 io O 04 04 N 00 ON 04 04 PO M 04 PO PO PO PO PO <^ i ^ O N M N O4 N P ? PO p CI p VO VO 04 04 P P s 00 ON SO4 o M 04 PO PO p p PO PO p f VO ? ? H S *< 1 ON ON M 04 0? Tf io 04 04 1 1 0? b M PO PO 04 'O PO 4 o 8 - 1 ON O\ 8M 04 CO O4 04 op PO op op op oo oo l>v OO N 04 oo ON 04 oo t> b i-i PO CO 04 PO R ^ 6C I s * 4) 10 Q 00 ON oo oo 8H N 00 04 vS PO N 04 04 o 04 t^ OO N 01 04 b PO PO vO 04 PO vp vp M b w 04 04 o7 PO 04 vp vp O vb 04 vO vO t>. do N N VO 04 iO to PO PO VO 04 PO IO to PO 4 PO PO o to VO bv M 8 5 vp 04 VO PO 04 vO to o 04 to to I s * do 04 04 rf ON 04 PO PO 04 PO PO PO PO V PO PO >o to M b -i 04 N s PO 4 io 04 N vb 04 r^ oo 04 OJ ON 04 . ft PO 04 PO PO 4 PO PO a Tf M O w PO Tf VTJ O4 04 vb 04 K do 04 N | PO PO PO R S N 2 8 8 4 PO 04 4 VO 04 M 3 t^ 00 04 04 S? b M PO PO 04 PO ro PO PO PO tO PO 8 5 PO PO PO 0< O4 ot o? 04 4>* 00 04 04 04 o o b M PO PO PO ON 00 04 PO PO PO tO 2 b M 04 04 VN 1 ot o? i t^ 00 04 04 04 ON O 04 PO M PO 04 PO PO PO ill o 8 i PO N O Tj- p iO O p ? 04 P P O p M 04 PO PO O PO PO Tf IO PO PO j3 a, - Platinum dish and ash weighs 33^538 grammes; 33*538 33'5 = 0-038 ; 0-038 x TOO - = 0-736 5-16 It is important to note the amonnt of ash ; as a rule this varies from about 0*73 to 0-75 per cent. If there be excess of ash add to it some dilute HG, effervescence indicates the addition of a carbonate, and probably this was sodium bicar- bonate added to neutralise acidity in milk slightly turned. Or if the ash be excessive evaporate some more milk to dryness and test for boric acid as detailed subsequently. Fig. 37. LEFFMANN-BEAM APPARATUS. Fat. The most convenient method of estimating fat is that known as the " Leffmann-Beam " process, of which there are several modifications, depending for their action on the running together of fat globules which occurs when an acid such as hydrochloric acid and fusel oil are added to milk ; fusel oil is an essential, as it is found that without it the milk globules do not as readily coalesce. The fat globules set free are brought to the surface by means of a centrifugal apparatus. The Leffmann-Beam apparatus consists of a vertical rod connected to a series of highly geared .wheels, giving a large number of revolntions per minute. The upright rod supports a horizontal one, at either end of which are four metal carriers which hang vertically when the apparatus is still, but are horizontal when revolving rapidly ; in each of these fits a small graduated bottle which holds the milk and re-agents. The process is conducted as follows : Take 15 cc of milk from a sample which has been well mixed, pour this out into a Nessler glass and add 3 cc of a mixture of equal parts of fusel oil and strong hydrochloric acid, mix well, next add slowly drop by drop 9 cc of strong sulphuric acid, mixing the acid and milk together carefully so that when all the acid has been added there are no undissolved masses of curd remaining; next pour out this mixture of (i) milk, (2) hydrochloric acid and fusel oil, and (3) sulphuric acid into one of the bottles supplied with the apparatus, add to this mixture in the little graduated bottle some 50 per cent, sulphuric acid sufficient to fill up to the on the scale, if freshly mixed it will always be hot enough, but if made some time before it will be necessary to warm the sulphuric acid and water, and before pouring it into the small graduated bottle it is well to pour a little of this 50 per cent, acid into the tube in which the milk was mixed with the reagents in order to rinse out any of the mixture which might have been left behind. Before commencing to whirl the milk, care must be taken to see that three other carriers are equally weighted w r ith similar bottles filled, if necessary, with sulphuric acid and water, as a rule the bottles from previous analyses will be available to act as counterpoises. Next cause the bottles to revolve smartly by turning the handle moderately quick, then after two minutes, or if dealing with poor milk three minutes, the machine is stopped and the sample examined, w r hen the fat as a clear layer of oil will be found floating on a dark brown clear fluid, the number of degrees over which the fat extends tells us the per centage of fat, each ten divisions indicating i percent, of fat ; for example, after whirling the milk for two minutes the fat was found to occupy 34 divisions, there is therefore 3-4 per cent, of fat. If we have estimated the fat by this apparatus (or any other method), and have also determined the true specific gravity at 60 F, we can determine the amount of total solids by means of Richmond's slide rule (Fig. 38} . This consists of a rule 12 inches long on which three scales are marked. On the top is the fat, in which every 1*167 inc ^ }S divided into tenths. The sliding part has an arrow marked on its upper margin carrying the various specific gravities, each division being 0*25 inch in length ; the total solids are marked on the lowest scale, each division is i inch long divided into tenths and 139 indicating total solids from 17 to 5, and when a reading is made, if any two of the three items, fat, specific gravity, or solids are known we can find the third. For example if the fat be known, set the arrow on the sliding scale against the amount of fat indicated on the top corresponding with what is known to be present, then observe where the specific gravity ascertained, corresponds with a line on the lowest row of divisions indicating solids ; or again, suppose the solids and specific gravities are known, set the specific gravities to correspond with the known total solids, and the arrow will now mark the percentage of fat. It will be seen that given any two of the three items, specific gravity, percentage of fat, or solids, we can find the third. In practice specific gravity and fat are always determined, and the total solids can be found by slide rule, but it is well to determine the total solids by actual experiment, as this affords a check to other results, having found the solids experimentally, the fat found by analysis should correspond with that shown by slide rule, or having found the fat experimentally the solids, by slide rule, should correspond approximately with those shown by rule, the rule is made according to the formula, M. N. Gerber, in L' Industrie Laittire, No. 50, p. 397 ; No. 52, p. 413, 1892, and No. i, p. i ; No. 6, p. 43, 1893, estimates the fat in milk by a centrifugal apparatus of his own design, he uses amyl-alcohol as in the Leffmann-Beam method, and the process, with certain modifications, can be employed for estimating the fat in milk, butter and cheese. For milk, 10 cc milk are measured into the bottle and i cc of amyl-alcohol is added, and then 10 cc of strong sulphuric acid (1-820 to 1*825 specific gravity), the bottle is closed with a caoutchouc stopper, and the contents well shaken and then centrifrugalized for two to three minutes, and the percen- tage of fat read off when the whirling is complete. 140 The original Gerber apparatus was worked by handle, but the new model, which runs in ball-bearings, is so con- structed that by giving from 15 to 20 sharp pulls with a string as in spinning a humming top, the apparatus is made to rotate at the rate of 2,000 revolutions per minute, and once started will run for about three minutes, at the end of which time the fat will have been completely separated out. The Werner-Schmidt method for the estimation of tat consists in taking a known quantity of milk, separating the fat by addition of HC1, dissolving the separated fat with ether, taking an aliquot part of the etherial solution, then driving off the ether and lastly weighing the residual fat and cal- culating to percentage. A modification of the original process was described in the Analyst for April, 1867, by Mr. R. \V. Woosnam, who has devised a special apparatus as figured, which consists of two parts, who describes it thus : (a) A boiling flask with top, the mouth ground to fit the top of (b): (b) A graduated 100 cc burette with small tap at the side r placed preferably at about the 50 cc mark. To make a determination, pipette 25 cc of milk into the boiling flask (0), and about 28 cc (roughly) of strong hydro- chloric acid are added. For this purpose a 25 cc pipette, with stem sufficiently small to pass through the tap, is recom- mended. The 'flask is then placed in boiling water, and agitated frequently until the contents assume a pale brown colour. This generally occurs in about two minutes, and it is important that the action should not be allowed to proceed too far, or the sugar caramelized will be to some extent extracted by the squeous ether at the next stage. The flask is now cooled, and 50 cc ether added. The tap with which the flask is fitted is then closed, and the whole shaken vigorously for some moments, after which it is firmly fixed into the top of the burette (b), the ground surface making a tight joint. After the separation of the ether layer, the tap is turned on and the liquids allowed to flow gently into the burette. The measurement of the ether layer is next read off, and, after adjusting the levels of the liquids by manipulating the two taps of the burette, an aliquot part of the ether layer is drawn off from the side tap into a suitable weighed vessel, the ether driven off, and the fat weighed in the usual manner and calculated to percentage. For example, 10 cc of milk were treated as detailed, and all the fat was dissolved in say 28 cc of ether, 20 cc of this are pipetted off, 8 cc are seen to remain, on drawing off the ether in a tared dish the fat which remains weighs 26 grammes. All the fat in 28 cc of ether .". = 20 : 28 : : -26 : x = 0^364, but 28 cc of ether contains the fat of 10 cc milk, so 28 cc X 10 contains the fat of 100 cc milk which 2'64, expressed more concisely the calculation in this example would be 28 x '26 x 10 28 x -26 = 3-64 p.c. fat. 20 2 The Adams' method for the estimation of fat is the official method of the Society of Public Analysts. It consists of taking two strips of specially prepared, fat-free, bibulous paper, and dropping evenly over the whole extent of each piece 5 cc of milk, this is dried in the air, and then, to ensure all the water being removed, it is dried for a few minutes in the water oven, the object of the complete drying of the milk is to prevent substances other than fat being taken up by the ether in the next stage, in which the dried paper containing the fat is wound round a piece of glass rod, so as to make it into a neat coil, after which the glass rod is removed and the coil placed in the chamber of a Soxhlet extractor, after which a small weighed flask is attached to the lower part of the apparatus by means of a perfectly fitting perforated rubber stopper, the flask should be about two-thirds full of ether, i.e. containing sufficient to fill the chamber containing the paper about one-and-a-half times, the upper part of the extractor is fitted to a condensing apparatus, and the flask containing the ether has a basin of water placed beneath it, and below this basin of water is the lamp ; great care must be taken to avoid all possibility of a flame coming near the ether containing flask. Very soon the ether will boil, and, by means of the arrangement of tubes, the ether vapour will be conveyed into the condenser whence it will distill into the chamber containing the paper, which it will gradually fill, when filled, the ether siphons over into the small flask, and this filling and siphoning of the extractor must be allowed to proceed about twelve times, then when it is nearly all siphoned over, the lamp is removed, the paper taken out, and the other coil containing the other 50: of milk inserted in its place ; the same process is repeated as before, and when the ether has all been siphoned over for the last time, the coil is removed, the ether in the flask driven off, and the fat which remains is dried and weighed, the amount calculated to percentage on the weight of milk taken. The weight of 10 cc of the milk is determined by pipetting 10 cc into a tared platinum dish and weighing. 10 cc weigh say 1 0-3 grammes, and the fat found weighs say 0*4 grammes, then 100 x 0-4 40 - = - - = 3-88 per cent. 10.3 10-3 142 The amount of sugar in milk need not as a rule be deter- mined, but if it be necessary, take 5 grammes of the milk, and dilute to 100 cc with ammonia and water, pour this mixture into a burette the nozzle of which passes through an opening in the cork closing a Pavy's flask, and add it drop by drop to 50 cc Pavy's solution which is kept boiling in a Pavy's flask, the ammonia which is driven off must be led away into a fume chamber. The process is stopped the moment that the blue colour is just discharged, and the amount of diluted milk which has been run in is noted, and the result calculated as follows 100 cc of Pavy's solution = 0-05 grammes of glucose, C fi H 12 O. + HO = 0-0678 grammes of lactose, or lactobiose, C H i2 0,, + H I tor example 5 grammes of milk made up to 100 cc with 50 per cent, ammonia solution were placed in a graduated burette and added to 50 cc Pavy's solution as detailed 13-89 cc of the 5 per cent, solution of milk = 50 cc Pavy's soln. 2778 cc ,, ,, ,, ioo cc ,, loocc of Pavy's solution contains 0^0678 grammes lactose 27-78 cc of 5 per cent, milk = -0678 grammes lactose, 27-78 and amount of pure milk = -0678 grammes of lactose 20 1-389 grammes of milk contains '0678 grammes of Ia6lose ioo x -0678 =. per cent. Ia6lose = 4-88 per cent, lactose 1-389 In an analysis of milk, the essential points are the per- centage amounts of fat, total solids and specific gravity. The Society of Public Analysts erring on the side of leniency in laying down a standard of milk, have declared that the percentage of fat to solids not fat, is as 3-0 to 8-5, though 3-84 fat, and 8*82 of solids would be more accurate, suppose that a sample of milk shows 3*0 per cent, fat, and 9 per cent, of solids not fat, it is evident that a certain percentage of fat has been removed, or solids other than fat have been added to the extent of ro per cent., assuming that the analysis shows that there is nothing abnormal in the solids, then to ascertain the extent to which fat has been removed, we proceed thus 3' - x ascertained amount of solids not fat, gives the 8 '5 amount of fat which should be present, then if this amount is more than the amount of fat actually present, the calculation is as follows 143 Let s. n. f. solids not fat and a. f. = fat found in sample 3' then - - x s. n. f. = tat which should be present; call this F r then 100 x (F - a. f.) -*- F = the percentage amount of fat originally present which has been abstracted, e.g., in the cast- quoted above, where the solids not fat were 9^0 per cent, and the fat was ascertained to be present to the extent of 3 per cent. 3-0 x 9 27 then = = 3-17 and 100 x (3*17 3*0; -f- 3-17 = 8'5 8'5 (ipo x 0-17) -f- 3-17 = 5-36 the percentage amount of fat originally present which has been removed. We can also assert that at least n per cent, of water has been added to the sample if the solids not fat are less than 8'5 per cent. By calculating as follows, let s. n. f. = ascertained amount of solids not fat present in bhe sample, then if 8-5 per s. n. f. x 100 cent, represent 100 per cent, normal milk, then - 8'5 (s. n. f. x 100) = percentage of normal milk present, and 100 8-5 = percentage of added water. Example. Solids not fat in a sample are 7-93, 7-93 x 100 793 then - - = which = 93^29 per cent, of pure milk, or 100 93*29 = 6-7 per cent, of added water, or more directly (8-5 s. n. f. as follows, x 100) which gives the percentage of 8-5 added water direct in the example just given, thus (8'5 7'93 x IQ o)_ '57 * TOO ^57 8O. _ Q. r< 5 5 " 5 H. Droop Richmond has recently pointed out* that much more accurate results are obtainable if we calculate the per- centage of added water from trfe last two figures of the specific- gravity of the milk taken at 60 F (water being 1,000), by adding these figures to the percentage of fat found to be present, we obtain a constant. The average of a long series of analyses of milk samples, known to be genuine, which have been made by different analysts shows this constant to be P. 169, Analyst, Vol. XXIII, 1898. 144 36'02, or in round numbers 36*0 ; now if the calculation is being made for the law courts, in order to give the defendant the greatest latitude which can reasonably be allowed, the constant, resulting from the sum of G-f- F is assumed to be 34*5, just as when the amount of added water is being calcu- lated from the amount of solids not fat, which are present, the limit of solids, not fat, in natural milk is assumed to be 8-5 instead of 9 - o per cent., which would be nearer the true amount. Let 36= 100 per cent, milk, then 36 n x i oo - percentage of added water ; 36 where n = number resulting from the sum of the ascertained specific gravity and fat in the sample in question. Richmond made a long series of.experiments, by adding a known amount of water to the milk, and then calculating the added water by the two different methods detailed above, and in 13 different experiments, of which he gives the results, it is shown that by making the calculation of added water from the sum of specific gravity and fat, in 12 cases he was nearer the truth, the average error of the series being I'oi per cent, under the true amount, whereas by the other method the average error was 2*16 per cent, under the true amount. It is not often necessary to estimate the proteids con- tained in a sample of milk,* but if it is required to do so, the nitrogen contained is determined by Kjeldahl's process, and from this the proteids are calculated by multiplying by the factor 6'33 ; 6*25 has been suggested as giving more accurate results, but 6*33 is the factor usually employed. For Kjeldahl's process we require (i) a strong hard-glass flask, which is fitted with a perforated rubber cork which can be connected with a distilling apparatus, (2) a flask to a6l as a receiver, (3) a burette for use in titrating the acid, and the following solutions : NT Sulphuric acid or ^ Oxalic acid and ^J Sodium hydrate solution Solution of methyl-orange as an indicator. Some strong sulphuric acid, known to be free from ammonia. Strong solu- tion of sodium hydrate, from which all traces of ammonia have been removed by boiling : Detail : Weigh out 5 * In legal cases in order to prove abstradtion of cream, or addition of water, it is necessary to make a full analysis, several cases in which the addition of water was beyond a doubt, have been dismissed because the analyst had negledled to state the constituent parts of the sample analysed. grammes of milk, (this is preferable to taking 5 cc and making the necessary allowance for the weight of 5 cc of milk being more than 5 grammes.) Evaporate the milk to dryness in the hard-glass flask already mentioned. Add 10 cc of the strong sulphuric acid, and -75 grammes of red mercuric oxide, fix the flask in a slanting position over a bunsen burner, in a fume chamber, the flame being regulated so that the temperature of the acid is just below fts boiling point. If it tends to become clear nothing more is added, but if after a time it is still black 5 to ip grammes of potassium sulphate are added, and the heating is continued for from one to two hours, after which cool, and add about 200 cc of distilled water and pour into distilling flask, rinse out with more distilled water, then add carefully an excess of sodium hydrate solution until the acid is more than neutralised, connect the flask with the distilling apparatus, and -commence distilling, and allow dis- tillate to be collected in a receiver containing 40 cc of T ^ oxalic KJELDAHL'S APPARATUS. or sulphuric acid. When the greater part of the contents of the flask have distilled over, the process is stopped and the contents of the receiver are titrated with ** sodium hydrate, the exact strength of which has been accurately determined by titration with T ^ acid, each i cc of the .J* acid placed in the receiver, which has been neutralised by the distillate =o - ooi4 gramme of nitrogen ; and the percentage of nitrogen is cal- culated in the manner shown by the following example : 5 grammes of milk treated by Kjeldahl's process, neutralised 20 cc of ^ acid, there are, therefore, 20 x 0-0014 gramme of nitrogen in 5 grammes of milk. 20 x -0014 - grammes nitrogen in I gramme of milk, 146 2O X 'OOI4 X IOO grammes nitrogen in 100 grammes milk : this worked out is found to be 0^56 per cent, nitrogen. Nitrogen multiplied by factor 6-33 proteids. 0-56 x 6-33 = 3-5448 per cent, proteids. Diseases spread by Milk. Disease may be conveyed through the medium of milk in two ways. 1. The secretion may be contaminated by an infected animal. 2. The milk may become infected after milking, by the addition of infected water, by washing the milk-containing vessels with infected water, or by contact with infected material or people. Class I. includes tuberculosis, foot and mouth disease, anthrax, acute enteritis. Class II. Typhoid fever, diphtheria, scarlet fever, cholera, diarrhoea. Class I. Tuberculosis is, without doubt, conveyed from animals to man by the use of raw r milk from tuberculous cows. * Tuberculosis is very common amongst stall-fed milch cows, especially when they suffer from over lactationt, that is to say they suffer from being drained of milk over periods far too prolonged ; other causes are, too frequent calving, and being kept in crowded ill-ventilated cow-sheds, where oppor- tunities are not wanting for the spread of the disease from one animal to another. . A very large number of milk samples have been found to contain the tubercle bacillus, but it is chiefly in those cows where there is tuberculous disease of the udder that one finds the bacillus. According to some, it is not essential for the udder to be affected in order to find it, but Dr. Martin says he never found the tubercle bacillus in milk, ._ even when tuberculosis in the cow was extremely advanced, unless there was tuberculous disease of the udder. The surest mode of detecting tubercle bacilli is to inject the suspected milk into animals, but this means of detection is available for only a few, and reliance must be placed upon microscopical * Sir Richard Thorne Thome has said "the greatest danger which man incurs of receiving the tubercular infection lies in the use of milk from tuberculous cows. f According to Nocard, tuberculosis is rare in Paris, because cows are not allowed to be kept for more than a year before they are fattened for slaughter. B.M.J., i3th August, 1898, p. 410. 147 examination of the milk. For example if we (i) allow the milk to stand for 24 hours, the sediment can be examined by making cover-glass preparations, and staining with warm Ziehl's carbol-fuchsin for from two to rive minutes, decolorising with 33 per cent, nitric acid, washing in water, and counter- staining with LofTler's methylene-blue, washing once more in water, drying, and mounting in xylol balsam, or (2) we may centrifugalise some of the milk, and examine the deposit as before, or (3) take about 200 cc of milk, curdle it by adding a little powdered citric acid, filter, and dissolve the precipitate collected on the filter in a solution of sodium phosphate, place the liquid thus obtained in a large test tube, add a little ether, shake for about ten minutes, decant the ether which contains the fat in solution, and centrifugalise the watery liquid and examine the deposit. (4.) In Practical Bacteriology by Kanthack and Drysdale, Van Ketel's method is recommended. This consists in adding 10 cc of liquefied carbolic acid to 200 cc of the suspected milk, shaking the mixture vigorously for two to five minutes, then setting aside in a conical urine glass (protected from dus.t with a glass cover) for 24 hours, at the end of which a little of the sediment is removed from the deepest layer with a fine capillary pipette and films prepared by rubbing a drop between two cover glasses in the ordinary manner, after which the films are dried in the air and passed three times through the flame, stained by the Ziehl-Neelsen method as already detailed and examined with i/i2in. o. i. lens. Lastly, if possible, inject a few cc of the milk collected under aseptic conditions, into the peritoneal cavity of a guinea- pig, tuberculosis results if the tubercle bacillus is present. In order to avoid the risk of contracting tuberculosis through the agency of milk, all milk should be sterilised or boiled. If milk be kept at a temperature of 65 C (145 F) for 30 minutes, heated to 80 C (176 F) for five minutes, or boiled for one minute, the tubercle bacillus will be destroyed. The majority of people dislike the taste of boiled milk, in which case the milk should be kept at 65 C for 30 minutes, as in that case the taste will not be appreciably altered, if the temperature does not exceed 70 C (158 F)/ The question as to whether sterilised milk is suitable as an article of diet for infants has been investigated by Mr. J. K. Barton,* who divides sterilised milk into two classes, (I) com- pletely, and (II) comparatively or temporarily sterilized milk. (I) without fresh food will eventually produce scurvy. If the * B.M.J. and January, 1897. Page 14. 148 milk be over-heated or the heating be too prolonged, changes occur in the lactalbumin, by which its solubility is lessened, the fat globules also undergo a change, they tend to coalesce with each other, and with some of the insoluble albuminous matter. (II) never produces scurvy, and if the sterilization has been effected by raising the temperature of the milk to the boiling point, or within two degrees of boiling point, and kept at this temperature for from 5 to 15 minutes, is practically safe from pathogenic organisms. Sterile milk, after exposure to air, turns as quickly if not more quickly than ordinary fresh milk. Sterile milk should be kept after sterilization at a uniform temperature of 40 F (4'45C) in many cases of bottled'" sterilised" milk which has been kept at the ordinary temperature of a room, the process of sterilization has been proved incomplete, it has sufficed to destroy, or is capable of destroying such pathogenic organisms as the bacilli of cholera, typhoid fever, or tuberculosis, but has failed to destroy the bacilli of infantile diarrhoea, a disease which is accountable for so much infantile mortality " these multiply at a comparatively high temperature, hence infantile mortality from diarrhoea is higher in the summer."* Flugge has even gone so far as to say that the sterilized milks of commerce are dangerous preparations, and that their sale ought to be stopped by the public authorities. Foot and mouth disease has been already alluded to in Part I. p. 35, and Siegelt has described a small epidemic of foot and mouth disease clearly attributable to milk, the first case was one with symptoms of stomatitis aphthosa, the inside of the lips and tongue were ulcerated, and there was a pale rash on the body, in other cases the symptoms were stomatitis and enteritis, whilst many suffered from discharge from the ear, swelling and ulceration of the gums and loose- ness of the teeth, and great exhaustion. In one family where the father, and tour children aged from ij to 10 years, were attacked the symptoms were inflammation of the mouth, and in two cases blisters on the fingers and toes, one child showed a rash resembling measles and died from exhaustion, alto- gether there were fifteen cases, and it was proved that the milk had been derived originally from a farm where foot and mouth disease had broken out ; the fifteenth case was of especial interest, as it occurred in a man who lived in a village where there were no cases of foot and mouth disease, but it seemed that this man had attended a fire in the village where the suspected dairy was, and had drunk milk there. i 'Analyst, page 102, Vol. XXI. 1896. f Journal of State Medicine, Vol. VI., page 178. 149 In these cases the milk which had given rise to the outbreak was noticed to have possessed a yellowish colour and peculiar smell. The Hendon disease. The outbreak of scarlet fever* which occurred in Marylebone in December, 1885, was undoubtedly traced to milk, but whether the milk owed its power of infection to the cows from which it was obtained, or whether it was infected by a person suffering from a mild attack of scarlet fever, is by no means certain ; the evidence would seem to point strongly to the scarlet fever being of bovine origin, but that there may have been a mild and easily overlooked case of scarlet fever amongst one of the farm hands is held by many. The history of the epidemic is this : An outbreak of scarlet fever suddenly occurred in South Marylebone, this was reported to the Local Government Board on i8th Dec., 1885, by Mr. A. Wynter Blyth, M.O.H., South Marylebone, and was traced by him to milk supplied by a certain dairy in South Marylebone which was in turn supplied by a dairy farm at Hendon, which also supplied milk to St. Pancras, Hampstead, Hendon, and St. John's Wood, each of which places became a centre of infection, St. John's Wood being the last for reasons which will be afterwards explained. Mr. Blyth ascertained in regard to the South Marylebone milk business that it was only amongst the customers supplied with Hendon milk, and Hendon milk alone, that scarlatina had occurred. On December I5th, when the customers in South Marylebone stopped purchasing milk from the suspected dairy, 63 gallons of milk were returned to Hendon, and con- trary to the farmer's orders were by the cowmen distributed amongst the poor of that place instead of being given to the pigs as ordered, and this was followed by an outbreak of scarlatina there. Dr. Power had in 1882 traced an epidemic of scarlet fever which occurred in the parishes of St. Gile's and St. Pancras to the milk supplied from a Surrey farm, where one of the cows had been suffering from an ailment, one of the symptoms of which was the presence of bald patches, in this epidemic no possibility of the milk having become infected from a human case was found by him; when therefore in the Hendon outbreak it was found that three newly-calved cows had been recently imported from Derbyshire! which were suffering from a vesicular disease of Vide Local Government Board Reports, 1885, 1886. f The dealer who was believed to have purchased these cows, in Derby Market, and who sold them to the Hendon farmer, resolutely refused all information whatever. the teats, and that in all the places where milk from these cows was sent scarlet fever occurred, circumstantial evidence was very strongly in favour of a bovine origin; later on it was discovered that although St. John's Wood had been sup- plied all along from Hendon dairy, the milk was from a shed in which there w r as no cases of this affection of the teats, but before long this disease appeared also amongst these cows, after which in due course scarlet-fever broke out in St. John's Wood, here then would seem indisputable evidence in favour of the disease being of bovine origin, and when it was after- wards found that by isolating the infefted cows, and only issuing milk from healthy cows, that the cases of scarlet- fever ceased to appear, Power and Klein, who were now working together, considered their case as proved. Crookshank and several others, by order of the Board of Agri- culture, investigated the matter, and came to the conclusion that the disease, from which the Hendon cows were suffering, was no other than cow-pox. In Wiltshire, Crookshank inves- tigated an epidemic said to be similar to the Hendon outbreak, and made cultures on nutrient gelatine and on agar-agar, and found the ordinary pyogenic organisms ; they inoculated calves, which were afterwards found to show the post-mortem appear- ances as in the Power and Klein's cases viz. : congestion of the lungs and pleural adhesions, microscopic examination of the kidneys showed glomerulo-nephritis, with infiltration of the sheath of the cortical arterioles with round cells and there were haemorrhages. In the Wiltshire epidemic, according to Crookshank, the conditions were exactly parallel to the Hendon outbreak, excepting that " in spite of the contamina- tion of the milk, no cases of scarlatina were found either on the farms or in the village, and there was no epidemic in the town in which the milk was distributed. * Sir George Buchanan, summing up Dr. Klein's investigations in regard to the Hendon disease, says that these showed " that subcultures made from human scarlatina, and inoculated into recently calved cows, can produce in those cows, along with other mani- festations of the Hendon disease, the characteristic ulcers on the teats, ulcers identical in character with those obtained at the Hendon Farm, also " that subcultures, either from the human or the cow disease, have an identical property of producing in various rodents, a disease similar in its patho- logical manifestations to the Hendon disease of cows, and to scarlatina in the human subject." These fa6ls with other evidence detailed in Local Govern- ment Board Report 1887-88 " go to form a mass of evidence * Bacteriology and Infective Diseases, p. 274. 4th Edition, Edgar M Crookshank, M.B. to show that the Hendon disease is a form, occurring in the cow, of the very disease that we call scarlatina when it occurs in the human subject." It is quite possible, and would seem highly probable, that the disease of the teats in Wiltshire cows, referred to by Crookshank, although in many respects resembling the affec- tion met with in the Hendon disease, was different and caused by one of the many streptococci which have been identified as distinft species. Sheep (excepting Algerian sheep) and cattle are very susceptible to anthrax, and the milk of an animal would soon show anthrax bacilli after contracting the disease, (Chamber- land and Straus) but since the disease is so rapidly fatal, and one which is recognised at once, it is a danger in milk which may be disregarded. The bacilli in anthrax appear in the blood of an affe6ted animal in about 15 hours, and would there- fore appear in the milk almost at the same time, through ruptured capillaries. The milk from cows suffering from acute enteritis has been known to give rise to a similar disease in human beings. Class II. Typhoid fever has been frequently shown as a milk-borne as well as a water-borne disease. In most cases where the disease has been conveyed by milk, it has been traced to washing the utensils with, or diluting the milk with typhoid infected water. The question as to whether cows, drinking typhoid infect- ed water, yield infe6led milk, has been raised. Likewise the danger of employing milk from cows fed on sewage farms, has been discussed as in the recent case at Aldershot, where, after a most careful investigation the milk was pronounced to be quite wholesome. Diphtheria has been frequently traced to milk infected by persons suffering from the disease, and there is no doubt that many people suffer from mild attacks of diphtheria which are so mild that they are overlooked, but which are yet capable of giving rise to severe cases of diphtheria, attended with fatal consequences. There is a bovine disease known as "garget," in which the udder is inflamed, this has been thought to give rise to diphtheria in the human subject, but it has never been conclusively proved, although there is no doubt but that cases have occurred of severe sore-throat in consequence of milk, in which the only source of infe6lion discoverable, was an affection of the udders of the cows from which the milk was supplied. Scarlet fever is readily transmitted through the medium of milk. 152 Cholera has been traced to milk, which had been diluted with water from a cholera infecled tank. Diarrhoea of infants is well known to be very frequently spread by milk, and the danger of so-called sterilized milks has already been commented on. Preservatives in milk : Those most frequently met with in milk are formalin, borax and boric acid, Salicylic acid was at one time employed, but is now almost, if not quite unknown as a milk preservative, at any rate in England. Salicylic acid checks the action of enzymes, especially those that act upon starch. The detection of formalin is not difficult, and for weak solutions, such as are employed in the preservation of milk, the most reliable is the test first described by Otto Hehner, which consists in diluting the milk with water in a test tube, and running strong sulphuric acid down the side of the tube, taking care to prevent mixing, so that the diluted milk floats on the acid, if formalin be present a violet ring is seen, which increases on gently shaking the tube. Another test where there is doubt as to the presence of formalin, is as follows : Take about loocc of the milk distill, collect the distillate, and add to it a drop of weak watery solution of phenol, after which on the addition of strong sul- phuric acid, a bright red colour is seen. There is a test with ammonia silver nitrate solution, which gives a dark brown or black colour after standing in the dark for some 1 8 to 24 hours in contact with the distillate of 100 cc milk. 2 grains per gallon of 40 per cent, formic aldehyde is easily detected by this means, and a sample would, as a rule contain more than this, the usual amount of formalin is equal to 3*652 grains per gallon of 40 per cent. CH..O. This silver test is not often required, as the two first-mentioned tests are generally sufficient. Borax or Boric acid may be detected by evaporating the milk to dryness, incinerating and moistening the ash with a drop of strong sulphuric acid and a little rectified spirit or alcohol, on applying a light ; a green flame indicates boric acid. Another test consists in evaporating the milk to dryness, incinerating as before, dissolving the ash in a little hydro- chloric acid, when, on dipping a piece of freshly prepared turmeric paper in the solution, a brown colour is seen if boric acid be present, which, on the addition of a drop of dilute sodium carbonate solution, turns the paper blue-black. Salicylic acid is best detected by adding to 200 cc of milk an equal bulk of water, heating the mixture to 60 C, and iccof acetic acid and an excess of mercuric nitrate, filtering, and to the filtrate adding some ether, after which, shake, allow theether to separate, decant off the etherial solution, and drive off the ether by evaporation over a water bath ; if salicylic acid be present, the dry residue will show a violet colour with ferric chloride. The question as to whether the use of preservatives is in- jurious or not has received a considerable amount of attention of late, with the result that great diversity of opinion has been expressed. The general opinion is that preservatives such as formalin or boric acid, if present to a small extent, are in no way harmful ; formalin, it is true, renders proteids more difficult of digestion, but on the other hand it is extremely fatal to micro-organisms even in minute amounts, which by their presence, or the presence of their products, would be very harmful. Boric acid is, according to some authorities, a cumulative drug, which gives rise to gastro-intestinal disturbance in the form of vomiting, diarrhoea, and haemorrhage, it acts as a de- pressant. Dr. McWeeney has pointed out the difficulty which the subjects of chronic kidney disease and children have in getting rid of boric acid and salicylic acids, so that if a sample contains say 0^05 per cent, of boric acid, a child taking say 2 pints'of milk in the 24 hours would have to eliminate 8*75 grains of the substance, and if the milk contained O'i percent, of boric acid, 17*5 grains of boric acid would have to be dealt with, now the dose of boric acid for an infant six months old should not exceed three-fifths of a grain. On the other hand, Henry Leffmann in the Journal of State Medicine, for July, 1899,* says that "boric acid, in doses up to 3 grammes per day, is practically without in- fluence upon proteid metabolism, and upon the general nutrition of the body, 1 ' and further on he says, that " both borax and boric acid are rapidly eliminated from the body through the urine, 24 to 36 hours being generally sufficient for their complete removal." Boric acid does not appear to interfere with either starch or proteid digestion, and boroglyceride appears to have but little interfering action. Although contracts are not arranged by the Medical Officer for the supply of milk, yet the terms which should be insisted * Digestive ferments, with especial reference to the effects of food preser- vatives. 154 upon, should be clearly understood when a contract is given to anyone for the supply of pure milk. r. The contractor should undertake to notify to the proper authority any cases of sickness amongst the herd supplying milk, and no milk shall be supplied from any cow that is sick, or which is being treated with medicines. 2. That any cases of sickness amongst the cows shall be notified to a duly qualified veterinary surgeon, cases of Tuber- culosis to be at once separated, and doubtful cases subjected to the Turberculin test. 3. That any changes in the herd, such as additions or removals of animals, be notified to the proper authority, and in no case is the milk of a newly-calved cow to be supplied, until it is free from colostrum, and does not curdle on being boiled. No milk to be supplied from a cow, which has not been at least 24 hours under the observation of the contractors. 4. That the cow-sheds be properly ventilated, and be sufficiently large to prevent overcrowding. The stalls for single animals to be not less than 8 ft. by 4ft. 6 ins., and for two animals 8ft. by yft., with an air space of at least 600 cubic feet per head, with efficient means to ensure ventilation. In measuring cubic space any height above i6ft. to be dis- regarded, and not taken into consideration in estimating, cubic space. 5. That the milkmen and attendants be free from disease, and cleanly in their habits and person. 6. That the milk when supplied, shall show not less than I2'o per cent, of total solids, 3-5 per cent, of which must be fat. 7. The milk must be supplied in properly cleansed churns, labelled with the date and hour of milking, the name of the farm, and be locked. 155 CHAPTER VIII. BUTTER. Butter, like milk, is not an article of naval dietary except in naval hospitals ; it is a palatable and easily digested form of fat, provided it be not rancid, when it gives rise to dyspepsia. A man doing ordinary work requires nearly three ounces of fat per diem, one ounce of which may with advantage be butter. Butter being comparatively costly, various substitutes have been devised, these are sold under the name of margar- ine. When there is no attempt at concealment, this is perfectly legitimate, since much of the margarine is a pure fat flavoured and prepared so as to resemble butter ; it is only when margarine is fraudulently supplied as butter, that exception is taken to it. Butter consists of the fat globules of milk which have been caused to coalesce by the process of churning, and containing, as the following table shows, a certain amount of water, curd and salt. The fat globules in milk are so intimately mixed up with a proteid known as caseinogen, that a complete separation is impossible. Good butter consists of : Fat ... ... from 80 to 88 per cent. Curd ... ... ,, 0-5 ., 3-0 ,, Salt ... ... ,, 1-5 ,, 5-0 Water ... ,, 8 ,, 14 ,, The fat is composed of fatty acids combined with glycer- ine, about 87 per cent of which are fatty acids, insoluble in hot water, consisting of about 40 per cent oleic and 47 per cent stearic acids, and about 6"j per cent are fatty acids soluble in hot water, consisting of butyric, caproic, and to a slight extent of caprylic acid. Oleic and stearic acids are not volatile when fresh, whereas, butyric and caproic acids are volatile. In other fats, the insoluble fatty acids are present to a much greater extent, and the soluble to a much smaller extent than in butter, thus constituting an important point in determining the genuineness of a sample of butter. The taste of butter is a means of discrimination by no means to be despised, and this requires no description. 56 The colour of butter varies with the season (which influences the food of the cows), and may vary between a pale straw when the cows are fed on hay, and a rich golden tint when grass is plentiful, but the colour is frequently more dependent on materials added in the process of manufacture than on natural causes. In towns, anatto, a harmless vege- table colouring material is perhaps the commonest; it is soluble in alcohol, which, on evaporation to dryness, turns blue when a drop of strong sulphuric acid is added to it. In the country, saffron or carrots often furnish the requisite colouring material when the colouring is artificial. Butter melts at between 86'g and 97 F., usually at about 89 or 90 F., and is readily soluble in ether, whereas, other fats are less soluble, and apt to throw down a deposit. The specific gravity taken at 100 F. varies between 0-910 and 0^914, that of water at 100 F. being rooo. In margarine and animal fats it is never above 0*904. Specific gravity is best taken by melting the butter at 100 F. and carefully filling and weighing a specific gravity bottle, filling implies an absence of air bubbles. Butter fat, when tested by the Hubl's iodine absorption test, is found to absorb much less iodine than foreign fats, it also yields a much greater amount of volatile fatty acids than any other animal fat. Curd consists of some portion of the non-fatty part of milk, chiefly casein together with lactose, lactic acid and a certain amount of fat. When butter is heated to about 150 F. over a water bath in a beaker, after a time the fat rises and leaves beneath it a cloudy layer of curd, salts and water. In good butter, the curd should be present in very small amount, 3 per cent or under ; in inferior butter this will be exceeded. The salt consists of some of the mineral matter contained in milk-plasma, but principally of sodium chloride, added to improve the flavour and assist the butter to keep. Fresh butter contains from 0*5 to 2 per cent, and salt butter may contain 6, 8, or even 10 per cent of sodium chloride. The amount of salt may be determined by washing a weighed portion of butter with pure distilled water and titrating the washings with standard silver nitrate solution, or the residue left after drying some of the butter at 105 F. may be burnt and the ash dissolved in distilled water and titrated with standard silver nitrate solution. Water is always present in butter, and is determined by taking 5 grammes of butter and drying in a tared platinum dish at 105 F. until the weight is constant, the loss of weight 157 gives the amount of moisture, this should not, as a rule, exceed 12 per cent. Water is added to increase the weight, but excess of water prevents the butter from keeping. Margarine is a term used to signify any fatty substance used as a substitute for butter, it is generally a mixture of the more-fluid portions of animal (beef or mutton) fat, with a certain amount of butter, or milk and butter added to give it a flavour of butter. Vegetable fats, such as palm and cocoa- nut oil are occasionally used, but as a rule, margarine consists chiefly of lard or fat taken from animals soon after slaughter, minced, washed and melted at a temperature not exceeding 112 F. and mixed with milk or butter as stated above. There are several ways of determining the amount of volatile fatty acids present in a sample of butter, the Reichert method of estimating the amount of pure butter present in a sample, depends for its action upon the fact already mentioned that volatile soluble fatty acids are present to a much greater extent in butter than in other animal fats; the process is as follows : Take some of the butter, melt it on a beaker over a water-bath, it will after a time be seen to separate into an upper stratum of clear butter-fat, below which is curd and water, if after a time the butter-fat does not become quite clear, it is filtered through a dry filter by means of a jacket funnel kept warm with hot water, or the filtering may be con- ducted in a water-oven kept at a sufficiently high temperature (100 F.), when the filtering is complete, 5 grammes of the clear liquid butter-fat are weighed into a tared narrow-necked flask of about 200 or 250 cc capacity, with a mark at 150 cc, to which are added 2 cc of 50 percent, sodium hydrate solution and 10 cc of alcohol having a specific gravity 0^803 at 20 C., i.e., 96 per cent, strength, the flask is next fitted with a rubber stopper through which passes a piece of narrow glass tube about 3 or 4 feet long, and the contents heated for 15 or 20 minutes on a water-bath with constant agitation, the fatty acids at the end of this stage are saponified, the rubber stopper and glass tube are removed and the alcohol driven off; when cool, 40 cc of 2'5 per cent, sulphuric acid are added, this de- composes the soap, setting free the fatty acids, distilled water is added to bring the whole up to the 150 cc mark, and the flask connected with a distilling apparatus after having pre- viously introduced a few fragments of recently ignited pipe- stem in order to prevent bumping ; the solution is gradually brought up to the boiling point and 100 cc distilled, tlie dis- tillate is filtered and titrated with ^ baryta-\vater, using phenolphthalein as an indicator. Mr. H. Droop Richmond, F.I.C., has kindly given me the detail for his own method of titrating the volatile acids. Fig 40 represents a burette for holding a standard solution of baryta, " the larger bottle is filled with the baryta solution, which is sucked over into the burette (before the tube from the top is put in position) ; the smaller bottle is filled loosely with sticks of caustic soda, or better with soda-lime. The only means by which air can enter the larger bottle is through the smaller one, in which it is deprived of carbonic acid, which would otherwise weaken the baryta solution, when the pinchcock on the tube con- necting the burette with the larger bottle is opened, the baryta siphons over and fills the burette to the required level ; the titration is performed by means of the pinchcock and jet at the bottom of the burette. The advantage of this apparatus is that all the air which finds access is freed from carbonic acid and there is only one opening to admit air." Fig. 40. RICHMOND'S BURETTE WITH CO 2 GUARD. A. von Asboth(C/iem. Zeit., 1897, xxi -> P- 2> 12 ) has described a process for the identification of genuine butter which isquoted in the Analyst by F.H.L.,* who is of opinion that in determin- ing the nature or amount of foreign fat which has been added to a sample of butter, Asboth's process, in conjunction with qualitative examination, is the most reliable test, it depends for its action on the fact that the lead salts of the soluble fatty acids are also soluble in water, whilst those of the insoluble acids are equally insoluble. Detail : ''Take 2-5 grammes of the sample and heat with 25 cc of \ alcoholic potash, the excess of alkali is titrated with acetic acid in order to deter- mine the saponification number. The residual liquid is then washed into a 300 cc stoppered cylinder containing 150 cc of * Analyst, Vol. XXII., p. 213, 1897. 159 water, 30 cc ot 10 per cent, solution of lead acetate, the whole is well shaken until the precipitate adheres together and the liquid has cleared. The precipitate is thrown on a filter of thick strong linen, and the cylinder and the precipitate washed with cold water. The lead salts of the insoluble acids are freed from moisture by squeezing them thoroughly, then removed from the cloth and put back into the cylinder, 200 cc of ether are added and the mixture shaken until the mass is -completely broken up. It is rinsed into a 250 cc oil burette, excess of i : 4 HC1 introduced and shaken until the ethereal layer becomes clear. The acid is then run off and the ether washed with water till neutral. The volume of the liquid is read, 50 cc are evaporated and dried to constant weight, and another 50 cc evaporated, dissolved in 50 cc alcohol and titrated with potash." ' Von Asboth's method for distinguishing between different fats is based on an attempt to identify each variety by the proportion of dleic acid it contains, 3 grammes of the sample are saponified in 50 cc of alcohol and I or 2 grammes of caustic potash. Phenolphthalein is added, and the solution neutralised with acetic acid. It is then treated with lead acetate as above and the insoluble lead soaps collected on the linen filter. The cylinder is drained from the water, the pre- cipitate and 150 cc of ether put in, shaken up and allowed to rest over night. A funnel and a thick filter-paper large enough to hold the solution and the washings are placed in the oil burette, moistened with ether, the contents of the cyl- inder thrown thereon and covered with a dial-glass. The insoluble matter is washed three times with ether using not more than 100 cc altogether in order to make certain that the whole of the lead oleate is dissolved. The filtrate in the burette is acidified with HC1, shaken up and washed as before. The total volume of the ethereal liquid is read off, 50 cc are evaporated in a beaker on the water-bath, taken up with alcohol and titrated with decinormal acid. The amount of alkali used, multiplied by 0*0282, gives the pleic acid in the ether, whence may be found the quantity existing in the fat examined, in this manner ten different samples of butter gave 3372 to 37-4 (mean 34); several margarine butters 45*48 to 46*0 ; oleo-margarine 42'6i ; bakers' fats 52*73 to 53*37; six lards 56-91 to 58-08; .one mutton tallow 25*44; four beef tallows 33.03 to 33*95 per cent, of oleic acid respectively ; it will be seen that the figures for each separate substance agree closely except in the case of butter itself (and here the vari- ation is not serious) ; and the values of all the other fats are very different, with the sole exception of beef tallow, which i6o however may be readily distinguised from genuine butter by its difference in consistency and melting-point." The amount of iodine which a sample of butter is capable of uniting with, is a valuable indication not only of the purity of the butter, but also of the nature of foreign fats and oils when present. Fats and oils are combinations of one or more fatty acids with glycerine, the fatty acids belong to two series (i) acetic and (2) oleic, possessing widely different affinities for iodine, and according to whether fatty acids of group i or group 2 prevail, so the amount of iodine with which the fat is capable of combining is smaller or greater. The test employed in this determination is that known as- Hubl's method of iodine absorption, in which a definite quantity of the fat under examination is placed in contact with an excess of iodine present in a solution of known strength, the solutions required are : 1. (#) A solution of iodine 25 grammes in 500 cc B.P. absolute alcohol. (3) A solution of mercuric chloride 30 grammes in 500 cc B.P. absolute alcohol. Solution ($) is added to solution (a) at least 12 hours before it is required for use. The mixture being known as " Hubl's reagent." 2. A volumetric solution of sodium thiosulphate contain- ing 24-644 grammes of Na 2 S a O 3 5 H ? O per litre. This is made by first making a ''rough" solution of sodium thiosul- phate, 28 grammes to the litre, and then titrating it with ^ iodine and starch mucilage and diluting the hypo until it is exactly equivalent to the iodine solution, the ^ iodine solution is made by dissolving 12*59 grammes of pure iodine and 18 grammes of potassium iodide in 200 cc of distilled water, the solution being effected by constant agitation, when this is complete, distilled water is added to bring the whole up to i litre, i cc = 0-01259 gramme iodine (the T % iodine solution is only required for titrating the " hypo," if the 7 N iodine has been accurately prepared, and the strength of the "hypo" solution determined by it, it is not necessary for the " hypo" solution to be of exactly ^ strength, since if we know its value in terms of iodine we can make the necessary calculations). 3. A i : 10 solution of potassium iodide. 4. Some pure chloroform. 5. Starch water ; made by carefully mixing one part of of starch with 500 parts of cold water and boiling briskly for five minutes, and if necessary filtering. Apparatus 1. Burette graduated to ^ cc. 2. Two stoppered flasks of 50 cc capacity. 3. Two stoppered bottles of 12 oz. capacity. Detail. Carefully weigh into the stoppered flask, 0*8 gramme of butter, then add 10 cc of chloroform, and 25 cc " Hubl's reagent," if clear the bottle may be closed and set aside, but if turbid a little more chloroform must be added until it is clear, the flask is then closed and placed in a moderately warm place (about 70 to 75 F) for eight hours. A control test labelled control is done at the same time, in precisely the same way, with chloroform and " Hiibl's reagent" but no butter. After the eight hours have elapsed, add to each flask 20 cc of the i : 10 potassium iodide, and 50 cc of distilled water, transfer the contents to labelled 12 oz. stoppered bottles and rinse out with distilled water, and then add more water, so that with the rinsings the whole measures 150 cc, then each botlte is titrated with the' 1 hypo," as in the Forchammer process using the starch water as an indicator. An example will explain the calculation The sample required 11 cc ^ Na. S a O 8 to just discharge the colour. The control took 30 cc ^ Na a S 2 O, to just discharge the colour. The difference = 19 cc ,* Na 4 S 4 O 3 . Now each i cc T Na a S a O 3 == 0^01259 gramme iodine, .'. 19 cc T * Na 2 S 4 O 8 = 19 X '01259 grammes iodine, this = 0*24 (nearly) and since we took o'8 gramme butter 0-24 x ioo then = 30*0 per cent, iodine absorbed. 0-8 The iodine absorption of butter ranges from 23 to 38 per cent. Margarine ... ... from 40 to 55 per cent. *Beef fat ... ... 34 ,, 45 Lard ... ... ... 52 62-5 Linseed Oil ... ..'. ,, 173 ,,187 ,, Cod liver oil ... ... I587,,i66'6 ,, There are other modes for determining the purity of butter, such as the Valenta acetic acid test, Koetstorfer's process, etc., and the reader is referred, for the details of these * A short Manual of Analytical Chemistry by Muter, eighth edition, 1898, Bailliere, Tindall & Cox. 162 processes, to other works on Food Analysis, such as Muter's* or Pearmain and Moor's.* Preservatives in butter : Boric acid is the commonest, and [is detected in the ash as shown in the chapter on milk. Salicylic acid may be detected, if present, by adding a strong aqueous solution of sodium bicarbonate, and adding to the extract thus obtained, which contains sodium salicylate, some dilute sulphuric acid, then extracting with ether, evaporating to dryness and adding a drop of ferric chloride, a purple violet colour is seen if salicylic acid be present. * Bailliere, Tindall & Cox, King William Street, Strand. 1 63 CHAPTER IX. WHEAT, FLOUR, AND STARCHES. Flour should be prepared from wheat by the process of milling and sifting, which removestheoutercoatsandleavesonly the central portion of the grain which consists principally of starch, but also contains between 10 and 12 per cent, of nitro- genous substances, a small percentage of fatty matter, and some sugar. There are numerous kinds of wheat grown for the production of flour in England, most of the wheats are known as red and white wheats, which are varieties of Triti- cum hibernum or winter wheat, and there is also another variety known as the awned or bearded wheat, which is less common. Before entering into a full description of wheaten flour it is well to know the characters of good wheat, the colour of which should not be too dark nor the furrow too deep, it should have no unpleasant smell, show no signs of disease, or the ravages of insects, and should be of good weight; a bushel of good wheat should weigh about 63 Ibs. or 64 Ibs., the drier the wheat the heavier it is, because wheat being very hygroscopic, swells if exposed to moisture, and therefore a smaller number of grains go to the bushel. If a grain of wheat be soaked in water and then dissected with needle and forceps, it can be shown to possess four distinct coats surrounding a central network of cellulose containing starch grains. The diseases likely to be met with in wheat are those due to vegetable parasites, chiefly belonging to the family of Ustilaginea- (the bunts or smuts), and also rust or mildew (Pucctnia graminis}*v;\\\c\\ belongs to the order of ALcidiomy- cetes; this rust attacks during the summer the stems, leaves, and glumes of wheat, its appearance is well shown in the accompanying figure {Fig. 41 B} which shows numerous two- celled teleutospores borne by hyphae threads growing out from the epidermis and sub-epidermal cells. The rust parasite is one possessing considerable interest to botanists, as it forms spores *A theory was broached in 1891 by Mr. N. A. Cobb and the late Mr. Sidney Olliff, which was published in Vol. II., Part II., Agricultural Gazette, N.S.W. That the singular immunity from rust of American wheat is due to the larva of the Hessian fly (Cecidomyia destructor) feeding on rust when obtainable in preference to the juices of plants. 164 of two distinct types at different seasons, in the summer, one- celled rounded reddish-brown groups of spores are formed in the situations already mentioned, and these cells are called uredo-spores, whereas the teleuto-spores here depicted grow in spring on the leaves of the barbery, this change of hosts with the season of the year, and at the same time alterations of habit, are the chief points of interest to naturalists. Fig. 41. DISEASES OF WHEAT. Tilletia caries known also as Uredo foetida or 'bunt,' (Fig. 41, A) attacks the interior of wheat grains and is seen as round light brown spores reticulated on the surface. " Smut " (Fig. 41, E} is caused by the Uredo segetum or Ustilago carbo, ears of corn attacked by it are quite black, and the interior of the grain is replaced by brown circular spores, the surface or episporium is smooth, and this under the microscope readily 65 distinguishes it from "bunt." A sample of wheat which has been adulterated with rye, or flour prepared from grain which has been mixed with rye, may show the mycelial fungus Claviceps purpurea, (Fig- 41 < D} which in a microscopic section is not unlike a composite flower, the circumference is seen to be packed with small flask-like bodies (perithecia] \vhich are faintly purple in colour ; from these flask-shaped bodies the spores are formed. Animal parasites which attack grain are the common weevil (Calandra granaria), a small coleopterous insect which can be seen with the naked eye. The female insect makes a little round hole in the grain and deposits an egg in it, from which a larva is hatched in due course, which feeds on the contents of the grain. Occasionally the disease known as "ear cockle " is met with in dark discoloured small-sized grains which have been kept in a damp place ; under a low power objective these are seen to consist of small worms (Anguillulx or vibriones tritici) about a A to a 1 * inch long. (Fig. 41, C}. Flour of different qualities, having distinct trade names, is met with in commerce. Thus the best flour is known as best or superfine, then come seconds or middlings, a still coarser kind is known as thirds, and lastly, we have pollards or bran flour. The composition of flour and whole wheat is shown to be : 5 JS o -J3 ^i fi || h. 1 5 -S s 2 .5 & " Fine White 1337 10 21 0-94 2-35 3-06 69-30 0'29 0-48 Flour Coarse Flour I2'8l I2'O6 1-36 r86 4-09 65-88 0-98 0-96 Whole Wheat * i3'37 12-04 1-91 69-07 ~ I 90 ,- 7 i The nitrogenous substances consist of a globulin and an albumose, which when acted upon by water form gluten. A good flour should yield between eight and twelve per cent, of gluten, if there is a deficiency in the amount of gluten, or if the flour has undergone deterioration by being kept in a damp place or by being kept too long, it is impossible to use it for bread-making ; much of the flour which has undergone this *K6nig, i., 619, and ii., 519, quoted on p. 397 Law and Chemistry of Food and Drugs, by Robinson & Cribb. i66 deterioration to a limited extent can however be rendered usable by the addition of alum ; alum then, if there were no other things against it, would be objectionable because of its rendering an inferior flour capable of being used, but, as we shall see later, there are other even graver objections to its use. Good flour ought to be of a white or faint cream colour, should not taste acid and have no smell of hiustiness; when rubbed between the hands it should feel soft and velvety, and cohere slightly when pressed together; if mineral matter has been added, or if it has been allowed to get damp it will feel gritty ; it should smell sweet, and there should be no excess of bran, which would give it a brown colour. Damp or inferior flour may contain any of the di- seases previously mentioned such as vibriones tritici, and weevils ; damp flour is also liable to contain meal mites (Acarus farina?) which are very similar in appearance to the Acarus scabei; the diseases such as rust, bunt, smut and ergot should be sought for with a microscope. If mineral matter has been added it is shown by excess of ash, (i.e. over two per cent.) ; 0^48 per cent, is given as a normal amount of ash obtainable from fine wheat flour, but some authorities give it as ry per cent, on an average and 0'8 as a minimum. If the amount of ash is excessive it should be tested for carbonates, sulphates, alum, alumina or silica. Carbonates are shown by effervescence with dilute hydro- chloric acid.andexcess of sulphates by a heavyprecipitate when barium chloride solution is added to a solution of the ash acidified with dilute hydrochloric acid. The detection of alum (i.e. potassium or ammonium aluminium sulphate) will be detailed later. Silica and silicates are shown by their being only slightly soluble in water after the addition of dilute hydrochloric acid and on evaporating to dryness and heating to 140 or 150 C a residue is left, which, after adding a little dilute hydrochloric acid, consists of a white gritty powder, alumina is to a slight extent naturally present combined with silica as clay, and for every part of silica present, one part of alum is deducted from the total alum found, and it is the excess of alum so found which constitutes the adulteration. Lead should also be sought for in the ash, since a case is recorded by Alfprd of some millstones in which holes had appeared and which were repaired by filling them up with lead. Mineral matter in flour may also be detected by taking about 5 grammes of the flour, s'haking it up with 30 or 40 cc of chloroform in a separator or long narrow cylinder; if mineral matter be present it will sink, whereas the starches and proteids i6 7 rise to the surface. The amount of moisture in good flour should not exceed 16 or, at the most, 18 per cent. ; the usual amount in the best samples being between 10 and 14 per cent, of moisture. Moisture is determined by weighing a certain amount of flour, drying it at a temperature not exceeding 100 C until it attains a constant weight, the loss in weight gives the amount of moisture in the sample taken, this is then calcu- lated to percentage. The flour, after drying, is incinerated to a white ash and the ash calculated to percentage. Gluten is estimated by taking a certain quantity of flour r making it into a stiff dough, and then gently washing it until the water in which it is washed ceases to become turbid and shows no starch with iodine, and there remains an elastic mass (gluten) which, after being dried over a water bath or in a water oven should, on calculating to percentage amount to- some 10 or 12 per cent. Ergot in flour may be detected (2'.) by the smell of trimethylamine which arises when a solution of caustic potash is mixen with ergotised flour. (zV.) By adding to the above test dilute nitric acid until it is slightly acid, and then once more adding dilute caustic potash solution until it is neutral, when a violet colour appears. (iii.) Another test is to- take 2 grammes of flour, add 10 cc of 70 per cent, alcohol, and then some 5 per cent, hydrochloric acid, an orange- yellow colour will now be seen if ergot be present. Hut there are other things such as the weed corn-cockle (Agrostemma githagct), Loliurn ; or beans, all of which also show this reaction. A saponin derived from corn cockle (Agrostemma githago} known as agrostemma-sapotoxin has been described by R. Kobert (Chem. Centr. 1893 i. 32) the formula for which is C 17 H 28 O 10 (Alfred H. Allen, Commercial Organic Analysis, Vol. iii, Part iii, p. 123). This substance is absorbed by the subcutaneous tissue, and the large intestines, the symptoms of poisoning by it are, intense muscular weakness, increase in the rate of respiration, and finally death from asphyxia; after death, fulness on the right side of the heartland intense congestion of the intestines are seen. Lolium temulentum or Darnel is a grass belonging to the tribe Hordes?, it sometimes grows to a dangerous extent amongst wheat, and so may be gathered with the wheat and ground up with it; it has a poisonous action if present to any appreciable extent, and gives rise to a burning pain in the throat, nausea and vomiting, drowsiness, vertigo, and occasion- ally staggering gait, convulsions, and hallucinations, have been observed ; it is detected by making an alcoholic extra6\ of the suspected flour, which, if lolium be present will be coloured 1 68 greenish, and have a disagreeable taste not found in an alcoholic extract of good wheat flour free from lolium. Other vegetable adulterants consist of barley, rye, bean, pea, potato, maize, oats and rice, these would not probably be added in times of plenty, they are not actually harmful, but for the most part less nutritious than wheat, the leguminosae excepted, and these adulterations would tend to spoil the appearance of the bread. Maize under certain circumstances, may be actually harmful, for example, the em- ployment of maize that has undergone partial decomposition is very objectionable, for during decomposition two distinct poisons are developed, one being a narcotic and the other a mus- cular excitant producing spasmodic contractions, and again, maize that has become diseased (verdet) produces a disease re- semblingergotism in many ways, which has been known for num- bers of years in Italy as pellagra (pellis, a skin or hide, and Gr : agra seizure). The skin affection was formerly the symptom chiefly considered, but it is now known that grave nervous disorders are connected with the disease such as melancholia w r ith suicidal tendencies, and there are also spasmodic con- tractions of various muscles, and gastro-intestinal disturbance. The various foreign meals are recognised by the starches they contain. Starch granules are composed of two substances, granulose and erythro-granulose enclosed in an envelope of starch-cellulose, the granulose is soluble in dilute mineral acids and saliva, and coloured blue with iodine, the cellulose is not dissolved by the acid, and is coloured brown with iodine ; by boiling, the contents of the cells swell, burst the enclosing walls and are set free as " soluble" starch; starch grains are .as a rule more or less laminated, the markings which appear as a result range more or less around a certain point variously shaped in the different grains, this point being known as the hilum. The shape of the starch grains, the markings, position .and appearance of the hilum, are the points upon which we depend for the identification of the species. Starch grains in general, as well as those of the particular f rains liable to be be met with in adulterated flour will now e described. They may be divided into two principal classes 1. Those with an even contour. 2. Those with an irregular or facetted outline. Group i. may be sub-divided into (a) Round or oval granules without any markings or :6 9 hilum (barley and wheat), Figs. 42, 43, or with a starred hilum (rye). Fig. 44. (3) Irregularly oval or oyster-shell shaped with distinct concentric markings and a well-defined hilum at one or other end (Potato, Arrowroots) Fig. 4$. (c) Oval kidney shaped granules, with faint concentric markings and a linear hilum starches of leguminous plants such as peas and beans. Figs, 46, 47. Group 2. is sub-divided into {a) Facetted grains (maize, oatmeal and rice). Figs. 48, 49, 50. (b) Irregularly facetted or truncated, i.e., like irregular logs with the branches lopped off (sago and tapioca). Figs. S f > 5 2 - The various starches may be arranged according to size and their distinguishing marks Potato grains are as a rule large, they vary from *a to 5 of an inch in their longest diameter, the large cells predominat- ing, and the hilum is as a rule at the smaller end. In arrowroot the grains are for the most part smaller than those of potato, except in the case qf tous-les-mois arrowroot, which are larger, and have the hilum at the large end. Sago grains, irregularly truncated and many flask shaped cells. Bean and pea. Bean starch is usually somewhat larger than that of pea, and the hilum is more irregular. Rye consists of large and small circular cells, (Fig. 44) some of the larger ones having a star shaped hilum, wheat and barley (Figs. 42, 43) circular and without hilum, the former consisting chiefly of very large and very small size granules, whereas the latter shows many of medium size. Tapioca grains (Fig. 52) are small, they are irregular in shape, show many goblet shaped cells somewhat smaller than those of sago, (Fig. 57) and also have a more or less circular hilum. Maize are very characteristic polygonal cells, with well- marked star shaped hilum. Fig. 48. Oats are angular cells tending to adhere together in rounded masses. Fig. 49. Rice are small angular cells often seen to be grouped in twos and threes. Fig. 50. 1 7 o Fig. 42. WHEAT STARCH, x 400. Fig. 43. BARLEY STARCH, x 400. 171 o /^. 44. RYE STARCH, x 400. Fig. 43. POTATO STARCH, x 300. 172 Fig. 46 PEA STARCH, x 300. Fig. 47. BEAN STARCH, x 300. '73 /g' 48. MAIZE STARCH, x 400. F/^ 49. OATMEAL STARCH * 400 UNIVERSITY '74 * & ^ u * oH Q c? ^ tD o /'g- 50. RICE STARCH, x 400. tg'* 57. SAGO STARCH, x 400. '75 Fig. 52. TAPIOCA STARCH, x 400. i 7 6 CHAPTER X. BREAD AND BISCUIT. Bread should be made from the finest wheaten flour. Long experience has shown that the advantages which were at one time supposed to accrue from the use of whole-meal are more than counterbalanced by the irritating effects on the bowels, caused by the bran particles it contains. Bread should be well-baked, show between 20 and 30 per cent, of crust, which should be firm but not burnt, the crumb should be aerated, not unduly moist, show no evidence of moulds, (Figs. 53 and 54) and not taste sour when eaten. The crust should always be estimated when reporting on a sample of bread. To do this, the loaf is first weighed, then care- fullypared with a sharp knife, taking care to remove all the crust but none of the crumb, it is again w r eighed and the loss in weight gives the amount of crust, the crust and crumb are then calculated to percentage and in all subsequent tests a proportionate amount of each is taken. Moisture is estimated by taking 10 grammes of bread (with a due proportion of crust as noted) and drying in a water-oven or air-bath at a temperature of 90 C. for at least three or four hours. The loss of weight gives the amount of moisture, which is calculated to percentage. Bread contracts are always made in such a way that the loaves, after being well and properly baked, shall, as required, weigh 4 Ibs., 3 Ibs., 2 Ibs., or i Ib. each respectively at the time of delivery, such time to be within 24 hours, but not sooner than 12 hours after being baked. The loss from evaporation in bread amounts to 8 per cent, in one day and about 14 per cent, in seven days. Bread which has been baked over 48 hours commences to taste stale, this is in a great measure, but not entirely, attributable to loss of moisture, since by moistening it and re-baking, the bread is restored to its former freshness for a little while, but then quickly becomes stale, staleness is in part due to changes in the bread brought about by micro-organisms and moulds. Fig. 53. ASPERGILLUS GLAUCUS. x 240. Fig. 54. MUCOR MUCEDO. x 240. T 7 8 Having calculated the moisture, the dried bread is burned at a low red heat until it consists of a charred mass, this is then pounded in a mortar, taking care to avoid any loss, and returned to the platinum dish and burned to a white ash, the ash should be slightly over i per cent, and under 3 per cent., but I have examined many good samples of bread showing amounts of ash varying between 0*75 and 1-5 per cent.; if the ash be strongly alkaline in reaction it shows that excess of potato has been used in the process of " feeding the ferment," or in some other stage of bread making, except in the case yvhere the bread itself is alkaline, in which case the alkalinity is due to sodium carbonate added in the process of bread making. Acidity is estimated by taking 10 grammes of bread (including a due proportion of crust), macerating it for one hour with distilled water, straining or pouring off the clear fluid, and titrating with deci-normal soda, not more than i cc of this should be necessary, and the best indicator is delicate litmus paper, phenolphthalein or methyl orange are not suffi- ciently sensitive. i cc of y NaHO = O'oo6 gramme of glacial acetic acid (HC 2 H 3 OJ, this is calculated to percentage and to grains per ID. A good bread will, as a rule, show on an average about 3*5 to 5-0 grains per Ib. of HC 3 H 3 O a , but a bread need not be condemned as sour unless it exceeds 12 grains per Ib., which should be the extreme limit. Example : 10 grammes of bread treated as directed con- tained acid equivalent to o'g cc of . NaHO, i.e., = o'g x O'oo6 gramme HC 2 H 3 O 2 = 0*0054 HC 2 H 3 O % for 10 grammes, which is the same as 0^054 per cent, acetic acid. Since there are 7000 grains in i Ib. if we multiply the percentage amount by 70, it gives the answer in grains per Ib. in this case equal to 378 grains per Ib. of glacial acetic acid. Where greater accuracy is required 20 grammes of bread are taken and placed in a wide-mouthed stoppered bottle con- taining 200 cc of rectified spirit, the bottle is then closed and left for some hours, when 100 cc of the clear spirit are de- canted and titrated as before mentioned. Alum. The advantages of alum from a baker's aspect are that by its use an inferior and otherwise useless flour can be employed, since alum prevents fermentative change, result- ing in the production of diastase, which is an albuminous sub- stance of an unknown composition produced in the process of germination, this diastase is an enzyme and is capable of transforming starch into maltose and dextrine, the diastase is produced at the expense of the nitrogenous substances in flour and gives the bread a sweetish, dark, and unpleasant appear- ance. Alum also helps to make the bread light and of a good colour; it is used in inferior baking powders chiefly on account of cheapness. From a health point of view alum cannot be too strongly deprecated, as -it renders the nitro- genous substances in flour indigestible, interferes with all the digestive processes, forms insoluble salts with phosphates, and may, if used in baking powders with water and soda, act as a purgative through the formation of sulphates of soda, and if potash alum A1 2 (SO 4 ) 3 K a SO 4 24!-!., 6 be the one em- ployed, then K 2 SO 4 may be set free, which acts as mild purgative, the dose of which is from 10 to 40 grains. Alum is detected in bread by making a fresh tinclure of logwood chips (5 grammes) with 70 per cent, alcohol (100 cc) also a 15 per cent, solution ammonium carbonate. A drachm of each of these added to a wineglassful of water and poured over a slice of the suspected bread, turns it a rose-pink colour which soon turns to a lavender-purple colour if alum be present, and persists for at least 24 hours, whereas if no alum be present the bread soon turns brown ; in this colour test alum plays the part of a mordant. If the logwood test shows a persistent mauve colour on drying for say 12 or more hours then it is advisable to make a quantitative estimation, this is best done by the method detailed in Muter 's Manual of Analytical Chemistry, 8th edition, p. 180., in which it is advised to take 100 grammes of bread, reduce to a white ash, then add 5 cc of fuming HC1, cover with a glass plate and leave it for 15 minutes, then add 25 cc of distilled water, and boil gently for five minutes, after which filter. The insoluble matter (clay and silicious matter) is washed, the washings added to the filtrate, and the latter mixed with y.c of strong liquor ammonia and 40 cc of acetic acid. Since the ash of bread contains much phosphoric acid, the precipitate will consist of aluminium phosphate with some ferric phosphate, the precipitate is filtered off, washed, dried and ignited. If the amount obtained now, does not exceed 5 milligrammes, there is no need to proceed further, as the, alum could only be present in small quantity, but if it does exceed 5 milligrammes, the amount of iron present must be determined, and subtracted from the total amount of precipitate, each milligramme remaining after this, being considered as i grain of alum per lib. loaf. It is generally allowed that ordinary flour contains, normally, about 0*042 per cent, of phosphate of alumina, so that this amount reckoned as alumina must be deducted from the total amount of alumina found. When i8o alum. Al, (SO 4 ) 3 (NH 4 ) 2 SO 4 , 24H 2 O is added to bread, i.e. when bread is adulterated with alum it is usually to the extent of 5 to 10 grains per Ib. Sulphate of copper is not known to be used as an adul- terant in England, though it is generally believed to be used in small amounts on the Continent, a few drops of Potassium Ferrocyanide placed upon a slice of bread containing copper gives a reddish brown colour. Biscuit has, from time immemorial, been the substitute for bread at sea, for the reason that bread will not keep long, as apart from loss of moisture, it develops a disagreeable taste characteristic of staleness. Biscuit contains very much less moisture than bread, and not being prepared by any fermentative process does not become stale; if kept from the effects of damp and insects, it will keep good for 6 or 7 years or possibly longer, and only requires to be re-baked to make it crisp and fit for use. At one time biscuit was kept in sacks, which afforded no protection against rats, insects and damp, later it was packed in casks, and at the present time it is sent out in hermetically sealed tins, protected from injury and variations in temperature by an outer casing of wood. The weight of biscuits supplied to the Royal Navy m ustbe such that not less than five go to a pound, they are hexagonal in shape ; when biscuits are cut square or hexagonal, the waste, which is unavoidable with circular biscuits, is avoided. Biscuit is made by mixing flour and water into a firm paste, which is rolled by steam rollers, cut by a stamping machine, baked in a quick oven and finally dried in a hot drying loft, and when quite dry, packed in tin-lined cases, which when filled, are hermetically sealed. Biscuit should be of a light brown colour, not burnt, the outer surface should be firmly adherent to the part beneath, it should be dry, give a ringing sound when struck, be readily broken in the hand, not fall to dust, the broken portions should be somewhat flaky, free from discoloration, have no un- pleasant odour or mouldy taste, should be readily dissolved by the saliva, and pieces of it should float in water, and show no evidence of insects. When baked in an oven for a few minutes at a temperature of about 2i2F, biscuit should become crisp and palatable. Although bulk for bulk biscuit contains more nitrogenous matter and more carbohydrates than bread, it is les* nutritious, the great variety in taste, of different breads is lacking in biscuit, so that one is apt to tire of biscuit. Navy biscuit analysed by me at Haslar, showed the following per- centage composition Moisture Proteids Carbohydrates cellulose & fat (by difference) Salts 9-69 io'gi 78-4 x*o The percentage composition of Navy biscuit according to Dr. Church is Moisture Proteids Fat Starch and Dextrine Cellulose Salts IO'2O 10-90 1-60 75-00 I'2O no 182 CHAPTER XI. LIME JUICE. Lime juice was, on the recommendation of Sir Gilbert Blane, introduced experimentally into the Royal Navy as a remedy against the ravages of scurvy* in 1795. although Woodall had advised its use as a remedy against scurvy as early as 1617. In 1796 it was issued to all ships, and we are told that within one year after its introduction scurvy had become an extinct disease. Lime and lemon juice supply potash to the blood in a form which can be assimilated ; potash salts in which the acid radicle is a mineral one, or citric acid alone, have little or no anti-scorbutic action, but when citric acid or citrates of potash are employed in the form in which they are met with in such juices as those of the lemon or lime, then the action is seen at its best, the citric and other vegetable acids become changed in the blood into carbonates ; the ash of plants, or ash resulting from the incineration of vegetable juices like those of the lemon or lime, are likewise alkaline from a similar cause. Scurvy appears when there is a deficiency of potash salts in the blood which gives rise to haemolysis since theprincipal salts of the red blood corpuscles are those of potash ; this deficiency is generally caused by a want of a proper pro- portion or an absence of fresh vegetables or fresh meat. When salt meats and preserved foods form the sole dietary there is a deficiency in potash and an increase in the amount of potash excreted, in other words there is a reduced income and an increased expenditure, the latter being due to the ingestion of sodium chloride which tends to cause a greater loss of potash than occurs at such times when salted provisions are not the principal foods. Whether or not scurvy is a disease of microbic origin as has been stated, there is no doubt but that the disease only exists amongst those who have been deprived of their daily quota of potassium in such form that it may be assimilated, and the blood in these cases has in consequence become profoundly altered ; if the disease be due to a microbe, the altered condition would explain how the blood has been rendered incapable of resisting the specific organism credited with the causation of scurvy by certain pathologists. * The mortality from scurvy in 1780, according to Sir Gilbert Blane, amounted to one in seven of a force of 7000 to 8000 men employed in the West Indies. Lime juice is the expressed juice of the Citrus limetta, fortified by the addition of about i ounce of brandy to each 10 ounces of juice. Samples which I have examined at various times show as a rule the following : . Grains per Sp Gr Per cent. ounce citric acid H S C, H.O, at 60 F. as issued. Alcohol, vols. Total solids. Ash. 23 or 24 up to 27 T022 4 r 5 8 to 8-5 0-28 to o'45 The examination is conducted as follows: Into a tall glass cylinder pour out some of the lime juice, note the smell, taste, colour, and appearance ; the odour should be agreeable, the taste palatable and sharp, but not bitter, the colour that of amber, and the fluid should be clear and free from stringiness or deposit. Specific gravity is taken at 60* F.. preferably with a Westphal's balance, but a urinometer will answer sufficiently well for rough purposes, the specific gravity should be about ro22 or 1-023. To determine the amount of alcohol present the lime juice is now evaporated to half, and then made up to the original volume with distilled water, and the specific gravity again taken at 60 F. ; if now we subtract the first specific gravity from the second specific gravity and subtract this number from 1000, we can on reference to the alcohol table on p. 202, read off the amount of alcohol present. Free acidity is determined by taking i cc of the lime juice, adding about 20 cc of water, and titrating with JJ. NaHO, using phenolphthalein as an indicator ; each i cc of the ^ NaHO used equals 0-007 gramme of citric acid H 3 C a H 4 O T H 4 O 1 or C 8 H 4 (OH) (COOH) 8 H 4 O, the amount thus found multiplied by 100 gives the percentage amount, and this per- centage amount multiplied by 4/375 gives grains per ounce. If it is required to determine the citric and other combined acids, the reader is referred to Pearmain & Moor's Analysis of Food and Drugs (Bailliere & Co.). The ash should be alkaline, it is therefore dissolved in 1 84 water and the reaction taken. In some lime juice tested by me the alkalinity of the ash was equal to 0*145 P er cent. KHO. Adulterants : The lime juice may be purely factitious and made up of citric acid (generally about 7 or 8 grains per ounce) and flavouring agents, in which case on evaporating there will not be any characteristic aroma. Sulphuric acid is detected by the barium chloride test as described under water tests, and can be estimated by Hehner's method, which consists in evaporating to dryness 50 cc of the lime juice together with 25 cc ./I NaHO in a platinum dish, igniting to a white ash, then adding 25 cc T * HC1 to neutralise the T N NaHO previously added ; if now we heat to expel CO.,, filter and wash the filter with warm water and the wasti- ings mixed with the filtrate, on titrating with .^ NaHO and phenolphthalein, the amount required to neutralise the solu- tion is proportional to the amount of sulphuric acid present, the number of cc ^ NaHO multiplied by 0^0049 gives the amount of free sulphuric acid in 50 cc of the sample, and this multiplied by 2 gives percentage. Hydrochloric and nitric acid can be detected as in the qualitative water tests. Tartaric acid C 4 H ft (OH).(COOH), (H, C 4 H 4 O 6 ) is detected by adding to some of the lime juice diluted to half, some acetate of potash solution, this is mixed well and set aside to stand for 24 hours, after which, if tartaric acid was present, the crystals of acid tartrate of potash K HC 4 H 4 O 6 will have fallen, these are small rhombic crystals only sparingly soluble in water. Lime juice is issued on board ship after the ship's company has been 10 days on salt provisions, half-ounce of lime juice and half-ounce of sugar to everyone. In the tropics the engine- room department receive double the quantity of sugar and lime juice. CHAPTER XII. COCOA, TEA, AND COFFEE. Cocoa is prepared from the seeds of the cocoa-palm (Cacao theobroma), and several plants of the natural order Byitnertacece. It is obtained chiefly from the West Indies, Venezuela, and Ecuador. That from Venezuela being the most esteemed, after which comes that from the West Indies It is issued to the Navy in the form of chocolate, ana forms a most valuable article of diet. The Naval chocolate is divided into two kinds, ordinary and soluble, both are made from the same description of seeds, which when prepared as described below, are mixed in the following proportions : One-sixth to one-fifth of Grenada cocoa beans. One-fifth to one-third of Guayaquil cocoa beans. One-half to three-fifths of Trinidad cocoa beans. The cocoa in the above proportions is finely ground and mixed with one-fourth or one-fifth of its weight of raw sugar, forming ordinary chocolate, and when mixed with a slightly larger proportion of granulated refined sugar and one-fourth of its weight of arrowroot or sago-flour, forms the soluble variety. Ordinary chocolate is packed for the Navy in cases of 50 Ibs. or 100 Ibs. capacity. Soluble chocolate is packed in cases holding 25 Ibs. In the natural state cocoa seeds are contained in pods, having an elliptical-ovoid shape, from 7 to 10 inches in length and 3 to 4^ inches in diameter, each fruit contains from 20 to 40 or more seeds. The pods when ripe are either buried in the earth until the pulp becomes rotten, or else allowed to undergo a process of fermentation for five days in earthen jars, in order to separ- ate the seeds from the pulp. Those which have been buried are said to yield the best cocoa. The seeds are about the size of an almond, and according to Payen have the following percentage composition : 1 86 Fat (cocoa butter) ... ... 52*0 Nitrogenous compounds ... ... 2O'o Starch ... ... ... io'o Cellulose ... .. ... 2*0 Theobromine ... ... ... 2'o Salts (consisting largely of phosphates) 4 - o Moisture ... ... ... io'o Cocoa-red, and essential oil ... Traces lOO'O The seeds, after they have separated from the pulp, are picked out and dried in the sun or in ovens, after which they are roasted in iron cylinders at a temperature of from 500 to 600 degrees Fahrenheit, the temperature being regulated according to the variety and quality of the cocoa beans ; roasting develops the aroma and flavour, and when complete the cocoa is allowed to cool on the floors for about 12 hours, after which it is slightly crushed and shelled, then winnowed and sifted in order to prevent loss from portions of the nibs adhering to the husk. A substance possessing a composition such as that shown above should be both nourishing and stimulating, and such it undoubtedly is. In the chocolate supplied to the Navy none of the fat is removed, this accounts for the oil which is seen on the surface of the boiled chocolate issued from the galley on board ship, the excess of fat in most of the cocoas and choco- lates met with in commerce is removed, and in some cases saponified by alkalies. The use of alkalies is a practice to be deprecated, and has arisen from the dislike which many con- sumers have to greasy cocoas. Theobromine which is contained in cocoa is a powerful alkaloid, having the chemical formula C H a (CH J 2 N 2 O 4 or C 7 H 8 N 4 O,, a homologue of caffeine. C 8 H 10 N 4 O t . Prepared cocoa contains from 1*3 to i"j per cent, theo- bromine. Coffee from O'8 to ro per cent, caffeine. In the examination of chocolate an important point to observe is whether or not it has been attacked by the larvae of the chocolate moth Ephestia elutella ; these honeycomb the chocolate and spin webs over it, and in consequence careful precautions to prevent the ravages of the chocolate moth are taken by Admiralty authority, no chocolate being allowed to be stored in the same building as that in which the process of manufacture is going on, as soon as the chocolate is packed in the cases lined with tin-foil, these are thoroughly lime-washed externally and removed into store. 1*7 The analysis of cocoa or necessary. The following is composition : Navy ordinary Chocolate chocolate would not often be the approximate percentage Water 2-25 to 3*0 Water Fat 45-50 to 46-0 Fat Ash 3-0 Ash Cellulose ... 3-0 Cellulose Nitrogenous j Nitrogenous matter matter including 17 to io - 25 including Theobromine J Theobromine Starch 8-00 Starch Sugar 20'00 Sugar Navy soluble Chocolate. lOO'OO 45 33*4 2'0 2'0 28-0 25-0 lOO'O Theobromine which contains 31- 1 per cent, nitrogen (Pearmain & Moor) is estimated by drying a given quantity of chocolate and extracting it with petroleum ether which dis- solves the fat, sugar, theobromine, etc. ; this extract is dried at 1 00 C. over a water bath to remove the petroleum ether, and the residue extracted with alcohol of 78 per cent, strength, this dissolves amongst other things the theobromine, the alcohol is then driven off by drying the alcoholic extract over a water bath, and the residue dissolved in water and clarified with lead acetate solution, the lead being subsequently re- moved by passing a stream of sulphuretted hydrogen through the solution ; the theobromine is then obtained from the liquid by adding chloroform and shaking the whole repeatedly in a separator, the layer containing the chloroform is drawn off, the chloroform evaporated, and the residue consisting of theo- bromine weighed and calculated to percentage. The fat is estimated by extracting a given quantity of chocolate with petroleum ether, filtering and weighing the residue from the dried filtrate, and calculating to percentage. Ash. The residue left after extracting the fat is burnt and the ash weighed ; this should amount to 3 or 2 per cent., according to whether the sample be one of ordinary Navy or soluble Navy chocolate; pure cocoa should yield about 5 per cent. ash. Soluble Extract. 5 grammes of chocolate are rubbed up in a mortar with 250 cc of water until a perfect emulsion results, this is well shaken in a separator and allowed to stand for 10 or 12 hours, after which the thick undissolved portion is removed and the clear supernatant fluid obtained and filtered, a portion of this forming an aliquot part of the whole, i88 (say 50 cc) is evaporated to dryness in a tared platinum dish and the dried extract weighed and calculated to percentage, the cold water extract in the case of cocoa (not chocolate) samples should not, according to Pearmain & Moor, exceed 18 per cent., who say that "any material excess beyond this will probably be due to added sugar."* The residue left after performing the above determination is burnt, and the ash calculated to percentage shows the amount of soluble ash, which in ordinary cocoas should not fall below 2'o per cent.t TEA. Tea consists of the dried leaves of Camellia theifera or sinensis (Thea sinensis} ; natural order, Ternstromiaceae. On the market there are two principal kinds of tea, viz., green and black, the difference in colour being due to the mode of preparation, the green tea being dried rapidly and the black tea slowly, so that a form of fermentation occurs and the leaves turn black. Various leaves have been employed from time to time for the purpose of falsification, the leaves of haw- thorn, elm, oak, poplar, sloe, elder, and beech have all been met with in samples, these are readily detected by spreading out the leaves on microscopic slides after an infusion of the so-called tea has been made ; the leaves of the tea plant are lanceolate in shape and from i^ to 2 inches in length, and about \ inch to f inch wide at the broadest part ; on holding up the leaf to the light the venation is seen which is quite characteristic ; the veins run out from the midrib nearly to the border and then curve slightly forwards and inwards, the veins of leaves other than tea being continued to the edge. The leaves which bear most resemblance to tea leaves are those of the willow and sloe. Willow leaves are longer and narrower, and the serrations are coarser and shallower ; the sloe leaves are more deeply serrated, and the leaf is broader and more ovate. Tea leaves which had been previously in- fused were at one time faced with a mixture of Prussian blue, turmeric, and calcium sulphate, and when dried and rolled, sold as green tea ; others faced with black lead, dried and rolled, being passed off as black tea. The detection of exhausted leaves is most easily accomplished in the ash as detailed below, exhausted leaves yielding much less soluble ash than those which haVe not been used. *Aids to the Analvsis of Foods and Drugs, by T. H. Pearmain & C. G. Moor London Bailliere, Tindall, & Cox. t Ibid., p. 87, 2nd edition. i8g The following table shows the percentage of the chief constituents of dry tea : Caffeine . Tannin. Cellulose. Total Ash. Soluble Ash. Water. 1-8 to 3-5 12 to 15 20 to 22 5'4 to 7 2-8 to 4 4 to ii As far as we are concerned it will suffice to estimate the moisture, total ash, and the soluble ash. Moisture is determined by drying 5 grammes to a con- stant weight and calculating to percentage. The total ash is found by incinerating the dried tea at as low a temperature as possible, if this amounts to more than 8 per cent, it shows mineral adulteration. The soluble ash is found by pouring boiling water on the total ash and filtering, the ash is washed repeatedly and the washings filtered, then the filtrate is evaporated to dryness, weighed and calculated to percentage ; this should not fall below 3 per cent. In exhausted leaves the soluble ash was found by Dr. J. Bell to be present on the average to the small extent of 0*7 per cent. The alkalinity of the soluble ash may be estimated with advantage, the titration being performed with T N ff sulphuric acid, using methyl orange as an indicator ; i cc of T * acid is equivalent to 0-0047 K a O ; the alkalinity of the soluble ash should not fall below i per cent. K 2 O, that from exhausted leaves, according to Dr. Bell, shows on an average only o - 2 per cent, of alkalinity as K 2 O. Caffeine C 8 H 10 N 4 O^ is the alkaloid to which tea owes all its value, it was at one time described as theine, but the identity with the alkaloid of coffee has now been established. Tea is a valuable restorative after fatigue, whether mental or bodily; it is a powerful respiratory stimulant, but unlike cocoa it is not a food. Taken in moderation after a full meal it is not prejudicial to gastric digestion, that is provided it be not too strong and has not been too long intused ; the practice of taking tea with meat meals, so much in vogue in Australasia, is not a good one, as tea under these circumstances is apt to retard digestion ; a cup of tea after a heavy meal, according to Dr. Edward Smith, F.R.S., acts rather as an aid to digestion. The abuse of tea, bringing with it grave nervous and i go dyspeptic symptoms, is no doubt an evil almost comparable with the abuse of alcohol, it is chiefly met with amongst the under-fed or badly-fed women dwelling in large communities such as colliery places or manufacturing centres. COFFEE. Coffee is prepared from the roasted seeds of Coffea Arabica; natural order, Rubiacex. When ground and pro- perly infused it affords a stimulant of great value as a restorative ; it removes the sensation of fatigue, and for those exposed to cold is a most suitable beverage, it does not increase the action of the skin to the same extent as hot tea and alcohol, but increases the heart's action, causing it to beat more quickly and more forcibly. Roasting, which is conducted at a temperature of about 450 F., develops the aroma and flavour of the coffee, and at the same time renders the beans more friable, when roasted, they are ground and ready for use. After coffee has been ground it should be used at once, or else packed in air-tight tins to prevent loss of aroma. Roasted coffee shows amongst other constituents : Per cent. Caffeine ... ... 0-82 to 1-05 Saccharine matter ... 0-41 to 0*43 Fat and Oil ... ... 13-5 Albumen ... ... 11 to 13 Ash ... ... 4-56 to 4-88 Moisture ... ... 0-63 to 1-13 The preparation of the coffee infusion is conducted much better on the continent than in England, -the reason for this lies chiefly in the fact that less water and more coffee is used, and the flavouring is done with caramel instead of chicory ; English people almost invariably use too little coffee; to make good coffee, from i ounce to i^ ounces of coffee should be used with every pint of water. The examination of coffee is conducted with a view to determine the nature and extent of foreign matter added. Chicory is the substance chiefly added ; chicory is the dried and roasted root of the wild endive (Cichorium intibus) which is added to give body and colour, if present in coffee it may be detected by dropping a pinch or two of the sample into some water in a glass, if chicory be present it will be seen to sink almost immediately, leaving the coffee floating for a while on the surface, the particles which sink are soft if they consist of chicory, and hard if composed of coffee, these may be identi- fied with certainty by microscopic examination. With the microscope, chicory shows dotted ducts, which appear as tubes with square ends, also a network of oval or rounded cells ; coffee always shows some of the long spindle- shaped cells met with in the testa or outer covering of the bean, numerous spiral cells found in the raphe, oil globules, starch, and dark angular masses, all contained in cellular tissue, the cells of which are more irregular than those of chicory. The specific gravity of a loper cent, infusion is the usual test upon which a calculation as to the percentages of coffee and chicory present is made. A 10 per cent, decoction is made by placing 10 grammes of the sample in a tared flask and adding dis- tilled water until there is 100 grammes of the mixture, this is boiled for fifteen minutes and the loss made good with water, the decoction is then filtered, cooled to 60 F., and the specific gravity taken ; the specific gravity of a 10 per cent, coffee decoction is, as a rule, 1009*5, and never exceeds 1010*0 at 60 F., whereas a 10 per cent, decoction of chicory shows at the same temperature a specific gravity of 1021 '7. If with a 10 per cent, decoction of a sample we find, for -example, a specific gravity ioi5'6, it will be evident that chicory has been added. Taking ] 009*5 as the specific gravity of a 10 per cent, decoction of coffee, and 1021*7 as that of a similar decoction of chicory, then 1021-7 ~~ IOO 9'5 = I2<2 > and I2'2. represents 100 per cent, chicory; but the sample showed a specific gravity 1015*6, so 1021*7 1015*6 = 6*1, so 12*2 : 6'i :: 100 : x, there is therefore 50 per cent, chicory in the sample. I 9 2 CHAPTER XIII. SPIRITS. Rum continues to form part of the Naval ration for Sea- men and Marines, though no longer issued to Officers. The quantity has been from time to time reduced so that now the non-abstainer only draws a little over 2\ oz. per diem, which is a little less than a glass, or an eighth of a pint of rum,. 4'5 degrees under proof, i.e., spirit containing about 46^9 per cent, by weight of absolute alcohol. Rum is chieflv prepared in the West Indies and Guiana, and is made from the bye-products and refuse sugar juice of the cane sugar industry, the bye-products consisting of the skimmings of the sugar pans and uncrystalizable sugar known as molasses. The best rum is made from the skimmings, the medium quality from a mixture of skimmings and molasses, and the third quality from molasses. After the addition of water and some of the lees of the still to some of the above ingredients, the wash so prepared is placed in the fermenting vat where it remains a week or ten days, during which time fermentation progresses briskly, and after a time a scum rises- to the surface and is removed about twice daily, with the result that at the end of the week or ten days the wort has- become sufficiently attenuated and is fit for distillation, and run into the still. The old method of distilling yielded the best rum, in it the process required two distillations, in the first the distillate was known as "low wines," this on re- distillation yielded the strong rum known as " high wines." Pure rum when first distilled is quite colourless, but storage in sherry casks or the addition of caramel, gives it the ordinary brown colour, the pleasant aroma of rum is due to the presence of butyric ether naturally present.* Well-matured rum is without doubt the most wholesome of spirits, whereas new rum is probably one of the least whole- some, as it is not only very intoxicating but its use is liable to lead to hepatic troubles in cold climates ; no spirit improves with age so much as rum, it loses alcohol, gains cenanthic * A solution of butyric ether in 10 parts of spirits of wine, is sold under the name of essence of pine-apple or Ananas oil, and is much used for. flavouring artificial rum and other spirituous liquors. 193 ether and becomes probably the least harmful of spirituous drinks. (In the year 1865 at Carlisle some rum known to be 140 years old was sold for the enormous sum of 3 35. a bottle.) The Admiralty, mindful of these facts, only issue matured rum to ships, and this is always 4-5 degrees under proof. Per Cent. Alcohol. By Weight. By Volume. British Proof Spirits contain 49 Commercial Cognac 15 u.p. 41 Gin 17 u.p. 40 Rum 15 o.p. 58 *Whiskey 15 o.p. 55 63 The examination of spirits chiefly aims at finding out the amount of alcohol contained and the detection of Fusel Oil (amyl alcohol) and methyl alcohol when present ; these remarks therefore apply equally to all of the above mentioned spirits. The following table shows the average composition of good spirits : Sp. grav. 62 F. Alcohol per cent, by weight Alcohol per cent, by vol. Solids per cent. 1 Ash per cent. Brandy 0*920 to o*934 49- 1 5 to 42-65 56-95 to 50-I5 I'2 0-05 to 0*2 Gin 0-930 to 0-944 44'55 to 3705 52-1510 4475 I'2 O'l Rum 0-874 to 0-926 69-20 to 46-40 76-15 to 54-io ro O'l ** Whiskey 0-915 to 0-920 5 1 '45 to 49' i 5 59-30 to 56-95 trace 0'2 The Sale of Foods and Drugs Amendment Act, 1879, lays down the minimum strength of Brandy, Whiskey and Rum, as * (The Chemistry of Common Life by Johnstone, New Edition, edited by Church. Published by Blackwood and Sons, 1894. ** Adapted from table in Parkes' Hygiene, edited by Notter, 1891. i 9 4 25 degrees under proof, i.e., a Sp. gr. of 0-9474 and 75 per cent. Proof Spirit, which is equivalent to about 35-8 per cent. by weight and 42-8 per cent, by volume of absolute alcohol. Gin is allowed to be still further diluted, viz., 35 degrees under proof, i.e., Sp. gr, of about 0-9563, 30*9 per cent, by weight, and 37-2 per cent, by volume of absolute alcohol. Proof Spirit at 60 F. has a Sp. gr. of 0-9198 and contains 49*25 per cent, by weight and 57-05 per cent, by volume of absolute alcohol, as shown in the Alcohol Tables, q.v. It is often required to reduce a given quantity of spirits ascertained to be a certain number of degrees over proof to proof spirit, or a certain number under proof. The rule is this : Let x = the number of degrees the spirit is over proof. and y be the number of degrees the spirit is required to be made underproof', (if it is required to reduce the spirit to proof then y o). Let n = the amount in volumes of spirit of the ascertained strength which will make 100 volumes of the required strength, and let m = the actual quantity of spirit it is required to dilute. Take the difference between Proof Spirit reckoned as 100 and y, multiply this difference by 100 and divide the result by 100 + x. (100 y) x 100 -- = "" 100 + X. If now we know that "n" Volumes will make, 100 how much will m make. m x 100 number of gallons. n m X 100 of the required strength - - m = the amount of * water which must be added. Example : A sample of rum measuring 90 gallons is 15 o.p. and we require to reduce it to 4*5 u.p., how much water must be added. (100 4-5) X 100 = 83-043 115 83*043 volumes of the sample rum will make 100 volumes of 4*5 u.p. rum, 90 x 100 and 90 gallons will make = 108*377 gallons. and 108-377 90 = 18-377 gallons the amount of water which will have to be added. The Admiralty method of calculating 195 is done in two distinct stages. First the spirit is reduced to proof strength and then from proof strength to the required strength below proof, it is as follows : Multiply the volume of rum in hand by the over proof strength, divide the result by 100, the result added to the amount in hand gives the number of proof gallons required, and the amount of water to be added is obvious. To take the previous example again : go gallons 15 o.p. 90 x 15 = 1350 1350 -4- 100 =. 13*5 (= water to be added). 90 x 13-5 = 103-5 Having reduced the spirit to proof strength, it is required to further dilute it below proof (in this case to 4-5 u.p.). Then the quantity is multiplied by (in this particular case) 4*5 and divided (in this case) by 95'5, and the result thus obtained gives the amount of water required to be acjded to make it the required strength u.p. ">3'5 x 4'5 - = 4^8769 gallons. 95'5 ' ] 3 5 gallons of water had already been added to reduce the spirit to proof strength, so the total added = 18-3769 gallons ; by the first method we obtained 18-377 gallons as the amount required. The amount of alcohol present in a sample is found either by taking a given bulk of the sample at 60 F., then dis- tilling until two-thirds of it have distilled over, then cooling the distillate and adding distilled water until the volume at 60 F. is equal to the original amount taken and then taking the specific gravity and referring to the alcohol tables when the amount of alcohol present is read off ; or else we may determine the amount of alcohol as detailed in Chapter xi. on Lime Juice, by taking the specific gravity of the spirit at 6oF., then evaporating to one-third to drive off the alcohol and adding distilled water in sufficient quantity so that the whole measures at 60 F., the same as it did at first, when the specific gravity is again taken ; the specific gravity before evaporation, subtracted from the specific gravity after evaporation, gives a number which must be deducted from unity (i'ooo), and the value thus obtained, on reference to the alcohol tables, gives the amount of alcohol originally present in the sample. The total solids and ash are determined as in water analysis. Fusel oil is an impurity chiefly met with in whiskey, and 196 gin, but may be found in cheap brandy and spirits made from potato, beet-root or corn spirits ; it is a mixture of several homologous alcohols, the greater part of it can be isolated by fractional distillation, though after this, traces are still apt to remain, and are recovered with difficulty. Fusel Oil is chiefly composed of amyl-alcohol C,, H 12 O, which has a specific gravity of 0-817, and a boiling point of 132 C (the boiling point of ethyl alcohol being 78-4 C), and is recognisable by a peculiar penetrating smell. Fusel oil from potatoes consists chiefly of iso-amyl alcohol, and often contains iso-butyl alcohol and decoic acids. Fusel oil is much more poisonous than ethyl alcohol, and the maturing of whiskey and other spirits containing fusel oil causes the amyl-alcohol to split up into other bodies less irritating, this alteration in composition improves the flavour and causes the whiskey to become mellowed. If a spirit con- tains fusel oil in an appreciable quantity, it may be detected by pouring a little of it on the hand, rubbing the hands together and allowing the more volatile ethylic-alcohol to evaporate, then if fusel oil be present, a pungent suffocating smell is experienced when the hands are held over the mouth and nostrils. Another test is to take some of the suspected spirit (100 cc), distil at a temperature of about 78*4 C. to remove the ethyl-alcohol, then, to the residue in the flask when cool, add some ether and lastly some water, remove the ether layer and allow it to evaporate spontaneously, and to one portion of the residue add (i) two parts of acetate of potash and one part of strong sulphuric acid, when an odour of essence of jargonelle will be evolved, if fusel oil be present. To the other portion of the residue add (2) a little bichromate of potash and twice its bulk of strong sulphuric acid, when green oxide of chromium will be be formed if fusel oil be present. For the quantitative estimation of fusel oil and the methods for detecting methylic alcohol, the reader is referred to such w r orks as Allen's Commercial Organic Analysis, or the work on Food and Drugs by Pearmain and Moor. BEER AND STOUT. Beer and Stout are issued to convalescent patients in Naval Hospitals, but these articles do not enter into the ordinary service dietary. In hospital, complaints are not un- frequently made as to the quality of the beer, which on investigation often prove groundless ; it is therefore a matter of importance lor Naval Medical Officers to be able to form 197 an opinion as to the fitness or otherwise of the beer or stout supplied. Beer is a fermented malt liquor flavoured with hops or other vegetable bitter and containing amounts of alcohol vary- ing from i to 10 parts by weight per cent, thus : - Small Beer contains from i to i'5per cent., by weight of Alcohol Porter ,, ,, 3iU>5i Brown Stout ,, 5^ to 6 ,, ,, Bitter and Strong Ales 5^ to 10 Ordinary Bitter Ale or Mild Burton show about 6 per cent, by volume of alcohol. Allsopp's Pale Ale about 6*4 per cent, by weight, or 8 per cent, volume. Guinness Stout XX about 5 per cent, by weight, or 6 per cent, by volume. Lager beers an average amount of about 4 per cent, by weight, or 5 per cent, by volume. Bavarian beers about 2 per cent, by weight, or 3 per cent by volunfe. English beer differs from German beer in being less aerated and containing rather more alcohol, in its preparation the fermentation is conducted at a higher temperature, and more rapidly, by means of high or surface fermentation ; the low or bottom fermenta- tion, produced by a different variety of yeast being employed in the production of the Lager or German beers. The Burton beers owe their flavour largely, to the w r ater of that place con- taining a considerable amount of calcium sulphate ( 18-96 grains per gallon) and total sulphates, including sulphates of potash, calcium and magnesium equal to ig'8 grains per gallon of SO 3 . Examination of Beer. Beer should be clear and bright, that is to say show no turbidity, the smell should be agreeable, and the taste free from acidity and not persistently bitter. If turbid it will finerally be sour, and if very acid show the Mycodermaaceti. he specific gravity, at 60 F. of English beer, is usually frOm roio to roi4- Porter and stout show a higher specific gravity, viz. : about ro24, whereas the German Pilsener is usually roi3- The alcohol may be determined as described under Spirits or by Tabarie's method, in which the specific gravity is taken at 60 F. after which a definite quantity (iooori5occ) is boiled down to one third, and then made up to the original volume at 60 F with distilled water, when the specific gravity is once more taken, the amount of alcohol is then found by dividing the first specific gravity before boiling, by the second specific gravity obtained as detailed, and the quotient referred to the alcohol table on p. 202. Acidity is divided into fixed ^and volatile, the fixed is due to non-volatile acids, chiefly lactic, but there may also be other acids such as succinic, tannic, or malic; the volatile are acetic and carbonic acids. The total acidity is determined by taking 20 cc of the beer, diluting with water and titrating with , sodium hydrate, using litmus as an indicator, each i cc of , sodium hydrate is equivalent to 0-005958 (in round numbers *oo6) grammes of acetic acid (HC 2 H ? O 2 ) acidity thus found is expressed in terms percent, of acetic acid (HC., H 3 OJ. Fixed acidity is found by taking 20 cc of beer, diluting to 100 cc and evaporating down to 50 cc, on titrating with , N sodium hydrate as before, we find the percentage amount of fixed acidity expressed as lactic acid i cc of the ^ sodium hydrate being equal to 0^009 grammesof lacticacid(HC 3 H S O 3 ). The volatile acidity is found by taking the difference be- tween the number of cc used when taking the total zx\& fixed acidities, and multiplying the difference by 0006, in order to express it in terms of acetic acid (HC a H 8 O a ) and calculating to percentage. The total acidity or good beer should not exceed 0*35 per cent., and will usually be about o - 2, and that of porter should not exceed 0-28 per cent., and as a rule will be found to be about o - 2 per cent., expressed as acetic acids. Malt Extract : Beer evaporated to dryness yields (< malt- extract," consisting ot soluble substances trom the hop, unde~ composed sugar, gluten from the grain, and a small amount of glycerine and mineral matter ; in estimating the extract, 5 cc is evaporated to dryness over a water bath in a platinum dish, and finally in a water oven until the weight is constant, the amount varies as a rule between 4^ and 8 per cent. In old Scotch ales it is more than in ordinary ale, and in stout it is usually about 6 or 7 per cent. The ash is obtained by in- cinerating the extract, and amounts as a rule to 0-3 or o - 4 per cent. It is unlikely that strychnine would be met with except in attempts at poisoning, the allegations at one time made on the Continent in regard to the use ot strychnine in English Beer have long since been disproved ; for the detection of this and such substances as picrotoxine, picric acid, &c., the reader is referred to such works as " Toxicology," by Wood- man & Tidy ; or ." Foods, their Composition and Analysis," by Wynter Blyth ; or the work on " Poisons, their Effects and Detection," by the same author. Boric and salicylic acids are often employed with beer by brewers. Boric acid is detected as detailed in the chapter on. Milk. 199 If present, salicylic acid can be readily detected by taking about 150 or 200 cc, evaporating down to J over a water bath, and when cool extracting with ether, the salicylic acid is taken up by the ether, and on the evaporation of the ether, ferric chloride, (Fe a C1 6 ) gives the characteristic violet reaction. WINES. Wines are the result of the natural fermentation of grape- juice, that is to say they are fermented without the addition of yeast as is the case with malt liquors. Wines are characterised by the presence of tartaric acid, and they also contain acetic acid, though to a less extent. In the production of wine, the grapes are gathered when ripe and placed in wooden troughs, where they are first pressed by the feet, and then by a screw-press ; when crushing grapes in the sherry wine-presses the men wear wooden clogs with nails on the soles and heels ; the reason for this primitive method is that the weight of the average man is just sufficient to express the juice without injury to the skins or branches of the grapes, which if pressed too much would yield bitter substances and ruin the wine, when the first juice is expressed, the crushed grape skins, are in Spain sprinkled with " yeso " a natural earth composed principally of calcium sulphate, the amount of " yeso " employed being a little over a kilogramme to a load of grapes weighing 812 kilogrammes, the addition of calcium sulphate, which is deprecated by many, is said to cause the crushed skins to mass together, clear the wine, aid the maturing process and assist in the formation of the various volatile ethers, which produce the aroma or "bouquet" of a wine. According to many the addition of calcium sulphate gives rise to the formation of free sulphuric acid, but this is not so, what occurs is represented as shown in the. Lancet for 29th Octo- ber, 1898, by the following equation: 2KH C 4 H 4 6 + Ca SO 4 = K 2 SO 4 + Ca C 4 H 4 O 6 + H. C 4 H 4 0. that is to say potassium acid tartrate is converted into insoluble tartrate of lime, which is precipitated, and free tartaric acid remains in the wine, it is on account of the presence of free tartaric acid that sherry was adopted in pharmacy as a solvent of iron and certain active principles of drugs. The potassium sulphate shown as a result of the addition of calcium sulphate, has been thought, by M. Lancereaux, to be the cause of the large amount of atrophic cirrhosis met with amongst wine- drinkers, but the evidence in support of this view is not forth- 20O coming, and it is much more probable that it is the alcohol which is responsible for the pathological condition referred to. In regard to acidity a certain amount of acidity renders wine palatable, champagne is the least acid, next to it come marsala, port, and sherry ; clarets and Rhine wines, as a rule, contain the most acid. The percentage composition of a few wines is as follows : Name of Wine Alcohol by weight Solids Sugar Fixed acid as Tartaric Volatile as Acetic Champagne 7'9 . I2'4 io'6 0-30 Port l8- 5 4'2 r6 0-25 03 Sherry 13-98 1-82 ! 0-197 0'35 II 3 (amontillado) Sherry i6'22 8-865 3-85 4 I2 126 .(oloroso) Marsala 17-5 5*4 3-2 0-32 Madeira 16-7 5' 2'I '54 Claret (St. Julien) 9-8 2-7 0-3 0-51 0-14 Wines, especially Port, Sherry, Madeira, are greatly improved by age, the "bouquet" improves chiefly as a result of etherification ; the "vinosity" also greatly improves with age, the vinous odour of wine is due to an infinitesimally small amount of oenanthic ether, which appears to increase by being kept. A wine is described as dry when most of the sugar (glucose) has been converted into alcohol, and fruity when an appreciable amount of sugar still remains. Examination of wine Specific gravity is taken at 60 F preferably with a Westphal's balance. Alcohol may be esti- mated as described under beer. Extract is determined in a similar manner to that of beer, and the ash by ignition of the of the dried extract. Acidity divided into fixed and volatile, is found by first finding the total acidity, by taking 20 cc of wine, diluting with water, and titrating with ^ Na HO using phenolphthalein, as an indicator and noting the number of cc * Na HO used. Fixed acidity is found by diluting 20 cc of the wine with 80 cc of distilled water and boiling down to a third, then making up to the original volume with distilled water and titrating with * ( Na HO and phenolphthalein, the number of cc ,* Na HO used multiplied by 0*0075 gives the amount of fixed acidity as tartaric acid (H 2 C 4 H 4 O a ) in 20 cc this is then calculated to 201 per centage. The difference in the number of cc ^ Na HO used in determining the total and fixed acidities, multiplied by 0-006 gives the volatile acidity in 20 cc expressed as acetic HC 2 H 3 O a this is then calculated to percentage. The arti- ficial colouring matters most often employed, are logwood, cochineal, fuchsine, and magenta. The method employed by Dr. Dupre for the detection ot artificial colouring is a useful one, it is conducted as follows A 10 per cent, solution of good, clear gelatine is made, and allowed to set in a mould, after which it is cut up into little cubes f-in. square. Several of these are soaked in the wine for 24 hours, after which they are removed, washed in cold distilled water and cut into ; in natural wine the colour does not penetrate for more than i' ti inch, whereas the stains mentioned above will penetrate nearly if not quite to the centre. Another test, described by Pearmain and Moor, is to add ammonium hydrate to some of the suspected wine until it is alkaline in reaction, after which a little ammonium sul- phide is added, and the liquid filtered. If the wine be genuine the filtrate will be of a greenish colour, if artificially coloured it will be some other colour, such as red, violet, brown, &c. In the Paris Laboratory several preliminary tests are emp'oyed to detect artificial colouring. In one of these tests, sticks of chalk steeped in a 10 per cent, solution of egg-albumen are dried first in the air and then at iooC ; excess of albumen is removed from the chalk by scraping, after which two or three drops of wine are allowed to fall on the chalk, natural wine gives a gray colour, or perhaps a bluish tint if the wine be young, out green, violet, or rose, if artificial. Another French test is to add baryta-water to the wine until it is of a greenish hue, and then shake it up with acetic ether or amylic alcohol, pure wine shows no colour in the upper layer, either with or without the addition of acetic acid. If basic coal-tar colours are present, the solvent is coloured according to the nature of the dye, examples of which are fuchsine, mauvene, amidobenzene, &c.* Preservatives, such as Boric and Salicylic Acids are often added to wine and may be detected as described in previous chapters. * Foods Composition and Analysis, P. 500, 3rd Edition, A. W Blyth. 202 ALCOHOL TABLES. ?uao aad j CM co yi M ONO ON ON b M M CM jooa c i MVO -<4-MOO ^J-M !U9o a9d umioA A"q loitooiv 9-jniosqv 8vo o 100 inioioo o o fOt>.M <7>^fOt^CMvO O\ ciocbcb ovoicrib b M M M N ^j vo *o o o o vo c^- 1^ t^ t^ t^ t^^ c^* ia..> add " O O O u~iO lOiOiOO vOiOO O O u-)iou-)iOiOO O O u~)iOO voO ^OO lOO OO >OO O m t^ M in o ^oo N r^ M 10 o ^t-oo CM vo o o Oi ^-oo cs o o 1000 m t^ w in o rt-oo CM t^ M a 'Sap 09 ogioads O -^- 1^1 CM M O CTiOO t^O lO ^- fO N M COCOCOCOOOCOOOCX3000000COOOCOCOOOCOOOCOOOOOOOCOCOCOOO IO ^ fO N M fjuao aad ^"jdS jooaj CO t^-O iO T en N M o I OO I ONCO I>-O to T m CM M O ONOO t^O to T ro O CMCMCMCMCMCMCMCMCM | ON! MMMMMMMMMMQOOOOOOOOO ON ON ON ON ON ON ON ON ON ON ON ON ONOO CO 00 00 ONONONONOlONONON ON. I i-> I ONO\ONONC>pNONONpNON 1^1 fjuao jad jbojd 1>CMO O fOOCO M TioO l^O O TO I s * ON O M CM O ON ONCO O T en I s -. ON O >O iOO quao aad | 9uuii JA Xq i iOOOOO O ONO rj- M iOCMOO T O M i-i CM iOOOO>OOOiOi CO ^-pOOOMOH u~iO t^ t>.OC Co CM t^ M t^ T IO iO iO tO to IO O lOiOO iOO O tO (^^-MCO ^-M t^cnO IOM t^ IOO K Kcb ONOiO M M CM CM CM CM CM CM CM CM CM rornro<^f^ tOtoO O O O O O iO"->O iOO tOtOO tOtOOtOtOiOtOO O OO IOM t^r*"(CO TO iOO IOMO NO M t^-MO MO MO MO M ~>O iO IOO O O M TtOONM CMO PNCMO M tOpNTO tOM t^voOOOO rOMOO tOtOOO CM pNO W^p fn b b CM on TO t^ob ON M CM T too oo b M rn TVO cb ON M co too cb b N rn too cb b M rn MMMMMMCMCMCMCMCMCMCMrnrOmrnrnTTTTTTiOtOtO iOOOOOtOO>OOiOOOtOiOOiOOOOOOOOOOiOiOOOiOiOiO>OtO( O en O I s * to M OiO TMOCOOtOTrnCMMMOOOOpOpNppNpN |>cp t^-^p Y^ " bbMCMCMcnTT too i^cb cb b\ b M CM rn T >oo Kcb ON b M M rn rn T ioo Kcb ON b^ iOiOOtOiOOO 8iOiOOiOiOOCOtOiOOOOOOO H O^CO M CM rnrnTtOO f^ t^OO ON O M M CM rn T I -39p 09 W ' oyioadg 203 APPENDIX. METRICAL WEIGHTS AND MEASURES. '3937 English inches 0*39371 ,, 3'9378 39'37079 393'779 109-3633 English yards 1093-6330 ,, (a) LENGTH Millimetre Centimetre = Decimetre = Metre Decametre Hectometre = Kilometre =: Myriametre = (b) AREA. Centiare or square metre 10-764 square feet Are or 100 square metres 1076-429 Hectare or 10,000 square metres = 107642*993 ,, 100 Hectares = i square kilometre = 247 acres (c) CAPACITY. i Millilitre or cubic centimetre = 0*061 cubic inch, i Litre or cubic decimetre = 1000 cubic centimetres = 1-76077 pint. (d) WEIGHT. 0-01543 English grains 0-I5432 1-5432 tW_ i Milligramme i Centigramme i Decigramme 1 Gramme 15' i Kilogramme = 1000 grammes = 2*2 Ib. avoirdupois To convert millimetres to inches ,, centimetres ,, decimetres ,, ,, 'metres inches multiply by to millimetres ,, ,, to centimetres ,, ,, to decimetres ,, ,, to metres Milligrammes per 100 cc = parts per 100,000 Centigrammes per 1000 cc = parts per 100,000 0-03937 0-39371 3-93708 39'37079 25-4 2 '54 0-254 0*0254 204 To reduce grammes to grains multiply by 15*432 ,, grains to grammes ,, 0*0648 ,, ounces to grammes 28*349 ,, kilogrammes to pounds ,, 2*2046 ,, pints to litres ,, 0*5676 pints to cubic centimetres 567*936 ' ,, gallons to litres ,, 4'54 r litres to gallons 0*22 RELATIONS OF MEASURES AND WEIGHTS. i cubic inch of distilled water at 62 F. and 30 inch barom, = 252-458 grains. i fluid ounci; is the measure of i ounce or 437-5 grains of water. i pint is the measure of 1*25 Ib. or 8750*0 grains of water. i gallon is the measure of 10 Ibs. or 70,000 grains of water. CO-EFFICIENTS REQUIRED IN VOLUMETRIC ANALYSIS, DECI-NORMAL ACID SOLUTION. Oxalic Acid ... ... .. 0-0063 Sulphuric Acid ... ... ... 0*0049 Baryta (Ba(HO), ... ... ... 0*00855, Caustic Potash (KHO) ... ... ... 0*0056 Caustic Soda (NaHO) . . ... 0*004 DECI-NORMAL SODA SOLUTION. Caustic Soda (NaHO) ... ... ... 0*004 Acetic Acid (H C 4 H O ft ) ... ... 0*006 Tartaric Acid (H 4 C 4 H 4 O fl ) ... ... 0*0075 Lactic Acid (H C, H 5 O 3 ) ... ... 0*009^ Oxalic Acid (H, C 2 ti 4 2 H, O) ... ... 0*0063 Hydrochloric Acid(HCl) .".. ... 0-00365 Sulphuric Acid (H 8 SO 4 ) ... ... 0*0049 DECI-NORMAL SOLUTION OF NITRATE OF SILVER. Argentic Nitrate ... ... ... 0*016869 Chlorine (Cl) ... .. ... 0*003519 Sodium Chloride ... ... ... 0*005807 DECI-NORMAL IODINE SOLUTION. Iodine .. .. ... ... 0*01259 PAVY'S SOLUTION. 100 cc = 0*05 gramme glucose. TOO cc = 0*0962 gramme lactose. 205 FEHLING'S STANDARD SOLUTION OF COPPER. (Two SOLUTIONS). No. i consists of 34*64 grammes of cupric sulphate dis- solved in water with the aid of 0*5 cc of strong sulphuric acid, and diluted to 500 cc. No. 2 is made by dissolving sodium hydrate 77 grammes ; tartarated soda 176 grammes; distilled water sufficient to make the whole measure 500 cc. When required for use No. i and No. 2 are used in equal parts, and 10 cc of the mixture are equivalent to : Glucose ... ... 0*050 gramme Maltose ... ... 0-0807 Lactose ... ... 0-0678 ,, Inverted Cane Sugar ... '475 > Inverted Starch ... ... O"O45 o LIST OF THE ATOMIC WEIGHTS OF THE CHIEF ELEMENTS IN COMMON USE IN ANALYTICAL WORK. True Atomic Approximate Weight Atomic Weight Aluminium ... 26^90 27*0 Antimony ... 119-00 119-0 Arsenic ... 74'5 75' Barium ... 136*40 I 37' Bismuth ... 207-30 207*5 Boron ... 10*85 ll ' Bromine ... 79'35 79' Calcium ... 39' 7 l 4' Carbon ... 11-91 12*0 Chlorine ... 35-19 35-5 Chromium 5i'74 52'O Copper ... 63-12 63-0 Gold ... I 95'7 196*0 Hydrogen .... roo ro Iodine ... 125-90 127*0 Iron ... 55'6o 56-0 Lead ... 205-35 205-5 Magnesium ... 24-18 24*0 Mercury ... 198*80 199*0 Nitrogen ... I3'94 1 4' Oxygen ... 15-88 i6'0 Phosphorus ... 30*80 31 Potassium ... 3^'^3 39'o Silver ... 107*11 107*0 Sodium ... 22'8S 23-0 Sulphur ... 3 r '82 32*0 Zinc ... 64*91 65*0 INDEX TO PART II. PAGE Acidity of beer . . . . 198 ,, ,, bread . . . . 178 ,, ,, lime-juice .. .. 183 ,, wine . . ... 200 Acids in peaty water . . . . 70 Actinophrys, fig. . . . . 29 Adams' method for milk fat . . .. 141 Added water in milk . . 142 After-damp .. .. 123 Agrostemma githago . . 167 Air, bacteriological examination of .. 131 ,, composition of .. .. 115 ,, examination of .. .. 117 ,, respired, town and country .. 115 Albuminoid ammonia . . . . 82 Alcohol, estimation of . . 195 ,, tables .. .. 202 Alum in bread . . . . 178 ,, ,, test for . . .. 179 Aluminium process for nitrates .. , 90 Ammonia, free and albuminoid . . 82 Amphioteric reaction of milk .. 134 Anguillulo2 tritici .. .. 165 , , water . . . . 70 Angus Smith, test for air .. 123 Annuloida . . . . 70 Annulosa . . . . 70 Anthrax in milk .. .. 151 Anti-incrustators . . . . 79 Arthopoda . . . . 70 Ash , reaction of bread .. .. 178 Asboths' method for butter . . 158 Aspergillus glaucus .. .. 177 Atomic weights . . . . 205 Bacilli and lead . . . . 100 Bacteriological examination of air . . 131 ,, ,, milk .. 147 ,, ,, water .. 103 Balance, Westphal's .. .. 113 Baryta test for colours in wine . . 201 Beaume's hydrometers .. .. 114 Beer . . . . 196 199 Biscuit .. 180 181 208 Boracic or Boric Acid, effects of . . 153 ,, ,, ,, in beer . . 198 in butter . . 162 ,, ,. ,, in milk . . 152 ,, ,, ,, in wine . . 201 Boyle's law .. . . 119 Branchipus stagnalis, fig. 29 Bread . . . . . . 176 ,, acidity of .. 178 ,, alum in . . . . 179 Bunt . . . . 164 Burton water . . . . 197 Butter, composition of . . 155 ,, fat .. .. 156 161 Butyric ether . . . . 192 Carbonic acid .. .. 117 123 oxide .. .. 123 Centrifugal machines .. .. 137 140 Charles' law . . . . 119 Chicory . . . . .. 190 191 Chocolate .. .. 185 Choke-damp .. .. 125 Chlorine in water . . . . 76 Cholera and milk . . . . 152 ,, ,, water .. .. 106 Cirrhosis and wine . . . . 199 Citric acid in lime-juice . . 183 Clearness of water . . . . 68' Cocoa . . . . 185 Co-efficients required in volumetric analysis . . 204 Coffee .. .. 190 Coli bacillus, characters of . . 108 Colorimetric estimation of nitrates . . 92 Colostrum . . . . 134 Colouring matters in butter . . 156 ,, rum .. .. 192 ,, wine . . 201 Colour of water . . . . 68 Contracts, bread .. .. 176 milk .. -.153 154 Copper in bread . . . . 180 Corn-cockle . . . . 167 Correction for pressure and temperature 119 Cotton .. .. ..102 Cows' milk . . . . 133 Curd in butter . . . . 156 Cyclops . . 70 Darnel grass . . . . 167 Deci-normal solutions . . 204 Diarrho3a of infants caused by milk .. 152 Diphtheria and milk .. 151 Diseases spread by milk . . . . 146 Ear-cockle or vibrio tritici . . 165 Eisner and typhoid fever bacillus . . 107 Ergot in flour . . . . 167 20Q PAGE Expired air . . . . 115 Estimation of CO., .. .. 117 Endiometer . . . . 127 Euglena . . . . 70 Ewe's milk . . . . 133 Examination of the air of rooms .. 117 Facing of tea . . . . 188 Fat in cocoa . . . . 187 Fatty acids in butter . . . . 155 estimation of .. 157 Fehling's solution . . . . 205 Filtering of water . . . . 109 Fixed hardness in water . . . . 81 Flour, composition of, etc. . . 165 Foot and mouth disease (milk) . . 148 Forchammer process . . 96 Formalin in milk . . . . 152 Fusel oil . . . . 195 196 Garget and milk .. .. 151 Gas burette, Hempel's . . 227 Gases, detection of, in air . . 129 Gerber centrifugal apparatus . . 139 Gill, method for estimation of CO 2 , by Dr. . . 120 Gin . . . . 193 Globules, milk . . . . 134 Goats' milk . . . . 133 Gluten . . . . .. 165 167 Gravity of beers . . . . 197 ,, ,, chicory . . . . 191 ,, ,, coffee infusion .. 191 ,, ,, lime-juice . . . . 183 ,, milk . . . . 134 Griess' test for nitrites in water . . 95 Hair . . . . 102 Hardness of water . . . . 77 Hehner's test for formalin . . 152 Hempel's absorption pipette .. .. 127 Hendon disease . . . . 149 Hesse's apparatus .. .. 131 Hessian fly and rust in wheat . . 163 Hubl's method for fats . . . . 161 Hydra vulgaris, y/g. .. 29 Ilosvay's test for nitrites . . . . 96 Indol reaction . . . . 106 Inferences from Wanklyn's process . . 89 Iodine test for fats . . . . 160 161 Iron in water . . . . 69 Kjeldahl's process for the estimation of nitrogen 144 Lactose, estimation of . . . . 142 Lead in flour . . . . 166 water 100 210 Lead, tests for . . . . 73 Leaves substituted for tea .. .. 188 Leeches . . . . 70 Leffman-Beam apparatus .. .. 137 Lime-juice .. .. 182 184 Logwood test for alum .. .. 179 Lolium in flour . . . . 167 Loss in weight of bread . . . . 176 Lunge and Zeckendorff s method for CO., 120 Lustre of water . . . . 68 Maize and disease . . . . 167 Maize starch .. .. 173 Margarine . . . . 155 157 161 Marsh gas .. .. 115 McWeeney on boric acid . . 153 Meal mites . . . . 166 Melting point of butter . . 156 Mermet's test for CO . . . . 124 Metric system of weights and measures . . in Mice as indicators of air .. .. 125 Miguel's scale for bacteria in water . . 105 Milk, composition of .. .. 133 Milk, standard of cows' . . 135 Milk, sugar estimation of . . 142 Minerals added to flour . . 66 Mines, precautions against the air of . . 125 Monas . . . . 70 Moulds in bread .. .. 177 Mucor mucedo .. .. 177 Navy ordinary chocolate . . . . 187 ,, soluble ,, .. 187 Nessler solution . . . . 84 Nitrates, estimation of . . 89 Nitrites . . . . . 95 Normal solutions . . . . 14 Oat starch .. .. 173 Organic matter in air, estimation of 125 water . . . . 74 Oxidisable matter in water . . 96 Oxygen in air, estimation of . . . . 127 Paramecium . . . . 70 Parietti method of, for detection of typhoid fever bacillus 107 Pathogenic microbes in water . . 106 Pavy's solution . . . . 204 Peat in water . . . . 70 Pellagra and maize . . . . 167 Pettenkofer's process for estimating CO 2 117 Phosphates in water . . . . 72 Physical characters of milk . . 134 Plastering of wines, vide Yeso . . 199 Plumbism and water . . 100 Polytoma.. .. .. 70 Potash salts in the blood . . 182 211 PAGE Potatoes, effect of, on bread .. .. 178 Potato starch .. .. 171 Preservatives, effects of .. .. 153 in beer . . 198 ,, butter . . . . 162 ,, ,, milk . . 152 ,, wine . . .. 201 Proof spirit . . . . 193 Puccinia graminis . . . . 163 Pyrocollodion powder .. 123 Qualitative tests for water . . . . 71 Reaction of water . . . . 70 Reducing strength of spirit . . 194 195 Reichert process for butter- fat .. 157 Respiratory impurity, limit of .. 116 Respired air . . . . 115 Rhizopoda . . . . 70 Rice starch . . . . . . 174 Richmond on added water in milk . . 143 Richmond's milk slide rule .. .. 139 Rotifera . . . . 70 Rum . . . . . . 192 Rust in wheat . . . . 163 Salicylic acid in beer . . . . 199 ,, ,, butter .. 162 ,, milk .. .. 153 wine .. 201 Saline ammonia . . . . 82 Salt in butter . . . . 156 Scarlet fever and milk . . . . 149 Scurvy rmd sterilsied milk . . 147 Scurvy . . . . 182 Sediment of water . . . . 69 Sewage farms and milk . . . . 151 Silk .. .. 102 Smell of water . , . . . 69 Smith, Angus, method for estimation of CO 2 123 Smut in wheat . . . . 165 Sodium salts in the blood .. 182 Soft waters . . . . 79 Solids in water . . . . 75 Specific gravity .. .. 112 ,, corrections .. 136 Spectroscopic test for CO .. .. 124 Spirits . . . . 192 Spirits, strength of . . . . 193 Spring waters .. .. 71 Starch granules, various .. .. 168 175 Stentor . . . . 70 Sterilised milk . . . . 147 Stokes, colorimeter . . . . 94 Stout .. .. .. 197 Sulphates in beer . . . . 197 sherry .. .. 199 212 PAGE Tabarie's method for estimating alcohol 197 Table for correction of sp. gravity . . 136 alcohol .. .. 202 Taste of water . . . . 68 Tea .. .. 188 Theobromine . . . . 187 Tilletia caries . . . . 164 Tuberculosis and milk . . . . 146 Typhoid fever and milk . . 146 Uredo faetida " bunt " . . . . 164 ,, segetum " smut " .. 165 Verdet in maize . . . . 168 Vibrio tritici .. .. 165 Vogel's test for CO . . . . 124 Von Asboth's method for butter . . 159 Wanklyn process . . . . 82 Water-gas .. .. 124 Water examination . . . . '67 Water in butter . . . . 156 Weevil . . . . . . 165 Weights, atomic . . . . 205 ,, metric . . . * 203 Werner- Schmidt process for milk fat . . 140 Westphal's balance .. .. 113 Wheat .. .. 163 ,, diseases .. .. 163 164 Whiskey .. .. 193 Wines .. .. .. 199 201 ,, artificial colouring of .. 201 ,, plastering of, vide Yeso .. .. 199 Wool .. .. 102 Yeso .. .. .. 199 Ziehl-Neelsen's stain . . 106 Zinc, tests for . . 73 FART III. METEOROLOGY. 2I 3 PART III, CHAPTER I. BAROMETRIC PRESSURE. That the air has weight is a matter of common observa- tion, for we know that bodies whose supporting walls are slender can remain apart if full of air, but collapse when empty; again we know that an air-tight box can be exhausted of air, and that when so exhausted weighs less than when full, the difference in weight denoting the weight of the air contained. At 29-92 inches and 32 F. a cubic foot of air weighs 573*5 grains, at 30^00 inches and 60 F., 534^47 grains. The weight of the atmosphere at sea-level exerts a pressure of i4'64 Ibs. on the square inch when the mercurial barometer stands at 29*92 inches or 14*73 Ibs. a ^ 3 inches. Bulk for bulk air is 760 times lighter than water. Air is considered by Lord Kelvin to consist of a large number of molecular particles, so minute that 500 millions of them placed in contact would only occupy a line i inch in length. The rate at which these particles vibrate depends on their temperature, and the amplitude of these vibrations is also dependent on temperature, so that gases are said to expand in a regular manner, viz., ub of their volume for each i C. Consequently a volume of gas which occupies T cubic inch at o C. would occupy 273 cubic inches at 273 C., or theoretically nothing at 273 C., but we know that long before that temperature could be reached the vibration of the particles would be insufficient to prevent cohesion and show, firstly, the property of liquids, and lastly, the substances would become rigid, i.e., solid. Charles' law enunciates, that provided the pressure be constant, the volume is proportional to its absolute temperature. Boyle's law states, that with a constant temperature the volume varies inversely with the pressure. Barometers are instruments devised for measuring the weight of the atmosphere ; this is done either by indicating by the height of a column of fluid which the air is capable of 214 supporting, or by indicating the pressure by means of springs and an exhausted metallic box as with an aneroid barometer. The height of the column shown in fluid barometers is inversely proportional to the density of the fluid. Mercury is the com- monest fluid employed, and in its simplest form a mercurial barometer consists of a tube about 34 inches in length, closed at one extremity, filled with mercury, and then immersed in a vessel containing mercury, taking care to prevent the intro- duction of air ; under ordinary circumstances the mercury will fall to a height of about 30 inches, and the space above the mercury in the tube will only contain a little mercury vapour, this is in fact almost a perfect vacuum, and is known as the Torricellian vacuum. The ordinary range of baro- metric pressure at the sea-level is between 28 inches and 30*5 inches, but a height of 3i'2y inches has been registered, and one so low as 27-124 inches, the scales of barometers are there- fore marked off between 27 inches and 32 inches. The scale being liable to alteration in length with variations of tempera- ture, all the best barometers have the scale marked off on brass, because the co-efficient of expansion of brass is well- known. If wood were employed this would be uncertain, as different woods expand to different extents. It will readily occur to anyone that if we lay off the scale of a barometer at any particular time, the scale will be correct for that time, and on any subsequent occasion when the pressure may be the same, but not for any other pressure, because the level of the mercury in the cistern must vary when the mercury rises or falls in the tube. Various methods have been devised for obviating this source of error. It can be met by : (i). A barometer with a pliable base to its cistern, as in Fortin's barometer, so arranged that the level in the cistern may be always brought to the same point before taking a reading. (2). By employing a contracted scale, as in the Kew marine barometer, in which the inches are not true inches, but shortened to an extent, varying with the ratio of the sectional area of the cistern to the sectional area of the tube. (3)- By employing a Syphon barometer, in which the true reading is the difference between the heights of the fluid in the two arms of a U tube with arms of different length, one arm (the longer) is closed at the top, whereas the shorter one is open, (4). By a capacity correction. Fortin's barometer has the lower end of its cistern made of boxwood and the upper part of glass, so that the level of 215 -32 Fig. 55 the mercury in the cistern may be seen ; the bottom is closed by buckskin, and the top by a brass lid from which depends an ivory pointer, the tip of which is called the fiducial point ; at the bottom of the case enclosing the cistern is an orifice through which passes a screw which presses on a wooden button against the buckskin. To set the instrument the screw is turned so that the level of the mercury is raised until it reaches the fiducial point. A reading is taken, and then the screw turned down so that the mercury is no longer in contact with the pointer. The scale is marked in true inches, sub-divided into OT and 0*05 of an inch. This barometer, like other fluid barometers, cannot be accurately read nearer than 0*05 of an inch without the aid of a vernier. The vernier is a Fig. 56 sliding scale divided intodivisions, so that n division of vernier n-\- or i division of the fixed scale. The ordinary vernier has 25 div- visions, which are equal to 24 of the fixed scale, each of which is 05 inchesapart, onedivision of the vernier is therefore smaller than one division of the fixed scale by A of -05 inches, or expressed in decimals, 0-04 x '05 = o - oo2 inches. To read the barometer with a vernier, the bottom of the vernier must be brought down so that its lower end forms a tangent to the meniscus of the column of mercury in the tube, and the eye must be exactly in the same straight line with the bottom of VERNIER the vernier, then notice where one division of the vernier corresponds Bavonutev with one division of the fixed ,- ^,- s case scale, this can of course only be a.tis29-946in.) one point, except in the case where top and bottom both correspond to a line on the scale, and then the reading is obvious. We therefore count up the num- ber of divisions from the bottom of the 30 -29 2l6 vernier, where a line of the vernier corresponds with one of the fixed scale and add this amount on to the reading of the fixed scale ; thus, supposing the scale reading showed 29*15 inches, and the sixth line of the vernier coincides with a line on the scale, then our reading will be 29*15 -f (6 x -002) = 29' 162. The special features of the Kew marine barometer are: ( i ) . That the bore of the tube for the greater part of its extent is narrowed, so as to avoid the pumping and sucking action of the mercury which occurs in a wide tube as a result of the motion from side to side, which must, to a certain extent, occur ^^ on board ship despite the precautions taken in the c BUSS wa y the barometer is slung. (2). In order to prevent the ingress of air or m| moisture, a pipette, known as Gay Lussac's pipette, (A.B. Fig. 57) is inserted in the course of the tube, this is introduced in such a way that air or moisture g a i n i n & access to the tube lodges at the point marked A in the figure, and so is prevented from reaching the torricellian vacuum. (3). The cistern is made of iron, because iron is not acted upon by mercury, and it has a small H I opening at its upper part guarded by a leather dia- g 3 IE phragm which allows the air pressure to act but I' prevents any escape of the mercury. (4). But the special feature of the Kew marine barometer is the contracted scale, in this the - f$l i ncnes are not true inches, but each is 0.04 less than a true inch, the 0*04 being the ratio of the sectional area of the cistern to the sectional area of the tube which are in the Kew marine barometer 1*25 inches and 0*25 inch in diameter respectively. The number of inches indicated at the top of the fixed scale is the number of inches marked off from a given point on the cistern, and each of the inches on the scale Fig. 57 below this are true inches less 0-04 inch. Kew Marine barometers are fitted with an arm made of hammered brass, which fits into a socket attached to a bulkhead, and as an additional security against jolting the arm is provided with a hinge at its upper side where it fits into the socket, and the barometer is slung in gimbals, so that in whatever direction the ship may move, whether rolling or pitching, the barometer hangs vertically, the arm being sufficiently long to prevent the instrument from touching the 217 bulkhead against which the arm is fastened. The vernier in the Kew Marine is similar to that in Fortin's barometer. All good barometers have a thermometer attached, so that the temperature of the instrument and the temperature of the mercury contained shall be known at the time of observation. The Syphon barometer, as we have already said, consists of a U tube, the long arm of which is closed and the short arm open. The tube is rilled with mercury so that there is no air above the mercury in the closed arm ; when placed in position, the mercury in the closed arm will, as in the ordinary straight tube instrument, fall to a certain level, depending upon the weight of the atmosphere at the time, and above it will be a torri- cellian vacuum ; a rise in the long tube causes a fall in the short tube, and vice-versa. The differ- ence in the two readings gives the actual height of the barometer, thus, suppose the long arm shows 36-5 inches and the short 6*4 inches, the reading = 30' I inches. Capacity correction depends on the ratio of the area of the tube to the area of the cistern, the larger relatively the cistern is to the tube, the less will be this error or correction. The necessity for a capacity correction is understood if we sup- pose the scale to be laid off from a certain point which is called the neutral point ; now if the barometer rises in the tube it must fall in the cistern, and the difference between the new level and the neutral point will have to be added ; con- Fig. 58. versely, if it falls in the tube it must rise in the cistern, and the difference must be subtracted. Capacity correction remedies this. Other errors are : Index error, which may be additive or subtractive, and is determined separately for each instru- ment, and Capilliarity, this varies with the tubes employed, and is less with boiled tubes than other tubes ; the capilliarity correction is always additive. There are also certain cor- rections required for all instruments, viz. : those for tem- perature and altitude. Aneroid Barometers are instruments for measuring atmos- pheric pressure without the aid of a fluid, hence the name aneroid a (privative) and v^po's (water). These instru- ments are, as a rule, very sensitive, and generally very 2l8 accurate, but owing to the deterioration of the mechanism from rust, or possibly from injury through rough usage, they may become incorrect. They are very convenient for travellers, and instruments are made which are so graduated, that the height above sea level, or the height to which the traveller has attained, may be determined by observing the atmospheric pressure indicated as an ascent is made. The construction of an aneroid barometer is as follows : two corrugated German silver discs are soldered together so as to form an air-tight box, which is then exhausted, or nearly exhausted of air, and fixed to a metal plate by means of a pin; if atmospheric pressure increases, the top and bottom of the box are approximated, if pressure diminishes, they tend to separate. By means of a spring which resists compression, and so supports the top of the vacuum chamber, pressure is measured and the movements which occur are communicated to a lever compensated for changes of temperature by being composed of iron and brass ; this lever is in turn connected to a chain wound j-ound a spindle which carries an index. As the box expands with diminished pressure, the chain moves the pointer to the left, and when the chamber is com- pressed it moves the lever to the right. The chain would tend to become slack when pressure diminished were it not for a watch spring which keeps it always w r ound round the spindle. The ordinary barographs in use are aneroids, the pointer of which carries a pen which gives a tracing on a chart carried by a clockwork revolving drum, and so we are able to have continuous readings of the barometer for a week at a time, after which the clock is again wound up and a new chart placed in position. At important meteorological stations, such as Kew Observatory, a photograph is taken continuously by means of a pencil of light falling on sensitised paper through the Torricellian vacuum of an ordinary mercurial barometer. Ordinary altitudes may be calculated according to the method devised by Mr. R. Strachan, which is as follows : Take the difference in barometric pressure between two places in one-hundredths of an inch and multiply this difference by nine, and the result will give the difference in height between the two stations in feet. For moderate heights and ordinary temperatures, starting at sea level, the barometer falls one inch for a rise of about 900 feet ; e.g., If the barometer at sea level shows 31 inches of pressure, at 857 feet elevation it will record a pressure of 30 inches ; at 886 feet 29 inches ; after 918 feet more 28 inches; and after an additional 951 feet it will stand at 27 inches. As we ascend, the air becomes rarer through a considerable portion of the atmosphere being 2I 9 below it, we have to ascend greater and greater distances for a corresponding fall of pressure. It will be seen that for a fall of four inches we have to ascend 3,612 feet, which gives a fall of one inch for every 903 feet as an average fall for readings at these heights ; but when we get up higher, the fall in the barometer for each succeeding 900 feet is well under the inch, so that the factor nine previously mentioned, must be in- creased. The following table shows the factor to be em- ployed, and the method of using the table, fig. 59, is as follows- Suppose you have two stations A and B, and it is required to ascertain the difference in height between them ; take the mean of the two barometric readings at A and B, and also the mean temperature at these two stations and see on the charts where one of the slanting lines cuts both of these values, and note the value of the slanting line as indicated ; this value is the factor which must be used to multiply the difference in the readings between the two stations in order to get the difference in height between them. 1 23 24 ^ 5 25 t c 26 ^ * 97 . 27 ^ 28 J* 29 30 Tl X "^ "x *s^ 5^ 4 ^^ ^ ^^^ II 23 24 25 26 27 25 29 30 SI X SIY^ ' * ^s X *% 12 ; >., ^s " X X * - * % X x V * ^ .. X ^ k% ^ ^x ^ ^X "x X x -. % ** *, ^ ^x M$ % i^ ^^s X X ""*. ' ^ X ^ ""- ". X ^ ^ a < ^ X \ X X , "X 30 40 50 60 70 50 90 MEAN TEMPERATURE Fig. 59. 220 For example : The barometric pressure at A is 30 inches, and at B it is 28 inches, the mean of these is 29 inches, and the temperature at A is 60 and at B is 40, the mean of which is 50 ; on referring to the chart the slanting line which cuts 29 inches and 50 is nine, so now taking the difference between A and B in T nu of an inch, we get a" o = 100, and this multiplied by nine, gives a result 900, which is the difference in height between A and B taken in feet. Supposing A has given a reading of 26 inches and B of 24 inches, and the mean temperature had been 40, we should have had io'5 as the factor as represented by the slanting line, and the height of B above A would have been 200 x 10*5 = 2100 feet. In distributing water, it frequently happens that the water has to be conveyed from a higher to a lower level by means of a syphon. In cases where it has first to be carried over some object above the level of the fluid at the higher level, the height to which the fluid can be taken in this manner is dependent on the atmospheric pressure, so that in constructing syphons, the lowest pressure which may be experienced at anytime has to be taken into consideration. Effects of decreased or increased atmospheric pressure : Diminished Pressure. The effects of diminished pres- sure begin to be noticeable when a height of between 2,800 and 3,000 feet has been attained, these consist in quickened respiration and pulse, increased evaporation from the skin and lungs (due to the dryness of the air), and diminished secretion or urine, the appetite is improved and there is a buoyancy of spirits with an increased capability for exercise. When the diminution in pressure equals between five and six inches of mercury, then congestion of mucous membranes oc- curs followed, if the air be very rarefied, by haemorrhages from these parts, there will also be dyspnoea, headache, and a feeling of weightiness about the limbs. Mountain air, where there is considerable diminution in atmospheric pressure will aggra- vate the following conditions: pulmonary emphysema, chronic bronchitis, and bronchiectasis, cardiac affections and diseases of the great vessels, tuberculous laryngitis. Diseases of the brain and spinal cord and neurotic conditions where there is a tendency to hyper-sensibility ; on the other hand many disorders and diseases may be cured or considerably benefited by mountain air with its rarefied atmosphere, such as chronic pleurisy, and cases where there is deficient expansion of the chest, early and chronic tuberculosis and haemoptysis due to tubercle where the disease is not too far advanced. Cases of anaemia improve wonderfully under mountain air because as in the case of tuberculous disease the dryness and stillness of 221 mountain air with the accompanying increase of diathermancy over that of the air at low levels permit the full effects of sun- shine and an open air life without the enervating effects of a high temperature. Increased Pressure, The circumstances under which atmospheric pressure sufficiently increased to give rise to symptoms are experienced, are during diving operations and work in caissons (pneumatic chambers), for the construction of piers and foundations of bridges at great depths where work is sometimes conducted under a pressure equal to that of two or three atmospheres ; the pressure of the air in deep mines is naturally greater than that at the surface, but the difference is so slight that it may be disregarded. Where the pressure amounts to that of two or three atmospheres, the following symptoms may be noticed prickings, headache, deafness, preceded by singing in the ears, epistaxis may also occur; the danger, however, is not so much in the increase of atmospheric pressure as in the too sudden removal of pressure, if divers are allowed to come to the surface too suddenly, haemorrhages into the spinal cord or elsewhere are liable to occur, followed by paralysis or death, and the same thing oc- curs in pneumatic chambers when workmen emerge from them without the precaution being taken of reducing the pressure gradually by means of air locks. 222 CHAPTER II. HEAT. The term climate is used to convey an impression as to the meteorological conditions existing in a country or place dependent upon temperature and relative humidity. Temperature is the quality of a body in virtue of which it feels hot or cold, and this feeling of heat or cold is materially affefted by the conductive power of the body. \Yhen heat passes from one body to another the one which loses heat is said to be the one of a higher temperature. Heat can be expressed quantitatively, and the unit of heat is the amount of heat required to raise i-lb. of water from o to iC. The specific heat of a substance is the ratio of the amount of heat required to raise a given mass of the substance iC to the amount of heat required to raise an equal mass of water from o to iC. The relation between heat and temperature has been compared to the difference between the quantity and the level of fluid in two vessels ; the level in two vessels of dissimilar size may be the same, and yet the quantities of fluid widely different, likewise the temperature of two substances may be the same, and yet the amount of heat contained in the two masses widely different. Heat is the effect of radiant energy on matter, more es- pecially of the comparatively long and slowly vibrating waves. The difference between a body in the solid, liquid, and faseous states depends upon the rate of motion of its particles, n solids the particles vibrate slowly and cohesion confines these vibrations to very minute paths. In fluids the particles show much more internal movement, and this movement has in part overcome cohesion and the body shows fluidity. In gases the vibrations are so large that cohesion has been over- come, the particles do not interfere with one another until they come very close together and then repulsion takes place between them. This molecular theory explains the pheno- menon of evaporation, with which we shall deal later on. Heat is the total amount of molecular vibration. Tem- perature depends on the rate of that vibration. The length of heat waves, like other waves, refers to the distance between the crests (C) or troughs (T) of the waves, amplitude to the depth from crest to trough vertically. In the figure the double-headed arrows A and L indicate amplitude and length. When the temperature of a body is raised, the Fig. 60. length and amplitude ot the vibrations of its particles increase, the result is that the body expands or becomes less dense. The co-efficient of linear expansion of a substance is the ratio of the increase in length of a bar of the substance, the result of an increase in its temperature of iC, to the original length of the bar at oC. Expansion of bodies by heat is taken advantage of in the construction of thermometers. Fluids are for ordinary pur- poses the most convenient, and of these alcohol and mercury are the only ones which we need consider here ; alcohol being employed for low and mercury for high temperature. Advantages of Mercury. Mercury can readily be obtained pure. It has a low specific heat, and is a good conductor, readily acquiring the temperature of the body in contact without chilling it to an appreciable extent. It is liquid through a wide range of temperature, viz. : from 40 F to + 662F. It does not wet the envelope in which it is contained. Alcohol has the advantage of remaining liquid at a tem- perature at which mercury is solid. Thilorier exposed alco- hol to a temperature of I48F without freezing it. It has the disadvantages of being less sensitive and of volatilising at even moderately high temperatures. In making a thermometer it is important that the tube should have been calibrated, and any tube with inequali- ties of bore rejected. The bore should be very slight -compared with the ex- ternal diameter of the tube, The bulb should be thin, and exposing a wide area. Before a thermometer is graduated it ought to be laid aside for some considerable time, in order to allow the glass to con- tract to its permanent size. This period may be considerably 224 reduced if the thermometer has been annealed by Denton's process with hot oil. Thermometers should be graduated by first plunging the bulb and a portion of the stem into melting ice and leaving it there for some little time, then the exa6t position of the column is noted. It is important to note that the melting point of ice and not the freezing point of water is taken as the starting point, because many circumstances affect the freezing point of water, whereas the melting point of ice is constant. The boiling point is determined by immersing the instrument in steam, generated by an instrument called a hypsometer, and it is important in making this point to note the height of the barometer, as the barometer affe6ls this temperature considerably, and the boiling point should mean the temperature at which pure distilled water boils, when the barometer stands at 760 millimeters or 29*92 15" of mercury at oC at the sea level in latitude 45, every alteration of pressure affects the boiling point in the proportion of i'4F for every difference of \" mercury in barometric pressure. The boiling point at elevated stations is so low that it is insufficient to conduct the ordinary purposes of cooking, the temperature, therefore, has to be increased either by boiling the water in some apparatus like Papin's digester, or by adding saline substances to raise the temperature of the boiling point. To show the effect of pressure, water boils at a pressure of 20'355 ins. mercury, or 10 Ibs. per sq. in. at temp, of IQ3'3F. 29*922 ins. ,, 14-706 Ibs. ,, ,, ,, 2i2 - oF. 40710 ins. ,, 2O'Ooo Ibs. ,, ,, ,, 228"oF. 81-420 ins. ,. 40*000 Ibs. ,, ,, ,, ' 267'3F. 610-653 ins. .. 300-000 Ibs. ,, 4 I 7'5F. The temperatures attained by high-pressure steam ex- plain the disastrous results seen in boiler explosions amongst those whose misfortune it has been to be exposed to ir. The graduation of a thermometer should be made on the stern. This is done by coating the stem with a thin layer of beeswax, and with a fine sharp steel point making the neces- ary markings, divisions, and numbers through the wax down to the glass, so that the glass is exposed at the places where the markings are required. The thermometer is then exposed for about ten minutes to the vapour of hydrofluoric acid, which marks the glass. The wax is removed when the etching is complete, with turpentine. The thermometers required for the ordinary meteoro- logical observations consist of a maximum, minimum, dry bulb and wet bulb thermometer, and also blackened bulb in vacuo 22 5 thermometer for solar radiation, a minimum thermometer for terrestial radiation, as measured about 2 or 3 inches from the ground. Thermometers for taking the temperature of the subsoil air and water at depths of 2, 3, and 4 feet, and lastly a standard thermometer with Kew certificate for testing the other instruments with occasionally. The maximum, minimum, dry and wet bulb thermometers should be of the best description, have the scale divided on the stem, and be furnished with a certificate as to the corrections required with each instrument at the various temperatures. The scales of the thermometer are in degrees Fahrenheit. These four thermometers are exposed in a screen. On board ship a wall screen, consisting of a box with louvred sides is used, and on shore the one usually employed is that known as Stevenson's screen, which has double-louvred sides and front, a double roof, the upper one being about an inch above the under one, which is pierced with holes ; the roof should incline from front to back and overlap the body of the screen by about 2 inches. The front of the screen opens downwards (by means of hinges placed at the bottom) away from the sun, i.e., towards the north in the Northern Hemi- sphere, and towards the south in the Southern Hemisphere. The bottom of the screen consists of three boards so arranged that the centre one is about half-an-inch above the other two. Its construction thus allows a free circulation of air on all sides, and at the same time prevents rain or the direct rays of the sun from striking the instruments, which are fixed on up- rights near the middle of the screen. The. dimensions of the screen are : length, 22 ins. ; breadth, 14 ins. ; height, 18 ins. It is supported on legs so as to be 4 feet above the ground, and should be painted white. The relation of the three scales is a? follows Between the melting point of ice, which is 32 degrees on the Fahrenheit scale, and the boiling point of water, there are 1 80 degrees. Between the same temperatures, Centigrade and Reaumur there are respectively 100 degrees and 80 degrees. The three scales .'. bear to one another the following ratios F 32 : C : R :: 180 : 100 : 80 F- 3 2 : C : R :: 9 : 5 : 4 To convert Centigrade into Fahrenheit, multiply by 9, divide by 5, and add 32 ; or a quicker way is to multiply by 2, subtract one-tenth of the product and add 32. With thermometers marked so as to show degrees Centi- grade and Reaumur, if we wish to express any particular 226 temperature taken in either of these scales, in degrees Fahren- heit, this may be done by adding together the values in degrees C and R and adding 32 to the sum. The Maximum thermometer employed is usually one in which the index is a portion of the column of mercury detached by a minute bubble of air (Phillip's) or one in which there is a constriction between the bulb and the stem (Negretti's) in which case, when the mercury expands it is forced past the constriction, and when it contracts it is left behind, because the cohesive power of mercury is insufficient to withdraw the thread when contraction occurs as a result of diminished temperature. The Minimum thermometer usually met with is the spirit one of Rutherford, which depends for its action upon the fact that spirit wets the glass, and the surface of the spirit is there- fore concave ; the free surface behaves in a different manner to the rest of the liquid by reason of its surface tension, so that if a small index of glass be contained in the fluid, it is drawn back by the surface of the fluid when the fluid contracts, but remains stationary when the fluid expands, the index will not break through the surface of the fluid, unless force be used. The instrument is set by inclining the thermometer gently so that the index is left at the surface of the spirit. Fig, 61. CASELLA'S MERCURIAL MINIMUM THERMOMETER, It would be well to mention a mercurial minimum ther- mometer devised by the late Mr. Casella, as a substitute for the instrument just described, which is intended for use more especially in hot climates where error is liable to occur from evaporation of the spirit. It consists of a mercurial thermometer, with a bulb and stem of the usual pattern, but a short distance from the bulb and in connection with the main tube is a small tube of wider bore, opening out and bending backwards, this terminates in a little pear-shaped chamber the entrance to which is larger than the bore of the main tube. The action depends in part on the adhesive property of mercury to glass in vacua , and also on the fact that when two tubes are united to one bulb, the fluid will recede by contraction in the smaller, and rise by expansion in the larger. The instrument is set by inclining the bulb so that the mercury flows into the main tube and bent part of tube, but leaves the chamber empty. The instrument should after being set indicate the temperature at that time, but should the temperature rise or fall after setting, the lowest temperature which has occurred will be the temperature indicated. The thermometers employed for measuring the intensity 'of solar and terrestrial-radiation have been already mentioned the one employed for solar radiation consists of a mercurial maximum thermometer having the bulb and a portion of the stem adjoining the bulb coated with lamp black, the thermo- meter is enclosed in a glass tube having a bulb 2\ ins. dia- meter blown in such a way that the thermometer can be enclosed without touching the outer tube by means of little clips placed on the stem of the thermometer ; before this outer case is sealed the air is exhausted and we then have a blackened bulb thermometer in vacuo. The reason for blackening the bulb is that by so doing you offer a surface to the rays of the sun which is a good absorber, and so prevent the loss which would occur from the reflection of heat rays from the glass forming the bulb of the thermometer, by en- closing it in the glass case the lamp black is prevented from washing off, the thermometer is also protected by it from the cooling influence of the wind. This by some is regarded as a disadvantage, but an action which we fail to regard in that manner since the black bulb thermometer is merely an instru- ment for estimating the intensity of solar radiation and not for taking the temperature of the air. We mentioned the fact that the glass case for this thermometer is exhausted of air, this is done so as to avoid the loss of heat which would occur if the instrument were surrounded by a medium not perfectly diathermanous, as air containing aqueous vapour would be. The black bulb thermometer is placed on a stand 4 ft. from the ground in a perfectly exposed position, such as all meteorological observatories should possess, with the bulb of the instrument pointing to the S. or S.E. if in the Northern hemisphere, and N. or N.E. in the Southern hemisphere, so that it may at all times be exposed to the sun. The terrestrial radiation thermometer is merely a spirit minimum thermometer, usually for protection, enclosed except the bulbar portion, in a glass tube having at the open end a perforated cork through which the bulb projects. It is sup- 228 ported on two forked twigs so as to be about 4 inches above the ground, which where this thermometer is exposed should Fig. 62 TERRESTIAL RADIATION THERMOMETER. be covered with short grass. When the ground is covered with snow the instrument should rest on the surface of the snow. These together with all the other meteorological instru- ments should be set after the readings have been made at the 8 a.m. observation of instruments. In choosing a health resort it is important to know the amount of solar radiation which the places under considera- tion receive. We have described the black-bulb thermometer in vacuo for measuring the intensity of solar radiation ; it remains to describe the method of recording its duration, that is to say, to determine the daily number of hours of bright sunshine which any particular place enjoys. The instrument usually employed is one in which the sun's rays, whenever they appear, are brought to a focus upon some material which will be charred, such as a piece of cardboard for the daily records, or a piece of wood for half-yearly records. The Campbell-Stokes Sunshine Recorder is the one usually employed, but there is a modification of this instrument possessing certain advantages over it, known as the Whipple- Casella Sunshine Recorder, which is more costly. In both instruments a record is obtained by the charring of the card- board through the sun's rays being brought to a focus by means of a sphere of glass. The Campbell-Stokes recorder consists of a glass sphere four inches in diameter which stands on a small iron pedestal slightly cupped at the top ; the glass bulb is partially surrounded by an iron frame which is moveable, which, when the instrument is placed is position, is set at an angle to the horizon corresponding with the lati- tude of the place, and when so set for a given place is not altered. The centre of this frame must be placed so as to face the sun at noon, i.e., due South if used in the Northern hemis- phere, or due North if employed in the Southern hemisphere. The frame contains three sets of grooves in one of which fits 229 a card of size and shape suitable to the season ; each card is marked out into divisions corresponding with the hours, half- hours, and quarters, so that the sunshine recorder is not only useful for establishing a record of when and for how long during the day the sun was shining, but it also serves as a sun-dial. The cards employed are of three sizes and shapes, short curved cards fitting in the upper grooves being employed in winter, broader and rectangular ones for insertion in the middle grooves at the equinoxes, and longer and more curved cards are placed in the lowest set of grooves during the summer. When placing a sunshine recorder in position, care Fig. 63 THE WHIPPLE-CASELLA UNIVERSAL SUNSHINE RECORDER. must be taken to see that the base of the instrument and the axis of the frame carrying the card are perfectly horizontal, and it must not be forgotten that, like a sun-dial, it requires to be placed in a perfectly exposed position, so that at no 2 3 time of the day objects, such as trees or buildings, come between it and the sun. If the records are taken for the ordinary civil day, a fresh card must be placed in the frame every evening after sunset / but if the records are only re- quired for the previous 24 hours, then the cards can be changed when taking the meteorological observations of a morning. The construction of the Whipple-Casella sunshine recorder is well shown in the accompanying illustration ; it requires adjusting for latitude when first set up and then altered from time to time to correspond with the varying meridian altitude of the sun, which thus enables cards of uniform pattern to be employed all the year round. The record consists of a burnt track on the cardboard slip, obtained by means of a sphere of glass which acts as a burning glass, always in focus, as in the description of the other instrument. The value of bright sunshine when unaccompanied by too intense heat, as a restorative to those debilitated from any cause, can scarcely be overestimated ; therefore, at all stations where meteorological records are kept, the duration of bright sunshine, from day to day, should always be noted. Effects of Heat and Cold. Heat. Residence in the tropics for a long period is attended with certain disadvantages. Although there are many brilliant exceptions, a prolonged resi- dence in the tropics tends to lower the vitality and incapacitate the subjects for prolonged mental effort, and is apt to make peo- ple become listless and apathetic. Much of the mental lethargy in these cases is no doubt due to excesses and over-indulgence, notably in eating and drinking, but it cannot all be explained in this way. When a person from a temperate climate mi- grates into the tropics, metabolism is diminished and less food is required in consequence. Respiration is slowed and the diminution in rate is not entirely compensated for by an in- crease in depth, consequently less carbonic acid is evolved and less oxygen is absorbed. Dr. E. A. Parkes pointed out the difference between the amount of CO 2 exhaled by a similar individual in a temperate climate and in the tropics by ex- pressing it in terms of carbon ; if in a temperate climate 10 ozs. of carbon were expired, only 8*157 ozs - wou ^ be expired in the tropics. High temperature such as is met with in warm climates slows the heart about 2\ beats per minute. The skin acts more freely, so that as long as evaporation from the surface in the form of perspiration is unchecked, no great discomfort will occur, but once this is interfered with, as would be the case when the air is saturated with moisture, then the 231 effects of exposure to a high temperature are soon felt. The excess of work thrown upon the skin in those as yet un- accustomed to a high air temperature gives rise to a hyper- aemic condition of the skin and prominence of the papillae, resulting in the formation of vesicles which occasionally be- come pustules. The places which are most trying to Europeans are those with a mean annual temperature of 80 or thereabouts, with a small range, that is to say, where the temperature varies little above or below the mean temperature ; these places are, for the reason already stated, especially trying if, as is almost in- variably thecase, the air is nearly saturated with aqueous vapour. Cold, A moderate degree of cold stimulates the circula- tory and respiratory movements, appetite increases, and the brain is capable of performing its higher functions with greater ease. Excessive cold acts by contracting the arterioles to such an extent that the circulation is so much interfered with that stasis occurs, and if the cold be continued, too long, gangrene of the parts exposed (frost bite) occurs. A remark- able feeling of languor precedes a condition of coma, which in turn is followed by delirium, with a delusive sensation of heat. People who have been exposed to the extreme cold of blizzards and died from its effects have generally been found more or less undressed, the sensation of heat due to the disturbance of the cerebral circulation leading them to divest themselves of their clothes. Extremes of cold in a still atmosphere have been experienced without any ill effects. In accounts of arctic exploration we read of people being exposed to a temperature of 50 or 60 without feeling the need of any unusual amount of clothing; simply because on those oc- casions the air was still, and from the low temperature neces- sarily dry. 2 3 2 CHAPTER III. AQUEOUS VAPOUR. The proof that the amount ot vapour which a space is capable of containing is dependent solely on the tempera- ture is shown by the following simple experiment : Take three clean dry tubes, each three feet long and closed at one end ; fill them with mercury, taking care that no air enters, invert them over a pneumatic trough filled with mercury, and note that the heights are equal in ~11 three. Call one A, another B, and the third C. Ler e A as a standard. Into B introduce a few drops of water, so that after a few minutes there is still some water which has not evaporated. Into C pass a little dry air so the mercury is de- pressed say, two inches, mark the tube at this point and then insert a few drops of water into tube C, so that there is still a little water on the surface of the mercury ; note the height of this barometer. The temperature was, for example, 59 F ; after the introduction of water into B the barometer fell say, o - 5 inches ; but in C, which contained air, there was an appreciable fall, but not equal to o'5 inches. Now, depress tube B ; it will be found that the level of the mercury in B will always be o - 5 inches below the level of the mercury in the standard tube until all the aqueous vapour is condensed into water, and nothing but mercury and liquid water occupy the tube. Lastly, depress tube C until the mercury stands at the same level it did before the introduction of the water ; it will be seen that in order to cause the mercury in the tube to stand at the same height, or in other words, for the air to occupy the same space, C will have to be depressed 0*5 inches, which proves that aqueous vapour can exert the same amount of pressure in the presence of another gas or gases having no chemical affinity for it as it does in a vacuum. If we increase the temperature of the chamber in which the tubes are, the more it is raised the more will the mercury be depressed. It is understood, of course, that in every case sufficient water is always present to prevent it all being evaporated at the temperature at which the experiments are conducted, then it will be seen that for every tem- perature the barometer is depressed a certain amount which 233 is invariable, and the higher the temperature the greater is the amount of depression of the mercury, or in other words, the greater is the amount of aqueous vapour present. From this it is seen that the pressure which a vapour can exert in the presence of its liquid is dependent solely on the temperature, and the presence of another gas or mixture of gases having no chemical affinity for it does not afTect this pressure in any way, or expressed differently, gases and vapours act toward one another as vacua. A similar experiment with ether can be easily performed to illustrate the same law, and also show that at the same temperature the vapours of different substances exert different pressures. The pressure which aqueous vapour is capable of exerting at any temperature in the presence of water is there- fore known as its vapour tension. The hygrometric state of the air is expressed either as relative or absolute humidity ; by relative humidity is meant the percentage of saturation existing, taking saturation as 100. Absolute humidity refers to the actual amount of aqueous vapour present in the air. Relative humidity is frequently highest when the absolute humidity is very low ; thus, in winter the relative humidity may be nearly at the point of saturation, whereas the actual amount is small; whilst in summer we frequently have the air containing considerable amounts of aqueous vapour with a relative humidity far short of saturation. Saturation may be defined as the condition of the at- mosphere when it is no longer capable of containing any more (aqueous) vapour without an increase of the temperature. The temperature at which the point of saturation in a given space is reached is called the dew point. Hygrometers are instruments for measuring the amount of aqueous vapour in the atmosphere, they may be either direct or indirect. Direct hygrometers show the dew point at once by means of a thermometer. Indirect hygrometers require observations to be made in conjunction with certain cal- culations. The commonest direct hygrometers are Dine's, Daniell's, and Regnault's. Dine's consists of a metal box covered with a piece of polished glass, in con t aft with a sensitive ther- mometer, and so constructed that a flow of water through the instrument can be made to take place at will. The tempera- ture at which dew is deposited on the outside of the glass after water has been flowing through the box is the temperature of 234 the dew-point. Observations are checked by noting the temperature at which the dew begins to disappear, after the flow of water through the box has been stopped. In Daniell's hygrometer we have two bulbs connected by a bent tube : one is made of blackened glass, and contains ether and a thermometer, the scale of which is visible above the blackened glass bulb ; the other bulb is made of clear glass, and is wrapped round with a little clean muslin. To use the instrument, ether is poured on the muslin bag and allowed to evaporate. Evaporation from the muslin cover, causes the temperature of the. bulb to fall, any ether vapour contained within is condensed ; this condensation converts the apparatus into a retort and condenser, and the process of distillation lowers the temperature of the black bulb contain- ing liquid ether by enabling evaporation to occur, so at length it is chilled to such an extent that the dew-point is reached, this is shown by the bulb becoming bedewed with moisture condensed on the outside. The temperature must be noted as soon as evaporation ceases from the muslin-covered bulb, for this bulb then ceases to act as a condenser, and as a result evaporation ceases to take place from the ether in the black bulb, the temperature of which now commences to rise, and the dew r on its outside at length disappears. The temperature at which it begins to disappear should agree with the temper- ature at which it began to be deposited. The mean of the two readings is taken as the dew-point. In Regnault's hygrometer the same result is brought about in a different way. It consists of a silver or silvered glass vessel, closed at its top except for an inlet and outlet tube w T hich is capable of being connected with an aspirator, it also contains a thermometer and some ether. To work this hygrometer, air is drawn through the instrument, the ether evaporates and the vessel is chilled, dew is deposited at length on its outside, and the temperature at which this occurs is noted as in Daniell's hygrometer. Of the indirect hygrometers, the wet and dry bulb ther- mometers of Mason is the best known, its use is restricted to warm and temperate climates ; as it is unsuitable for extreme climates, such as those of Russia and Canada. The wet and dry bulb thermometers consist of two thermometers as nearly alike as possible, the one employed as a wet bulb one, is coated with muslin, and attached to this is a small strand of wick or worsted free from grease which dips in a small vessel kept filled with pure distilled water. The dry bulb thermometer is exposed uncovered in close proximity to the wet bulb instrument. The less saturated 235 the air the quicker will the water evaporate, and there- fore the greater will be the difference between the read- ings obtained by the two instruments; when the air is saturated evaporation ceases, and the instruments show the same temperature. Formulae, based on the fact that this evaporation continues until saturation is reached, have been devised for determining the dew point, and tables constructed. It is necessary to understand the nature of this process of evaporation, the theory of which is explained on page 239. By evaporation is meant that process by which liquids and solids assume the gaseous state at their free surfaces. The term " vapour " is generally understood to mean a substance in a gaseous condition, which can exist as a liquid or a solid at ordinary pressure and temperature. Fig. 64. WET AND DRY BULB THERMOMETER. Tables constructed by Glaisher can be obtained, which show at once the temperature of the dew point, the relative humidity, and the amount of moisture contained in a cubic foot of air when certain temperatures are shown by the dry and wet bulb thermometers, or, if we have Glaisher's Factors and Glais- her's Tables of Vapour Tension at various temperatures, we can determine the dew point and relative humidity. In this case we first observe the factor corresponding with the dry bulb temperature, call this F. Then take the difference between dry and wet bulb readings, call this D. Now multiply F by D and subtract the result from the dry bulb temperature, and the result is the temperature of the dew point, thus, dry bulb temperature F D = temperature of dew point. Having found the dew point, we next refer to the Table of Vapour Tensions given for various temperatures. Note what the vapour tension corresponding to the dew point is, call this D.P. tension. Next look for the vapour tension cor- responding with the dry bulb temperature, call this dry B. tension. Then to find relative humidity we say, dry B. Tension : D.P. Tension : : 100 : X, or D.P. Tension x 100 _ Relative Dry B. Tension " Humidity. If either the dew point temperature or dry bulb tem- perature be intermediate between two readings given in the tables, calculate as in the following example. Say dew point temperature was found to be 59*5 then Vap. tension at 60 -518" 59 = -500" Difference for an increase of i o'oiS" .'. for o'5 it 0*018 X -5 = -009." So vap. tension at 59-5 = 0*500 + 0.009 '509'' ; or again, say dry bulb temperature was 60-7, then vapour tension at 61 =. '537," and at 60 = '518 .'. difference for an increase of i at 60 = 0-019," and for 0-7 = 0-019 x o'y = '0133, and vapour tension at 607 will be 0-518 + 0-0133 which = 0-5313. The vapour tension at the dew point may be found from the dry and wet bulb readings, provided you have a table of vapour tensions (as in Appendix q.v.), by the use of Apjohn's formula, which is as follows : F' tension corresponding to wet-bulb temperature. F" = tension of vapour at the dew point. D = dry bulb temperature. W = wet bulb temperature. 87 = a constant for temperatures when dealing with temperatures above 32 F. 96 = a constant for cases when the temperature is below 32 F. 237 D - W Then for temperatures over 32 F, F" = F' 8? To take an example : Dry bulb temperature = 44 F. and wet bulb temperature = 43. On referring to tables -we see that the tension corres- ponding to 43 = 0-277". F" = 0-277" - *V, so F" = 0-277" -- -01149" and F" = 0-26551". The formula here employed is Apjohn's in its simplest form, if greater accuracy be desired then we must allow for pressure, and this is done by multiplying the result by the pressure as found, and dividing by the standard pressure. Under ordinary circumstances the difference is so slight as to render the correction unnecessary. In questions affecting ventilation it is always to be borne in mind that varying amounts of aqueous vapour in different portions of the atmosphere (for example, as within a room and in the outside air) affect its density considerably. It will readily be understood how this occurs if we con- sider that the air' is a mechanical mixture, composed (practi- cally) of 4 molecules of nitrogen and i molecule of oxygen and occupying the space of 5 molecules with a molecular weight of 144; now molecules of water vapour occupying the same space will weigh 90, .'. air is heavier than water vapour in the proportion of 8 : 5. It often becomes necessary to calculate the weight of a given volume of air containing a certain amount of moisture so as to compare it with another equal volume of air containing either more or less aqueous vapour. Suppose then we require to know what would be the weight of a cubic foot of air with a temperature of, say, 60 F. and with the dew point temperature 56 and barometric pressure 29-5 inches ? We know that a cubic toot of dry air at 32 F. and 30 inches pressure weighs 566-9 grains, and that the volume varies inversely with the pressure and increases T? for every increase in temperature of 1 C., or ^T for every 1 F. .'. to find density A B 459 + 32 A = - x x 566-9 grains 30 459 + 60 This would be the weight of the air if there had been no moisture present, but the dew point was 56 F., and vapour UB* OF THE UNIVERSITY 238 tension at 56 = -449 inch, so that the pressure at the time of observation = B f of vapour tension. '.' Dry air is to aqueous vapour as 8 : 5, so the pressure will be dimished by f of the pressure exerted by the aqueous vapour present, so to find the weight of a cubic foot of moist air at B pressure when dew point = 56 F., and vapour tension* .'. = '449 inch, we have B - f x "449 459 + 32 A 566*2 X X 30 459 4- 60 = 523-8 grains. A cubic foot of moist air .". weighs less than a cubic foot of dry air at the same temperature by reason of the loss of density due to the barometric pressure being reduced by the loss of f of the existing vapour tension. Saussure's hygrometer is an instrument for indicating the relative humidity of the air by means of an indicator which points to a figure on a scale showing the percentage of saturation, it depends for its action upon the fact that a hair deprived of all grease, elongates and contracts according as the air is moist or dry. The mechanism of the instrument is as follows : A hair free from grease is made fast at one end, whilst the other passes over a pulley, with which is connected a lever acting as the index; the end passing over the pulley is fastened either to a slight spring or supports a weight. When the instrument is first made, it is so arranged, that with a saturated atmosphere the pointer stands at 100, and with an absolutely dry atmosphere at o. Humidity has perhaps more to do with the healthiness of a climate than anything else. A temperature, which in a dry climate is not at all ill-borne, becomes unbearable when the relative humidity is high. Air which contains little or no aqueous yapour is practically aseptic. Desert air owes it aseptic property to the absence of aqueous vapour. Mountain air which is so invigorating contains very little moisture. Certain affections, such as bronchitis and influenza, are relieved by a moist atmosphere, but catarrhal conditions and haemorrhagic phthisis suffer considerably from too much moisture in the air. Dr. Williams (Treatise on Hygiene) mentions the case of a. patient of his who was suffering from advanced phthisis and was staying in the South African Kala Hari Desert, the air of which was so dry that the difference between the dry and wet bulb thermometers amounted to 25 F., on one occasion a heavy shower of rain with a saturated atmosphere came on suddenly, and gave rise to a severe attack of haemoptysis on the part of the invalid. 239 Chemical hygroscopes are capable of great accuracy, for example, if a known weight of dry calcium chloride (Ca C\z) be contained in a tube, and a known weight or volume of air be made to pass over it, the increase of weight in the tube will show the amount of aqueous vapour present. In practice such a method is seldom, if ever, resorted to. The molecular theory has already been alluded to in a previous chapter to explain the gaseous, liquid and solid states, for by it we assume that liquid water consists of a number of particles vibrating with different veloci- ties in all directions, and so acting on one another as to constantly interfere with each others movements. Vapour in like manner is supposed to consist of particles moving with various velocities but not interfering with one another until they come very close together. The velocities of both sets of particles increase as the temperature rises. In this theory it is also assumed that there is a force on either side of the boundary between liquid and gas, which tends to prevent the escape of particles from the liquid. If a particle within the liquid is moving with sufficient force it will be able to burst through the boundary and will then be free and become a particle of gas. The higher the temperature, the greater will be the velocity of the particles and the greater will be the number making good their escape. At the same time some of the particles outside will be moving in the direc- tion of the liquid, and be forced through and become liquid, the rate of evaporation therefore will depend upon the extent of the surface exposed and also on the number of particles of the gas above the liquid. And it can be proved by experiment, as already described, that the extent to which this process can proceed depends solely on the temperature, or in other words, that gases and vapours of different natures act towards one another as vacua (Dalton's law). When the air or space is saturated at any temperature it merely means that condensa- tion and evaporation are equal, and that the loss is counter- poised by the gain. The rate of evaporation depends on the relative humidity of the air, conditions therefore which increase the capacity of the air for aqueous vapour, increase the rate of evaporation ; these are movement of the atmosphere, a high and increasing temperature, and absence of large quantities of water. How these act is too obvious for us to point out. The rate of evaporation affects health very considerably ; by means of evaporation we are enabled to withstand the effecls of high temperatures, a moderately high temperature and a low rate of evaporation being extremely depressing, whereas tempera- tures much higher and a dry state of the atmosphere can be borne without ill-effects. 240 When water evaporates a large amount of heat is used up in effecting a change of state from the liquid to the gaseous state, the heat being stored up or rendered latent, ready to be again given out when condensation takes place, one grain of water in evaporating uses up or renders latent as much heat as would raise 960 grains of water through i F. Since evaporation uses up or renders latent a large amount of heat, it follows that places near the sea, or wherever there is much water, are much cooler in summer than places in corresponding latitudes where there is no large water surface in the vicinity. When the air becomes colder the heat rendered latent by evaporation is again set free on condensa- tion, and the air is in consequence warmed ; so large expanses of water tend to prevent excesses in either direction. The amount of evaporation which takes pi ace. yearly at a place is a matter of considerable importance in determining the amount of water* which will be yielded by a given area after allowing for loss by evaporation. By Pole's formula we can determine the probable daily yield of the collecting area. E = annual loss of water by evaporation expressed in inches. Rm = average rainfall of a long series of years. 5 Rm = estimated average of the 3 direct consecutive years. A = area in acres of collecting ground. Then 62 Ax( * Rm E) = yield of water per one day, and this multiplied by n gives the amount for n days. The constant 62 is derived as follows: i acre yields with i inch of rain 22,635 gallons of water, and since the amount indicated by Rm refers to inches of rain- fall per annum, the value 22,635 m ust be divided by 365 if we require a constant which will show amounts per diem, so 22635 365 For example, it is required to know the amount of water which will result from the storage of ten days' rainfall when the mean annual rainfall is, let us say, 25 inches, in which case | of 25. which equals 20, will be the estimated average of the three direl consecutive years ; the estimated loss from evaporation is equal to 10 inches of rainfall, and the area of the collecting ground is 100 acres ; then the answer in this case will be: 62x100 [ (| xV-) 10] =62000, i.e., the number of gallons which will result from the storage of one day's rainfall, and therefore, for ten days it will be 620,000 gallons.* As a rule the evaporation in the higher latitudes is less than the rainfall, the balance between evaporation and rainfall * A gallon of water occupies 277-274 cubic inches, or i cubic foot will hold 6-232 gallons. 241 being restored by the excess of evaporation over rainfall which occurs over the sea in low latitudes. There are numerous instruments devised for determining the amount and rate of evaporation, many of them working upon different plans. For example, Wild, of St. Petersburg, weighs a given mass of water by a self-registering weighing apparatus, a record being obtained automatically every 10 minutes, which shows rainfall, rate of evaporation, and weight of snowfall. Richards has an apparatus which consists of a pair of scales, one of which supports a basin of water, the instrument is counterpoised when set, and any alteration occurring after- wards is recorded by a pen on a revolving drum. The Piche evaponmeter consists of a graduated tube, closed at one end and filled with water, the other end is covered by porous paper, when required for use it is turned so that the paper end is lowermost, water is evaporated from the paper and the paper receives a fresh supply constantly from the water contained in the tube. The alteration in the level of the water in the tube shows the amount of evaporation which has occurred. Lament's Atmidometer or Atmometer is another evapori- meter, which consists of a pan exposing a known area, this is connected with a cylinder to which is attached an indicator which can be moved up and down a graduated scale. The scale is set with the pointer at zero and water is poured in until it is flush with the surface of the pan, the instrument is left for a given time, after which, the water has fallen below the level it originally stood at, to a greater or less extent, according to the rate of evaporation. To obtain a reading, the screw working the cylinder is turned until the water is brought up once more flush with the level of the pan and the pointer will now be found to have traversed .a certain distance on the scale, andthis indicates the amountof evaporation which has occurred. Aqueous vapour influences solar and terrestrial radiation very considerably, but hardly to the extent to svhich at one time it was credited, since it is now known that dust and also water, in a minute state of subdivision, perform a very important share of the work in checking radiation. Things are often insufficiently appreciated until they are lost, thus it is when aqueous vapour is present only to a slight extent, that we are able to form an opinion of its action, for it is then we suffer from the effects of solar radiation by day, and terrestrial radiation by night; the protecting veil is then removed and we have an extreme range of tempera- ture. Good examples of this action are afforded by the air in the Sahara Desert and in the Arctic regions, both of which 242 are characterised by a remarkable absence of aqueous vapour ; in the former case the heat by day is intense because there is no protecting veil to keep off the heat rays, and at night the cold is intense because there is no protecting covering to prevent heat radiating off into space. Likewise in the Arctic Regions, the heat in the sun may be sufficiently powerful to melt the pitch in the seams of the deck, whilst out of the sun the cold is many degrees below freezing point. Aqueous vapour present in the air, as explained further on, acts by absorbing certain rays from the sun, producing in a spectrum black lines or bands in the yellow ; it is found that the breadth of this set of dark lines, known as the rain- band, is proportional to the amount of aqueous vapour con- tained in the air, and this band can be observed by means of a a spectroscope as illustrated (fig- 65). Aqueous vapour is also capable of retaining or absorbing a considerable amount of the heat waves from the sun, these waves can readily pass into an atmosphere containing aqueous vapour, but less readily pass out, so that the heat is as it were entrapped, just as it is by the glass of a green-house, which lets it pass in but interferes with its passage out. Fig. 65 RAIN-BAND POCKET SPECTROSCOPE. In regard to this absorption of certain rays from sunlight, certain vibrations or sound waves of certain length produce certain definite sounds or musical notes, different wave-lengths of light in what is termed the ether produce different colours. The .vapour of any substance when set in motion, vibrates at a certain rate and has wave-lengths of a certain definite length, which can be set in motion by vibration of waves of the same amplitude. Now, radiant energy in the form of light is made up of rays of very varying wave-lengths, and in passing through the vapour of any substance, or substance in the gaseous state, this vapour will be set vibrating by those constituent rays whose wave-lengths coincide with its own, and conse- quently those rays passing in and possessing the same wave- lengths, and only those will be absorbed. This can be" expressed tersely by saying a body absorbs the same kind of 243 rays as it gives out. A beam of white light possesses rays, some of which vibrate in unison with those of aqueous vapour when set in motion ; if therefore they pass through air contain- ing a greater or smaller amount of aqueous vapour, a greater or smaller amount of these waves will be absorbed, hence the absorption of those waves whose wave-length correspond with that of aqueous vapour and the formation of the band known as the rain-band. In the Solar Spectrum, as we have already said, the different colours are produced by rays of different wave- lengths, and the spectrum sorts out the rays according to their wave-lengths, thus the shortest visible light waves are the violet ones with a length of ^won of an inch, and the longest ones are the red with a length of *A i foot in 1000 feet, whereas in meteorology the vertical unit refers to the height of the barometer, and the horizontal unit is in geographical miles. The English and the Continental barometrical gradients are practically identical, thus : The English vertical unit is o'oi inch pressure, and the horizontal unit = a quarter of a degree or 15 geographical miles which = 17 statute miles. The Continental vertical unit is i millimeter = 0-03937 inches (which is practically 4 times *oi inch), and the horizontal unit i, w r hich = 60 geographical miles, which is 4 times the English horizonal unit. Now to give an example, if the barometer at a certain time stands at 3O'O5" at London Bridge and 30-000" at Ports- mouth, which is 85 statute miles distant from London Bridge, 257 then the difference for 85 statute miles which = 75 geographical miles = '05", and for 15 geographical miles it rz 'ox". So that between London and Portsmouth we should say that there is a gradient of i for S.E. winds, the isobars running from N.W.to S.E. Had the difference in pressure been 0*025" it would then have been 0-005" for 15 geographical miles, and the gradient would have been described as a gradient of 0-5. If it is required to find the gradient existing between any two places. The difference in height of the barometric pressure at the two stations multiplied by 15 and divided by the distance in geographical miles gives the difference per horizontal unit, and this is then expressed in integers or fractions of the vertical unit "Oi" of pressure. Thus in the case quoted '05 X J 5 = -01" which = a gradient of i. 75 The reason why the wind flows in from the S.E. instead of directly in from the N.E. as one would expect, is this : Air flows in from a denser to a less dense portion of the atmosphere, and the rotation of the earth accounts for the flowing in of the air in a direction which is inclined to the direction of the isobars instead of at right angles to them. Since the earth is constantly rotating on its axis from west to east, it follows that a body moving in a straight line in the northern hemisphere appears to be deflected to the right, and in the southern hemisphere to the left, this is accounted for by the fact that as a body approaches the equator it is con- stantly reaching a part of the earth moving faster than the place from whence it came, therefore in the case of a body moving directly towards the equator any lateral movement it received from the rotation of the earth at the place further from the equator would be insufficient to cause it to remain on the same meridian, and therefore it lags behind ; conversely a body moving from the equator to either pole is constantly reaching a place where the velocity of the earth is less than it was at the place the body has left, hence the apparent deflection to the right or the left according to whether it is travelling in the Northern or Southern hemisphere. Since the earth rotates on its axis once in 24 hours and the earth at the equator has a circumference of 24,900 miles, it follows that the speed at which any point on the equator rotates is 24,900 -f- 24 miles per hour, which = 1037*5 miles per hour, whereas in latitude 60 'a body has only about half the distance to travel and at the poles it would be o. The result of this rotation of the earth is that air flowing into an area of low pressure in the Northern hemisphere is constantly deflected to the right, and therefore air circulates round an area of low pressure in a direction opposite to that in which the hands of a clock travel, and out of an area of high pressure in the same direction as the hands of a clock, whilst in the Southern hemisphere it will (being deflected always to the left) flow into an area of low pressure in the same direction as the hands of a clock travel, and out of an area of high pressure in a direction opposite to that in which the hands of a clock travel.* Buys Ballot, of Utrecht, enunciated the result of these observations in the following law, viz., " Stand with your back to the wind, and the area of the lowest pressure will always be on your left in the northern hemisphere and on your right in the southern hemisphere. The velocity of the wind in relation to the pressure it is capable of exerting has been expressed by Colonel Sir H. James, R.E., F.R.S., as follows: V 2 x '005 - P. Where V = velocity in miles per hour, ,, P = pressure in pounds per square foot. Wind is measured by means of instruments called anemo- meters, some of which indicate the velocity of the wind from which the pressure exerted can be estimated by means of Colonel Sir H. James' formula given above, others indicate the pressure of the wind directly. It is recorded that Sir Isaac Newton as a boy attempted to estimate the force of a gale of wind which occurred on 3rd September, 1658, by jumping, first, in the direction from, and next, in the direction towards which the wind was blowing. One of the earliest wind gauges consisted of a swinging rectangular plate, similar to the old signs which at one time swung on hinges from a horizontal bar in front of shops and inns, of late years in front of inns only. The angle which the swinging plate made, with the horizontal bar supporting it, indicating the force of the wind. An instrument of this kind, but fitted with a vane so that the plate is always broadside on to the wind is still employed in Russia (Wild's), which exposes an area of about 72 square inches (15 x 30 centimeters) and weighs about 6'8 ounces. With Wild's gauge the wind can be fairly accurately measured up to force 8 Beaufort scale, which equals a velocity of about 48 miles per hour, i.e., a fresh gale. * Air flows into an area of low pressure in a direction which is inclined to that of the isobars at an angle of about 20 degrees. 259 With a gentle breeze, having a velocity of 18 miles per hour, the angle of displacement from the vertical is about 45, and with a velocity of from 44 to 45 miles per hour it is about 8o. Lind's anemometer which appeared in 1775, consisted of a U shaped tube, one arm of which was bent over at right angles, and the whole apparatus balanced and fixed to a spindle in such a way that by means of a vane attached to it the horizontal arm always directly faced the wind. The U tube contained fluid, and the height to which the fluid was driven up the closed vertical arm of the apparatus was a measure of the velocity of the wind. Dine's portable pressure anemometer resembles Lind's instrument in that it consists of a U shaped tube containing fluid, and one arm is bent at right angles to the ascending part of the limb, but differs in the following respects, the other limb of the U tube is open, and the instrument is held in the hand and pointed to the wind when required for use, instead of revolving round on a spindle. Also the whole isntrument is enclosed in a metallic case, from which the horizontal limb projects as a metal arm, and before use the instrument is drawn out like a telescope and fixed when fully drawn out by means of a bayonet-joint. In order to avoid the error which arises from the wind moving in a direction not horizontal and, therefore, not tangential to the open vertical arm of the ap- paratus, this end is enclosed in a metallic cylinder pierced by a ring of holes. On page 170, vol. xviii.. of the quarterly journal of R. Met. Soc., Dine, when describing the head of a tube anemometer which he has designed and employed extensively in his researches on wind velocity says, that the vacuum pro- duced by the wind blowing over the mouth of an open tube has been shown to be dependent on the exact perpendicularity of the tube, but if the open-mouth of the tube be enclosed in a cylinder, closed at the top, and having a ring of holes around it, a partial vacuum is formed when the wind passes over the holes which is not subject to the objection referred to in re- gard to the mouth of an open tube. The variety of anemometer most commonly employed is Robinson's, this consists of four hemispherical cups, each ri2 feet apart, and each having a diameter of three inches. The cups are connected by rods which cross at right angles, and each pair is so arranged that one looks in one direction and the other in the direction opposite, the result is that when any one cup reaches any given point it always pre- sents the same aspect to it, so it comes about that the concave side of one of each pair of cups is always more or less facing 260 ongoing with the wind, and the convex sides of the other two will be approaching or going against the wind, and since, by reason of their shape, there is greater pressure on the concave than on the convex side, the cups revolve, and always in one direction, from left to right. Fig 69 ROBINSON'S ANEMOMETER. Since each pair of cups is 1*12 feet apart, the circle des- cribed by them will be _22 x i''i2, which = 24-64 or 3-52 feet. Dr. Robinson, who designed this instrument, assumed that the cups revolve with 3 the velocity of the wind. Numerous experiments have shown that this faclor is too great, as it revolves with a velocity nearer to that of the wind, so that really it should be between 2 and 2'2y. Dines says that "probably for a steady wind the higher value is best, but for a gusty wind the lower value, viz. : 2*00 is correct/'* * Dine's Anemometer Comparisons, p. 183, Vol. XVIII., 1892, Q. Journal of R. Met. Soc. 26 1 Employing the original factor one complete revolution indicates 3-52 x 3 = 10-56 feet of air movement, which means that five hundred revolutions indicate one mile (500 x 10^56 = 5280 feet = 1760 yards). The mechanism is as follows : On the shaft supporting the cross-bars bearing the cups is an endless screw, which works into cog-wheels geared so that the instrument is made to show the number of miles travelled by the wind, and if the observation be reduced to a specified time the velocity of the wind in miles per minute, hour, or other period of time can be determined, the wheels cause a dial and pointer to revolve, and on the dial are two circles, the outer showing miles and tenths of a mile up to five miles, and the inner showing spaces for five miles, one complete revolution of the dial moves the pointer through one space on the centre or inner circle, and this inner circle is graduated up to 500 miles. When 500 miles have been travelled the pointer, if it was originally at o, will have travelled through 100 spaces, and after it has travelled another five will once more be at o. After our observations have been made, at the end of 24 hours it is usual to set the pointer at o, but in some instruments the pointer cannot be so set, and the reading has to be noted and the next observa- tion made by deducting the previous observation from it, as in reading a gas-meter. It is most important that Robinson's anemometer be kept clean, well-oiled, and placed in an exposed position at least 20 feet from the ground. * Wind never blows continuously, and it is most unevenly distributed. This is very noticeable if observations are taken with a pressure anemometer ; even when the wind appears to be blowing most steadily, an anemometer shows that it comes in gusts, and the pressure and velocity never remain uniform for more than a few seconds. The destruction wrought by a storm is most irregular, great damage is often done to certain buildings in a street, whereas others escape without the loss of a tile, yet these same houses are apparently equally well- built and equally exposed. Examples of damage done by storms in this irregular manner must be familiar to all. The force of the wind is recorded in ships' logs and in meteorological reports according to the Beaufort Notation, which was drawn up by Captain, afterwards Admiral Sir Frederick Beaufort, when in command of H.M.S. Woolwich, in 1805, viz : * In placing anemometers or taking observations on the force and direction of the wind, the instruments must be placed in exposed positions where no errors can be caused by deflection of the wind by trees or buildings. 262 BEAUFORT NOTATION TO INDICATE THE FORCE OF THE WIND. 1 1 Beaufort Scale in words. Mean velocity in miles per hour Mean pressure in Ibs. on the sq. foot. Calm 3 I Light air Just sufficient to give steerage way 8 5-0 oz. 2 Light breeze With which a well 1-2 knots conditioned man-of- 13 i3'5 .. 3 Gentle ,, war under all sail -1 3-4 and clean-full, would 18 1-6 Ibs. 4 Moderate,, go in smooth water 4-5 ,, 23 2-65 5 Fresh In which the same ship could just carry close-hauled Royals, etc. 28 4'0 6 Strong ,, Single reef top-gallant sails 34 5'75 .. 7 Moderate gale Double reef jib, etc. 40 8-0 8 Fresh Triple reef courses, etc. . . 48 ii-5 - 9 Strong Close reef and courses 56 157 .. 10 Whole gale With which she could only bear close reefed main top- sail and reefed fore-sail . . 65 21'2 ,, n Storm With which she could be re- duced to storm staysails . . 75 28-2 12 Hurricane To which she could show no canvas 80-100 31 -49 to 49'2 The direction of the wind is determined by a vane. This may consist of a cone of bunting attached to a grummet and connected by four strings to a stick, or it may consist of an arrow with the tail spread out, revolving round a vertical axis, friction being reduced to a minimum by keeping it clean and well oiled. Waldo, in his Modern Meteorology, page 101, says, the first weather-cock on a church spire was set up in the year 820 on a church in the Tyrol, and that the regular observation of wind vanes for meteorological purposes was not begun till 1650 in Italy, and until a few years later in England. The direction is recorded according to the points of the compass, and its direction described as from a certain quarter, not as in the case of ocean currents, where the direction towards which they flow gives the name. 26 3 The points of the compass may with advantage be given. It is not usually necessary to describe wind direction more ac- curately than to the half-cardinal, or possibly to the false points. The cardinal points are four in number, N, R, S, and \Y. The half-cardinal are between these, and we have NE, SE, SW, and NW, being four in number. The false points or three letter points are midway between the cardinal and half-cardinal, and consist of NNE, ENE, ESE, SSE, SSW, WSW, WNW, and NN\Y, eight in number. Whilst between the half-cardinal and false, and between false and cardinal come the by-points, thus : N by E, NE by N, NE by E, E by N, etc., sixteen in number. Four cardinal, four half-cardinal, eight false points, and sixteen by-points. The total 32 being the number of points into which the compass is divided, and since the entire circle comprises 360 degrees, it follows that each point is distant from the next 11 1 5', or in other words, the difference of a point in taking a bearing of an object amounts to 11 15 . The knowledge of some of the ways of finding the north in the absence of a mariner's compass, might be useful at some time to one, whether for determining the direction of the wind, or possibly for shaping his own course in some particular direction, so we will mention briefly a few ways. A vertical pole erected anywhere throws a shadow which decreases in size from sunrise to noon, and lengthens from noon to sunset : if we know the true local time, we can always find the points of the compass by observing the shadow ; thus at noon, local time, in the northern hemisphere the shadow will be shortest and fall towards the N., at 9 a.m. it will fall N.W., at 3 p.m. it will fall N.E. In the southern hemisphere, since the sun is north, at noon the shadow will fall S., at 9 a.m. S.W., at 3 p.m. S.E. Local time, since the introduction of railways, has been lost sight of, but local time is that which is shown by a properly corrected and properly set sun-dial. Since the earth rotates once in 24 hours, it follows that it must always be noon somewhere ; in other words, the sun appears on every meridian in succession. (Meridian being the term applied to an imaginary line run- ning north and south drawn through any place, because the sun crosses this line at mid-day. Lat. meridies=mid-day). The circumference of the world being divided into 360 degrees, the rate of angular rotation is therefore 360 degrees for 24 hours, i.e., '\ = \" which means that for every 15 going west noon will be one hour later, that is to say 15 per 60 minutes, which = i per four minutes, so that at any place i west of a given meridian, local time will be four minutes later at that place than at the meridian in question. Going round the world then in a westerly direction in 100 days, the traveller 264 would only see 99 noons, because each day would be one per cent, or 14 minutes 24 seconds longer than a day at home. In order, therefore, to prevent confusion in dates when the 180 meridian is crossed, the calendar is put on two days, i.e., one diy is missed ; and in going round the world in an easterly direction, he would see 101 noons, each day being one per cent, shorter than a day at home, and he would have 101 days doings to record : so that in crossing the 180 meridian, the calendar would have to be put back by showing two successive days as the same date. If one has a watch showing correct local time, one can always find the north or south by the following simple rule : In the northern hemisphere, if we point the hour hand to the sun, the spot midway between that point indicated by the hour hand and twelve o'clock (going forwards on the watch before noon, and backwards after noon) will point due south. Take the case of the equinoxes as giving the most obvious proof; we know r that the sun rises in the east at 6 a.m. on these occasions, and that if we point the hour hand to the sun, midway between 6 a.m. and 12 will be 9; a line drawn through o will then indicate the direction of south. Again, take the case of the sunset at the equinoxes ; we know the sun sets in the west at 6 p.m., so if we point the hour hand to the sun and follow the rule given above, 3 o'clock will indicate south. In the southern hemisphere, of course, these directions show us north. We have given details as to determining the direction and force of the wind, we next have to consider the effect of prevailing winds on health. Many places which otherwise would be well nigh unendurable, become not only habitable, but perfectly healthy, owing to the beneficent action of the Trade winds, which are permanent winds blowing between the tropical and the equatorial calms. At the tropical calms there is an area of high pressure and at the equator an area of low r pressure arising from the heating and consequent expansion of the air, which, as a result of expansion, rises in the upper regions of the atmosphere over the tropics, and causes areas of high pressure and calms at the tropics of Capricorn and Cancer. In the northern hemisphere the " Trades " being deflected to the right as already explained, appear as N.E. winds ; in the southern hemisphere they appear as S.E. winds being deflected to the left. These winds follow the sun ; as the sun goes north, the S.E. trades are taken across the equator and appear as the S.W. monsoon, w r hich is a hot moisture-laden wind ready to part with its moisture if 265 exposed to cooling influences ; conversely, when the sun goes south the Trade winds follow it. The N.E. Trade crossing the equator appears as the N.W. monsoon in regions south of the line, and like the S.W. monsoon is a hot moisture- laden wind. Monsoons in various parts of the world are produced on a large scale, extending over longer or shorter periods, exactly as land and sea breezes are produced; they are due to heating and consequent expansion, alternating with cooling and consequent contraction of the air over the land, and it is the areas of low pressure formed under these con- ditions on a vast scale which produce in many parts of the world periodic winds called monsoons. The larger the conti- nent the greater will be the monsoon action, and if, in addition, there are lofty mountain ranges to form, as it were, a shaft which conducts the heated air in an upward direction, then it will be very marked, as in India. The word monsoon is derived from an Arabic word mansim, a set time or season of the year, and it is because these winds appear at certain definite seasons that they are known as monsoons. Many people attach considerable importance to winds being set in motion not by the diminished pressure exercising an extractive action, so much as the increased pressure, causing the air to flow into areas of low pressure. A sea- breeze commences first by air pressure being greater over the sea than over the land, and, conversely, a land breeze commences by the colder and denser air over the land flowing out to equalise the pressure where pressure is less over the sea. Fohns are peculiarly oppressive hot blasts which are felt in different parts of the world. The cause of the Fohn is this, wind is forced to ascend a mountain range, on the weather- side where it is a cold moisture-laden wind, but when it has been deprived of its moisture and warmed by the latent heat given out in the act of condensation, it appears on the lee-side as a hot dry wind ; a good example of such a wind is the nor'- wester in New Zealand, which is so unpleasant to the dwellers on the Canterbury plains to leeward of the New Zealand Alps. Winds exercise very great influence on health, the evil effects of the cold British east wind are due to its peculiar chilling power, which is partly owing to its being dry and so favouring evaporation and causing a reduction of temperature, and partly also because it is cold through having passed over the large tracts of ice and snow on the Continent of Europe. [ 'in iations in Atmospheric Pressure. We have already alluded to isobars as lines connecting places where the barometric pressure is equal, and we have 266 also spoken of barometric gradients, and how r the force of the wind is dependent on the steepness of these gradients. We now have to speak of Variations in Atmospheric Pressure. These are divided into Regular and Irregular. Regular are divided into Diurnal and Annual. Irregular into Cyclones and Anti-cyclones. The Diurnal is seen best in the Tropics, and to a very slight extent in temperate climates. Every day two atmos- pheric waves pass over the earth, when the crests of these waves are over a place we have the maximum pressures, and when the troughs, we have the minimum pressures ; the two maxima occur about loa.m. and 10 p.m., the two minima about Fig. 70 SOME ARRANGEMENTS OF ISOBARS (after Abercromby}. 3 p.m. and 3 a.m. These variations in pressure are most notice- able in the tropics, because there, temperature (the prime cause) is high, and also because there, the variations are less likely to be masked by the irregular variations described later on. The first maximum is thought to be due to a gradually increasing temperature which, up to this hour, has caused the air to expand but as yet to an insufficient extent to enable it to over- flow in the upper regions of the atmosphere. The second maximum is due to increased density of the atmosphere, the result of the cooling of the air ; the first minimum at 3 p.m. or 4 p.m., is due to the air about that time being at its minimum density, owing to the effects of heat which have caused the air to expand and flow away to the east, from the hemisphere exposed to the sun ; the morning minimum at 3 a.m. is not so marked as the afternoon one, and is thought tobe due to the cool- ing of dust particles and condensation on them of the aqueous 26 7 vapour up till now present in the air ; the removal of aqueous vapour causes a diminution of pressure, and at the same time the air is warmed by the latent heat set free during conden- sation. The Annual variations are readily explained, where the air is hottest the pressure will be least, consequently, we have high barometric pressure over land in winter, and low over the sea in that period, and vice versa in summer. The irregular variations are Cyclones and Anti -cyclones. Cyclones are moving areas of low pressure moving generally from a westerly to an easterly direction, with varying rapidity. In cyclones, the lowest pressure is in the centre, and isobars when plotted on a chart assume, as a rule, a more or less circular form, hence their name. The isobars are generally close together, i.e., the gradients are steep, and the winds circulate round an area of low pressure in accordance with Buy's Ballots Law, i.e., in a dire6lion against the hands of a watch in the northern hemisphere, but in the same direction as the hands of a watch in the southern hemisphere, so that if a ship under sail enters an area of low pressure, and the barometer is observed to be falling, it is evident that the ship is on that tack which will take it into the centre or vortex of the dis- turbance ; on drawing a rough diagram, illustrating this B/U.& Bl ue Refraction St ra to \-CumuL \HardSky REAR VV//?r/K Cirrus Fig. 71. CYCLONE PROGNOSTICS (after A bercromby ).* * Popular Weather Prognostics, by the late Hon. Ralph Abercromby, F.M.S., and William Marriott. 268 circulation of the wind, it is seen that if the sailing ship proceeds on the port tack it will, in the northern hemisphere, get into the dangerous zone, but out of it if sailing in the southern hemisphere ; whilst if the ship be on the starboard tack in the northern hemisphere it will sail out of the area of low pressure, but the same tack in the southern hemisphere will take it into the area of low pressure. When a cyclone is approaching, the barometer is seen to fall, and the temperature to rise, the wind increases, and the sky becomes cloudy, finally rain comes, followed by a clearing sky; the rain ceases, the wind changes, and the barometer once more commences to rise, unless another area of low pressure succeeds it, as is often the case. When a cyclone passes away, if the observer is situated on the south side of the centre of low pressure, as soon as the centre is passed the wind veers or changes with the sun, but if we are to the north of the centre it backs or goes against the sun ; backing of the wind indicates, as a rule, further continuance of the storm, whilst veering indicates an abatement, simply because these disturbances, as a rule, pass to the north of us. Thus, a cyclone BLUE SKY REAR Fig 72 WEATHER IN A CYCLONE, Nov. i4th, 1875 (after Abercromby). * * Popular Weather Prognostics, by the lake Hon. Ralph Abercromby, F.M.S., and William Marriott. 269 passing to the N. of a place first brings to that place a south wind, then S.W., W., N.W., N. : whilst if it passes to the S. of a place, it brings first a S., then S.E., E., N.E., and N. wind. The speed at which cyclones travel is generally about 20 or 30 miles per hour in England and the west of Europe, but in America, where the cyclones are more pronounced, the speed is greater. The difference between a cyclone which unroofs houses, wrecks ships, and one which brings merely changes of weather, is one of degree rather than of kind. Secondary cyclones are, as it were, subsidiary areas of low pressure springing out from the parents, in them the iso- bars are looped and not completely concentric. V-shaped de- pressions are areas of low pressure thrust in between areas of high pressure. Anti-cyclones are irregular areas of high pressure in w r hich the isobars are far apart, or in other .words, the gradients are very gentle ; anti-cyclones are almost stationary, and sometimes these conditions of pressure remain over a Cold Air WEA THER Frost */ Fig 74 STRAIGHT ISOBAR PROGNOSTICS. 2 7 I CHAPTER VI. ATMOSPHERIC ELECTRICITY. The air is always more or less charged with free electri- city, and is usually positively electrified except within a few feet of the earth ; sudden changes of state of aqueous vapour, and more especially extensive and rapid evaporation produce changes in the electrical condition of the atmosphere. Under a cloudy sky the air may be positively or negatively electrified, but the earth is always negatively electrified If from some cause or another a cloud, or clouds, over- shadowing the earth become highly electrified with different signs, or with signs different to the earth, if they are suffi- ciently electrified a disruptive discharge will occur either bet wren the clouds if they are oppositely electrified, or in turen the clouds and the earth, this discharge, which is lightning is intensely luminous, and this is due to the par- ticles in the air traversed by the flash being heated to incan- nce. If the discharge' takes place through a tree, the tree will split, the cleavage being due to the sudden heating of the sap, the moisture of which is suddenly converted into steam. If the discharge takes place through a moderately good, but yet insufficiently good conductor, such as a chimney stack, the 'intense vibration caused by the resistance of the particles will cause it to fall, or possibly any moisture con- tained within its interstices will be converted into steam, and the chimney stack or building will be shattered. The sudden and intense heating of the air through which the spark passes will cause it to expand suddenly, and this contracting again with equal rapidity produces thunder ; the sound is caused by the setting in m'otion of air-waves which, echoing from cloud to cloud, and reaching the earth from different portions of the flash at perceptibly different intervals of time, produces the roar resembling a volley of musketry, or the booming of can- non. Sound travels slowly, viz., at the rate of 1,100 feet a second,* whereas light travels at about 186,000 per second, the This is the rate when the temperature of the air is 32 degrees F., every increase of i degree F. in temperature accelerates the rate by 2 ft. a second. 2 7 2 flash is therefore seen before the thunder is heard, the interval depending on the distance, thus if the sound is heard, say, five seconds after the flash is seen, the flash has occurred about 5,500 feet off, or rather more than a mile away. Thunderstorms occurring more than fifteen miles away cannot be heard, but the flash is visible in the sky. One of the dangers in a thunderstorm is that known as return shock which may be attended with fatal consequences. This is an inductive phenomenon caused by an overhanging highly electrified cloud ; as soon as the discharge has taken place between the cloud causing the induction and another cloud, or with the earth, the electricity induced in the body returns to earth. Return shock is by no means always fatal, and the disturbance which many nervous people feel during a thunderstorm may, in many instances, be attributable to mild shocks of this kind. When telephone gongs ring during thunderstorms, it is the return shock which is the cause. Lightning conductors are metal rods attached to the highest points of buildings or to the masts of ships ; to be efficient they must be made of sufficient size and good conducting metal such as iron or copper, and this must lead into moist earth or the sea. A light- ning conductor depends for its action on induction or the power possessed by pointed objects to carry off from the body to which they are connected the opposite kind of electricity to that possessed by the body causing the induction, in other words it tends to equalise or reduce to a minimum differences of potential between the clouds and the earth. Thus, if a positively electrified cloud be hanging over the earth in a situation where there is a conductor, negative electricity is attracted to the point, and its tension being sufficient to overcome the resistence of the air it flows off to the cloud neutralising or tending to neutralise it. A lightning conductor protects a conical space, the radius of the base of which is about double its height. St. Elmo's Fire is a luminous electrical discharge, occa- sionally seen at the yard-arms or mast-heads of ships, it is simply due to induction ; air positively electrified, inducing negative electricity to pass off and combine with a brush-like series of sparks from pointed extremities such as we mentioned. Aurora is an electrical phenomenon caused by electrical discharge occurring at great altitudes in rarefied air free from moisture, it is known as Aurora Borealis in the Northern, and 273 Aurora Australis in the Southern hemisphere, and is seen only in high or moderately high latitudes ; the positive elec- tricity in the upper region of the air is thought in these cases to be due to the effects of the sun causing evaporation from the sea, and overflow of air at great altitudes in the tropics, the overflow differently electrified, eventually arriving at the polar regions. The appearance of the Aurora or Northern Lights is familiar to many, but in Europe it is chiefly those who dwell or have visited places between latitude 66 and 75 who have seen it at its best, the appearance is that of an arch or crown of light, from which bright streamers of fire shoot upwards with a pulsating movement, the arch appears to be very high up, and is situated over the magnetic pole. 274 CHAPTER VII. CLIMATE. Climate is a word used to denote the prevailing conditions of the atmosphere over a portion of the globe as regards temperature and relative humidity. The factors which take part in the formation of any particular climate are often very numerous, and these will be considered in turn. The word climate is derived from the Greek word /cAi'/m (a slope), because it was thought at one time that the angle at which the sun's rays strike the earth in different latitudes was in itself sufficient to account for all the various climates. Latitude, as we shall see, is undoubtedly the most important factor, but its influence may be considerably masked by other circumstances. Dr. Henry Bennett * divides climates into five groups : (i). Warm Climates, which include the equatorial, tropical, and sub-tropical regions, \vhere there is (as a rule) heavy rainfall, high temperature and dry and rainy seasons. (2). Temperate Climates, showing a wide annual range of temperature, rainfall chiefly in autumn and winter, and a mean temperature of between 50 and 60 degrees F. (3). Cold Climates, with long winters, short summers, and " rainfall." chiefly in 'the form of snow. (4). Marine Climates, characterised by an absence of extremes of temperature, rainfall abundant and fairly evenly distributed throughout the year. (5). Mountain Climates, in which the chief features are : Low barometric pressure, extremes of temperature, excessive solar and terrestrial radiation, as a result of in- creased diathermancy of the air caused by the small amount of dust particles and aqueous vapour present. To these we might add another type, viz. : Continental, which consists in extremes of heat and cold prevailing over large inland tracts of country, according to whether it is summer or winter. The factors in the production of climate are: (i) Latitude; (2) Altitude ; (3) Configuration of the land ; (4) Proximity * Quoted by Dr. C. Theodore Williams in Treatise on Hygiene, Vol. I., p. 203. 275 of the sea ; (5) Position in regard to high hills or mountain ranges ; (6) Prevailing winds ; (7) Rainfall ; (8) Vegetation ; (9) Soil. If we now consider these in turn we can judge of their relative importance. (i). Latitude : It is evident that the more vertical the direction of the sun's rays the greater will be their heating power, because a beam of light falling perpendicularly on to a surface strikes a smaller area than when it falls obliquely ; * in addition it travels through a shorter distance, and since the lower strata of the atmosphere contain a large amount of heat absorbing materials it follow r s that the shorter the distance which the sun's rays travel through these heat absorbing strata the less will be the loss. The Sun in his apparent journeyings appears vertically over every portion of the Torrid Zone twice in the year, but outside this zone the sun is never vertical, at the Summer Solstice (2ist June) the meridian altitude of the sun at places in the Northern hemi- sphere is equal to the complement of the latitude plus 23 27' 44" (by complement of the latitude is meant 90 minus the latitude), whilst in the Southern hemisphere on 2ist June the meridian altitude at any place is equal- to the complement of the latitude minus 23 27' 44"; at tne Winter Solstice (2ist December) the above conditions are reversed. At the Equi- noxes (2 ist March and 23rd September) day and night are equal all over the world, and the intensity of solar radiation is inversely proportional to the latitude, the higher the latitude the less the amount of solar radiation received. A considera- tion of the above facts will readily explain the important part that latitude plays in the formation of climate. (2). Altitude : The importance of altitude in the produc- tion of a climate is shown by the fact that as one ascends lofty mountains in tropical countries the climate varies as we ascend, which materially affects the nature of the vegetation, so that a mountain sufficiently lofty, in the equatorial region, to have a portion of it covered by perpetual snow, would show zones of vegetation at various heights, corresponding with that experienced in every latitude from the equator to the poles ; the snow line (corresponding with the arctic regions) at the equator is above 16,300 feet. The reason for * To prove this, take an ordinary sheet of ruled paper and draw two sets of parallel lines of equal breadth between two of the ruled lines, one set being drawn perpendicular and the other at an angle to the ruled lines, now compare the breadth of the areas covered ; expressed mathematically, the area which a beam of sunlight will cover is in inverse proportion to the sine of the obliquity. the fall in temperature with altitude is, that air is more or less diathermanous according to whether it contains little or much aqueous vapour and dust particles, consequently it is scarcely heated at all by the passage of the sun's rays through it in the higher regions of the atmosphere, and is only warmed by the obstructions to the sun's rays just mentioned and contact with the warm earth where it becomes warmed by convection; the higher we ascend the less is the pressure to which the air is subjected and consequently it expands more and more as the pressure diminishes, but by this expansion work is done against gravity and therefore heat is consumed. If the air were dry then the fall in temperature would amount to i F., for every 180 feet of ascent, but as a matter of fact the air is never quite dry, so that the fall of temperature w r orks out to about i F. for every 300 feet, the latent heat given out on the condensation of water vapour which occurs as the air is cooled, counterbalancing to a certain extent the amount of heat used up in the work of expansion against the attraction of gravity. (3). Configuration : The nature of the surface of the land, whether flat or hilly, plays an important part in modifying the climate of a place ; places where the slope of the land faces the sun at noon will enjoy a much warmer climate than those in the same latitude, the slope of which looks away from the sun. Hills or mountains may modify the climate by setting up currents ; on a level plain under the influence of a strong sun the air will be heated and rise en masse, but where there are hills these will act like a chimney, by creating a draught and thereby cause powerful currents to be set up. Again, if a place be situated low down between hills, the air imme- diately over it will often be colder than at other places higher up on the hillsides, because the. colder and denser air flows down the hills and remains like water in a hollow, thus displacing the warmer and lighter air, which is driven upwards. (4). Proximity of the sea; Continental places near the sea and small or moderate sized islands enjoy a climate which is tempered by the presence of water, which having such high specific heat is slowly warmed and slowly cooled, and so effectually prevents rapid or extensive changes of temperature. Then again the air in places near the sea contains more aqueous vapour than does the air over inland places far removed from large expanses of water, this aqueous vapour then exercises its action as a screen in checking solar and terrestrial radiation ; in inland places, where the air is dry or containing little aqueous vapour, the absence of this screen gives rise to extremes of heat and cold, which has already 277 been alluded to when speaking of the " continental " type of climate. Ocean currents flowing along a coast may modify the climate considerably. Both warm and cold currents are met with in various parts of the world ; as an example of the former we may mention the Gulf stream, which so markedly softens the climate of the west coast of Europe ; as examples of cold currents we may mention the cold Labrador, or Arctic current, and the South Equatorial current. The Arctic current flows out of Davis Strait, over the Newfoundland Bank, and down the east coast of N. America, between it and the Gulf Stream. The difference in temperature between these two currents is considerable, in the early part of the year it may amount to 30, and from 25 to 15 during the warmer months. It is owing to this cold current that the climate of the east coast of Canada is so cold and damp in winter and so bracing in summer. The other example of a cold current which we mentioned is that known as the Peruvian, or Humboldt current, which from 4OS. runs to the northward along the west coast of S. America as far as the Bay of Panama, where it merges into the South Equatorial current, which flows past the Galapagos Islands, the climate of which it affects most favourably, giving them a cooler climate than other places situated on the equator. (5). The proximity of Hills or Mountains : When hills or mountains are present of considerable height and perpendicular to the prevailing winds their influence on climate will be very marked ; the climates on the weather and lee sides of these hills will be quite different ; places on the windward side will have a heavier rainfall than those on the leeward side, because condensation will occur when winds laden with water- vapour reach the hills. Condensation occurs for two reasons : the moisture-bearing winds are cooled to a temperature below the point of saturation by a6lual contact, and secondly, they are forced to ascend and so suffer further loss of moisture, due to the expansion of the air under diminished pressure, which causes, as we have previously shown, a fall in temperature and condensation of water vapour as a consequence. On the same side of the hills the weather will frequently be cloudy and rainy, whilst on the other side it will be drier and brighter, there will be fewer clouds to obscure the sun, and there will be more radiation giving colder winters and warmer summers. It would seem hardly necessary to say that the wind which flows over the hills, after being depleted of aqueous vapour, descends and becomes in consequence warmed, the conditions being the converse of those described when speaking of the cooling of air as the altitude increases. 2 7 8 (6). Prevailing winds : The effect of winds on climate is very great ; it is not difficult to rind examples of places in the same latitude where the climates are quite different, simply because the prevailing winds have been subjected to different conditions before they reach that place ; for instance, a wind which has its origin in an overflow from the same area of high pressure into one of low pressure, may have travelled to one place over a sandy desert and to another across a sea, in the one place it will be felt as a drying wind, which in no way interferes with solar or terrestrial radiation, whilst in the other, as a moist wind, it will effectually act as a screen to radiation. If this occurs in low latitudes the disadvantages of a steamy atmosphere can scarcely be over-stated. By studying the map we can explain the cause of the direction of the prevailing winds by noticing the distribution of land and water in the region in question, for we know that areas of low atmospheric pressure are formed over the land in summer, and over the sea in winter, with high pressure over the sea in summer, and over the land in winter, and that air will, as already stated, flow into the low pressure areas from those having higher pressure at an angle of about 20 to the isobars, unless there are some physical conditions, such as a range of mountains in the region under consideration, which will set up currents and so cause a divergence from the course the winds would naturally follow. In selecting places for sanatoria the direc- tion of prevailing winds should influence one more than anything, since it has recently been shown how great an influence prevailing winds have on the mortality rate for phthisis. (7). Rainfall : Some places, for example, like the west of Ireland, owe their peculiar mildness of climate to the large amount of rain which they receive ; warm moisture-laden winds coming over the sea lose much of their vapour when they come in contact with the colder earth and the condensa- tion which brings about this loss sets free a great deal of heat, which to a large extent compensates for the loss due to the interception of sunshine by the clouds which the warm, moist, rain-bringing winds must give rise to. It is more important when considering the climate of a place to know the number of rainy days than the actual rainfall ; a place with a heavy rainfall might enjoy a warm, dry climate during the greater part of the year, whereas another place, the rainfall of which was slight, might be cold and damp, and suffer from a want of sunshine, because at that place there were so many rainy days, that is to say, days on which the actual rainfall may have been slight, but which were cloudy and therefore sunless. 279 (8). Vegetation : The presence or absence of vegeta- tion affefts climate considerably ; where vegetation is scanty the air will, as a rule, be dry and subject to extremes of temperature, many such places having undergone a complete change of climate after extensive tree-planting. Forests act chiefly in affording a screen to the wind, and in valleys where the hills are covered with trees the downflow of cold air is interfered with and the cold air distributed, so preventing the formation- of the cold stratum so often found in valleys where there are no trees. The climate in large forests is more equable than in the open country, although evaporation proceeds extensively from the leaves of trees, yet the shade afforded by them and their mechanical action in checking air movement retards evaporation from the soil and more than counterbalances that from the leaves, so that the air in forests is always humid, and it is also cooler in summer and warmer in winter than out in the open. (9). Soil : Soils which permit of good natural drainage will tend to make a climate warmer and more agreeable than those retentive of moisture. The air over soils readily drained will be dry, and the soil will .become more readily heated because it is not chilled by the process of evaporation in the way that a moister soil is. The colour of the soil is an important faclor ; where this is dark it will absorb much more heat than where it is light coloured. Sand is very retentive of heat, but since the air of sandy soils is drier than over heavy soils, where clay is abundant the heat retaining property of sand is to a great extent compensated by the increased diathermancy of the air over it, which allows a greater amount of terrestrial radiation to take place. Soils which from their closeness do not allow the water to sink in, or run off, give rise to a cold climate, this is particularly the case with clayey soils, which become heated very slowly and consequently from the amount of moisture they hold, the air over them is always cold and damp, with the disadvantages attending diminished diathermancy. 280 APPENDIX (A). HYGROMETRICAL TABLES (GLAISHER). I. TABLE OF FACTORS. Reading of the Dry-Bulb Thermometer. 20 degrees 21 ,, 22 ,, 23 ,, 24 j 11 jj jj 27 ,, 28 jj 29 jj 3 jj 32 j> 33 jj 34 jj 35 jj 1 jj jj 39 j> 40 jj 41 jj 42 jj 43 ,, 44 " 46 JJ 47 JJ 48 JJ 49 J1 50 52 II 53 J, 54 J) 55 ,, Factor. Reading of the Dry-Bulb Thermometer. 8-i 4 56 degrees 7-88 57 jj 7-60 58 7.28 59 tt 6-92 60 }J 6'S7 61 6'08 62 || 5'6i 63 M 5-12 64 jj 4-63 1 jj > j 3' 70 67 68 j j 3-01 69 > j 277 70 jj 2-60 ,, 2-50 72 ,, 2-42 73 ,, 2-36 74 ,, 2-32 75 ,, 2-29 76 ,, 2*26 77 ,, 2-23 78 M 2'2O 79 J) 2-18 80 2-16 81 2-14 82 H 2.12 83 ,, 2'10 84 Jj 2'08 85 jj 2'06 86 j j 2'O2 88 2'00 89 1-98 90 Factor. I-87 1-86 1-85 1-83 1-82 r8i i -80 1-79 r 7 8 1-77 r 7 6 1-72 171 170 1-69 r68 r68 1-67 r67- r66 1-65 '65 1*64 1-64 1-63 1-63 1-62 28l TABLE II. TENSION; or Elastic Force of Aqueous Vapour in inches of Mercury for every degree of Temperature from o to 90. Temperature. o degree 9 10 ii 12 13 14 \l '9 20 21 22 23 24 2 7 28 29 30 3 1 32 33 34 P degrees Tension. Temperature. 044 39 degrees "046 40 ,, 048 4i ' ,, '050 42 ,, 052 43 ,, 054 44 057 45 ,, 060 46 ^ 062 47 tt 065 068 48 49 071 5 ,, 074 7 8 52 " 082 53 Jf 086 54 ,, 090 55 ,, 094 56 n 098 57 ,, 103 58 ,, 113 123 129 135 141 147 153 167 174 iSi 188 196 204 '212 220 229 6l 62 * 3 64 6 9 7 7 1 72 73 74 % 11 Tension. 247 257 267 277 288 299 323 '335 348 3 6l '3 403 418 '433 '449 465 482 500 '537 556 576 639 66 1 .708 733 "759 785 812 840 868 897 927 282 Temperature. 78 degrees 79 81 82 83 4 8s Tension. 958 990 1*023 ! '57 1-092 1*128 1-165 1*203 1-242 Temperature. 87 degrees 88 89 i 90 9-2 93 94 95 Tension. r282 1*410 i '455 1*501 i-548 1-596 1*646 APPENDIX (B). CHARACTERISTICS OF CLIMATE MET WITH IN SOME BRITISH POSSESSIONS. AUSTRALASIA. SYDNEY, N.S.W. Latitude 33 51 '41 " S. The mean annual temperature is 63 F, During the summer months, December, January and February, the weather is hot and steamy, with a mean temperature at noon of about 80 ; hot winds from the N.W., known as Brickfielders from their pecu- liar parching 1 dry heat are experienced from time to time during these months, and are followed, as a rule, by cold winds, called Southerly Busters, which come on very suddenly and bring with them clouds of dust which penetrate everywhere, these winds are very violent, the velocity varying from 40 to 70 miles an hour, and even 90 miles an hour has been recorded. When these winds commence to blow the fall in temperature is very rapid, a drop of 20 being by no means uncommon ; their usual termination is a thunderstorm and heavy rain. The annual rainfall which occurs, chiefly between February and June, amounts to about 49 or 50 inches, falling on about 157 days. MELBOURNE. Approximate Latitude 38 S., in Victoria, has a mean annual temperature of 58'o and a climate which is very agreeable ; the air is much less humid than in Sydney, and the rainfall averages about 25'85 inches or a little more than half that of Sydney. ADELAIDE. Approximate Latitude 35 S. in S. Australia enjoys a dry climate, with a mean annual temperature of 74. During the summer months the average temperature is 100, but the thermometer frequently shows a temperature of from 110 to 115, the heat though somewhat trying is much less oppressive than that of Sydney, even when it may be 10 or 15 higher, because of the lower relative humidity. The winter is, as a rule mild, with an average temperature of 53, but the temperature has been known to fall to 35 F. The annual rainfall is about 21 inches and received during the winter months between May and O6lober. PERTH. Latitude 32 S., in Western Australia, enjoys a mean annual temperature of 65, with a climate which, owing to the large tracts of sandy soil, is peculiarly dry and healthy; the rainfall received principally in the winter months, June, July, August and September amounts to about 33 inches. 284 BRISBANE. Latitude 27 28' S., the capital of Queensland, has a climate which is more uniformly hot than that of the other Australian colonies ; it is agreeable in the winter months, but though very hot during the summer the heat is less oppressive than in some of the other parts of Australia. The temperature ranges between 106 and 35 and the mean annual temperature is 69. The rainfall occurs chiefly during the summer months, December, January and February, at which season the air is hot and steamy. In 1893 an excep- tionally heavy rainfall occurred during the first week of February, when over 77 inches fell in four days in the Blackall ranges near Brisbane ; it was owing to the floods which occurred in consequence of this excessive rainfall that H.M.S. Paluma, a gunboat employed in the surveying service, was stranded in the Botanic Gardens at Brisbane. NEW ZEALAND. The climate is on the whole temperate, but shows considerable diversity in the various parts of the country. That of Auckland may be described as sub-tropical ; Wellington is, from its situation in respecl: to Cook's Straits, (w : hich divides the North and South Islands), peculiarly liable to boisterous stormy weather. Dunedin, in the South Island, has a climate very similar to that of England, and is very suitable for those who have become run down in health by too long residence in a warm climate, or who have suffered from a malarial fever. TASMANIA. HOBART. Approximate Latitude 43S., situ- ated on the Derwent river, enjoys a peculiarly genial climate. English fruits grow here in a manner quite unknown in England, and in the case of apples attain a much larger size than at home. The mean annual temperature is is 54'5 F. The mean summer temperature is 62, and mean. winter temperature 49, and a rainfall of about 20 inches which is well distributed over the year; on an average there are about 145 rainy days. BARBADOS. Latitude 13 7' 39" N., has a mean annual temperature of about 76, with an extreme range of tempera- ture between 91 or 92 and 57 F. The rainfall averages nearly 53 inches and the mean annual relative humidity is about 67 per cent. BERMUDA. Latitude 32 17' 40" N., enjoys an equable and temperate climate with a temperature of 70, the range being as a rule between 85 and 50. During the winter mpnths (November to April) it is visited by many people from Canada and the United States in order to escape the rigours of the continent during that season. In 1897 the maximum temperature for the year was 87 '9 and the minimum 50, and 28 5 the mean relative humidity was 79 varying between 70 and 84. The average annual rainfall is about 60 inches evenly dis- tributed throughout the year. BRITISH GUIANA. Capital, GEORGETOWN, has a warm climate with a limited range of temperature (between 89 and 70), with a mean of about 80. The hottest period is from September to November. The prevailing winds are from the N.E. and blow during most of the year mitigating considerably the heat. The rainy seasons are between June and August and December and February, with a total rainfall of about 82 inches. Yellow fever at one time prevalent is now only met with occa- sionally, but there is a good deal of malarial fever on the coast. CANADA. ESQUIMALT. Situated in Vancouver Island, Approximate Latitude 48 25' N., enjoys a marine climate with the absence of extremes met with in the interior of Canada. The lowest temperature recorded in two years is, according to Dr. P. H. Bryce,* 8F.,the lowest monthly average 20 F., and the highest temperature in summer 82 F. The air is drier than on the coast in England and the rainfall is less, and is received chiefly during the winter. The comparatively small amount of rainfall received at Esquimalt is due to its sheltered posi- tion, the moisture-bearing winds having been already partly drained by condensation which occurred on striking the high coast-line. NOVA SCOTIA. HALIFAX. Approximate Latitude 44-5 N. The temperature ranges between 88and i ibelow zero with a mean annual temperature of 65 F. The average rainfall per annum is 34 inches. The winters which are warmer than those of places in the interior are nevertheless cold and damp, owing to the cold Labrador current, but the climate in the summers, commencing in June, and the autumns, up to Novem- ber, leaves nothing to be desired. QUEBEC. MONTREAL and QUEBEC both possess climates which are healthy and bracing. The mean annual temperature of Montreal, Latitude 45*32 N. is 42-4* \\ith a range of from 91 to 12 below zero. On gth January, 1859 the phenomenal temperature of 43 F., was recorded. The annual rainfall amounts to about 27 inches. CAPE COLONY. The mean annual temperature at Cape Town (approximate Latitude 34 S.) is 64'5 F. ; the mean summer temperature is 71*5 F., whilst that of spring and autumn is 64-5 F., and the winter mean temperature is 57'2 F. f In 1891 the absolute maximum temperature was 96'! F., which occurred in January, and the absolute minimum tem- perature was 36-6 F., occurring in July. The prevailing The Climates and Health Resorts of Canada. By Dr. P. H. Bryce. t Official Handbook of the Cape and South Africa. 286 wind from November to March is that known as the " South- Easter " or'' Cape Doctor," this being a moisture-laden wind from the sea, loses its moisture when forced to ascend Table Mountain, and in so doing forms the apparently permanent cloud known as the " Table Cloth " ; at other times the wind is frequently from the N.W. The average rainfall in the Cape peninsula, taken for 50 years, is 25*46 inches falling on from 45 to 80 days. The mean relative humidity in the hot month of January, 1891, was 69 and that in the cold month of July, 67. The mean annual relative humidity is 67. The climate is equable with a clear dry atmosphere, very suitable to those suffering from anaemia, or convalescing from diseases con- tracted in warm or malarial places, or in facl convalescing from any severe illness. CEYLON. The mean annual temperature at Colombo is about 81 F', the temperature varies little throughout the year. The coolest months are December and January, the hottest April and May. The climate is warm but fairly" healthy. The rainy seasons are from April to June and September to November; the average annual rainfall is 100 inches. FALKLAND ISLANDS. The climate is healthy, the winter temperature ranges between 30 and 50 and that of the summer between 40 and 65. Fiji. Capital, SUVA. The climate is warm but healthy, the temperature ranges from 94 to 60. The average tem- perature in the cool season is 72 and in the hot season 84 GIBRALTAR. Latitude 36 6' 20" N., has a mean annual temperature of 64-5; in 1897 the temperature ranged between 36*8 and 94, with a mean annual minimum of 57*4 F., and a mean annual maximum of 71*6 F. The mean relative humidity varies between 62 per cent, in June and 81 per cent, in November. The mean annual rainfall is 34-5 inches; in 1897 it was 27*63 inches. The climate is hot during the summer months but invigorating and agreeable during the winter and spring up till May. The most trying feature of the summer is an easterly wind, known as the Levante, which is ex- ceedingly hot, damp, and depressing, whilst the wind from the west, known as the Poniente, is cool and refreshing and is not confined to any particular season. HONG KoNG. Latitude 22 16 $2" N.. shows a range of temperature usually between 96 F. and 42 F., but 99 F. has been recorded in September, and 32 F. in February; the mean annual temperature is about 74*5 F. ; the relative humidity varies between 70 per cent in November, and 86 per cent in January and February, the mean annual relative humidity is about 78 per cent. The average annual rainfall 287 is 90*17 inches, which falls chiefly between May and Septem- ber during the S.VV. monsoon; in 1897 over 112 inches of rain fell; in 1860 there was a minimum rainfall of 5972 inches, and the highest record is i2O'66 inches. The climate is very hot and exhausting when the S.W. monsoon is blowing, the temperature varying between 80 and 99", with a difference of 10 between day and night. When the N.E. monsoon prevails from November to January, the weather is cool and healthy and often bracing; the most trying feature during the winter months is the liability to sudden changes in tempera- ture, at one part of the day the heat may be almost tropical, whilst at another period it will be cold, with a cutting North wind. JAMAICA. Situated between 17 43' and 18 32' N. Latitude. Tbe mean annual temperature at Kingston is 82 F., and varies between 87'8 and 707. The annual rainfall averages 34 inches, and falls chiefly between October and February. The land and sea breeze is peculiarly well marked in Jamaica. LEEWARD ISLANDS. Comprising Antigua with Barbuda and Redonda (small island dependencies), St. Christopher and Nevis with Anguilla or Little Snake Island (a depen- dency), Dominica, Montserrat and the Virgin Islands are all situated between 15 and 19 N. Latitude, enjoy a warm climate, which is for the most part dry ; the mean annual temperature is about 80. The hottest weather is experienced between May and October, and the rainy season is from June to November. The island of Dominica has the greatest rainfall in the group, with an average rainfall of 120 inches. The climate in the lowlands is very humid, owing to the large amount of vegetation. In August, Sep- tember and October the Trade Wind becomes weak, and it is during this period that hurricanes occasionally occur. MALTA. Latitude 35 53' 49" N. has a mean yearly temperature of from 53 to 66'2 K, with a mean maximum of about 70 and mean minimum of 62' i. The summer months from the middle of June to the early part of September are hot, the temperature ranging between 71 and 87 F. In 1897 the maximum temperature was 94'6 F. on i4th September, and the minimum was 47^2 F. on 3ist January. In winter the temperature varies as a rule between 48 and 58, but occasionally rises above or falls below these limits. The average rainfall in 1897 amounted to 13*26 inches, in 1899 it was 17-8 inches; the mean annual relative humidity is about 72. The prevailing winds in summer are easterly, with occasional Sciroccos (S.E. winds) which are hot damp winds 288 exceedingly oppressive and relaxing. Violent gales from the N.E. are met with from time to time between November and April, they are known locally as Gregales. NATAL. The mean annual temperature at Durban is 70 F. ; the climate on the coast of Natal is (except during the winter months) tropical and ennervating. The highest temperature at Durban according to Dr. C. Lawrence Herman,* was 99 F. in 1875, and the lowest 45 F., with a mean daily range of I7'O5- The approximate mean daily temperatures were highest, 82 F., lowest, 56 F., and the total rainfall was 54*78 inches falling on 131 days. The rainy season is from October to March inclusive, and the prevailing winds are alternately from N.E. to E. and from S.W. to S. NEWFOUNDLAND. The climate is healthy and bracing; the temperature rarely falls below o F. in winter, and ranges in summer between 70 and 8o c F. Off the banks ot Newfoundland fogs are apt to occur at all seasons for reasons already given on page 247, but they are especially common in June and July. When the fogs occur with easterly winds they extend to a much greater height than those which take place during calms. SIERRA LEONE. Latitude 8 29' 30" N., possesses a climate which is warm and damp, and is therefore ennervating ; malarial fevers are most prevalent at the commencement and termination of the rainy season (May to October). Temper- ature varies as a rule between 89 and 62; in 1897 tne absolute maximum was 93*6 on igth January, and the mean maximum was 84*2 F., in the same year the minimum temperature was 66'8 F. on igth October, and the mean minimum was 74' i F., with a mean of 79' 1 F. The mean annual relative humidity is about 72, it varies between 64 and 86, August being the month when it is highest. The rainfall in 1897 was 164-3 inches. Between December and February (inclusive) a very dry easterly w r ind laden with fine sand off the desert, called the Harmattan, occasionally blows and may last a day or two or even a fortnight at a time, its dire6tion at Sierra Leone is from E.S.E. SINGAPORE. Latitude i" 16' N., situated almost on the equator, shows no clearly defined seasons ; rain falls through- out the year with 167 as the average number of rainy days and 91*8 inches of rainfall, but the rainfall has, during one year, amounted to as much as 123 inches falling on 209 days, and also reached a minimum total of 58*4 inches falling on 119 days. In 1898 the maximum shade temperature was 89'4 F. "Official Handbook of the Cape and South Africa. 289 in May, and the minimum temperature was 73-1 F. in January, or a total range of 16*3 F. The mean range is 12-7 viz., from 86'8" F. to 74-1 F. In 1898 the greatest range in any month was in March, when the temperature ranged between 88' i F. and 73-3 F., i.e., through 14-8 F., May coming next with a difference of 14-2 F. between the highest and lowest temperatures, whilst in December the range was least, viz., 10*7 F. The extremes in 17 years are 94 F and 63 F. Relative humidity averages 81 per cent., saturation being 100. Although Eygpt is not a British possession its climate is so remarkable as to demand a short notice. The climate is a singularly healthy one, and by reason of its dryness is peculiarly suitable as regards Cairo and Upper Egypt for convalescents from acute illness and also for cases of early tuberculosis, and anaemia, whilst those suffering from rheumatic affections benefit much by residence in Egypt on account of the dryness of the air. The mean annual temperature at Cairo in 1890 was 7i'5i F., and during the years 1887-90 it was 74 F. The highest mean monthly temperatures were in the year 1890 85-75 F. and 85-55 F. in July and August respectively, whilst the mean temperature during December, January and February were respectively 60-60 F., 53-64 F., and 59*05 F. On the coldest days in Cairo tne thermometer never sinks below 34 F., whilst on the hottest days it may occasionally amount to 112 F. Snow is recorded to have fallen at Cairo in 1855, but this was very exceptional. The mean annual temperature at Alexandria is 68-9 F., at Port Said, 71-0 F., at Ismailia, 72-0 F., and at Suez, 72*6 F. 2QO INDEX TO PART I. PAGES 65-68. INDEX TO PART II. PAGES 207-212. INDEX TO PART III. Air, Determining weight of .. .. .. 237 Physical characters of .. .. 213 ,, Weight of .. .. .. 213,237 Aitken's experiments on Dust . . . . 244 Altitude, Influence of, on Climate . . 275, 276 Measurement of .. .. .. 218 Anemometer, Dine's. . .. .. .. 259 ,, Lind's .. .. .. 259 ,, Robinson's .. .. .. 260 Aneroid Barometer .. .. .. 217 Anticyclones . . . . . . 266, 269 Apjohn's Formula . . . . . . 237 Aqueous Vapour . . . . . . . . 232 Aqueous Vapour, action of, as a screen . . 241 Artillery Fire and Cloud dispersion . . . . 254 Atmidometers . . . . . . . . 241 Atmospheric Electricity .. .. 271,273 Atmospheric Pressure, Variations in . . . . 266 Aurora, Australis and Borealis. . .. .. 272 Barometers .. .. .. .. 213 Barometers, Corrections for .. .. 214,217 Barometer, " Fortin's " ... .. .. 214 Barometer, Kew Marine . . . . . . 216 Beaufort Notation . . . . . . . . 262 Blizzards, Nature of . . . . . . 252 Boyle's Law .. .. .. .. 213 Buys Ballot's Law . . . . . . 258 Capacity Correction .. .. .. .. 217 Charles' Law .. .. .. .. 213 Cirrus Clouds . . . . . . . . 249 Climate . . .. .. .. 274, 279 Cloud-line, Height of . . . . . . 247 Clouds .. .. .. .. 247 Cold Climates . . . . . . . . 274 Cold Currents .. .. .. .. 277 Cold, Effects of exposure to .. .. .. 231 Cold, Sensation of . . . . . . 222 "Cold Wall" .. .. .. ..246 Compass, Mariner's . . . . . . 263 Configuration of Land, Effect on Climate of . . 276 Continental type of Climate . . . . 274 Cumulus Clouds . . . . . . . . 248 Cyclones . . . . . . . . 267, 269 Daniell's Hygrometer .. .. .. 234 Dalton's Law .. .. .. .. 239 Density of Air, Circumstances affecting . . . . 247 Density of Air, how determined . . . . 237 Dew and Dewpoint . . . . . . . . 243 Diminished Air Pressure, Effects of .. .. 220 Dine's Hygrometer . . . . . . . . 233 Dine's Portable Pressure Anemometer . . 259 Direction of Wind ^ .. .. .. .. 262 Dust, Action of . . . . . . 244 291 Effects of Heat and Cold . . . . 230, 231 Evaporation . . . . . . . . 235', 239 Latent Heat of .. .. .. 240 Evaporimeters, Richard's, Piches', Wild's .. 241 Factors (Glaisher's), Table of .. .. .. 281 Fohns . . . . . . . . 265 E s . , W 244,245 tortins Barometer .. .. .. 214 Free Surfaces, Effed of . . . . . . 244 Gay Lussac's Pipette . . . . . . 216 Glaisher's Tables .. .. .. ..280,282 Glazed Frost . . . . . . . . 244 Gradient, Barometric . . . . 256, 257 Hail.. .. .. .. .. 253 Hail-stones, Measurement of . . . . 255 Heat .. .. .. .. 222 Heat, Specific . . . . . . . . 222 Heat and Cold, Effects of . . . . . . 230, 231 Heat Waves . . . . . . . . 243 Humidity, Absolute and Relative . . . . 233 Humidity, Sudden changes in, effect on Health .. 238 Hygrometers, Various .. .. .. 233,234 Hygroscope, Saussure's Hair . . . . . . 238 Hypsometer . . . . . . . . 224 Inclination, Clouds of .. .. .. 249 Increased Air Pressure, Effects on Health of . . 221 Index error .. .. .. .. 217 Interfret . . . . . . . . 248 Inversion Movement.. .. .. .. 247 Isobars . . . . . . . . 256, 257, 258 James' Col , Formula for wind pressure . . . . 258 . Ke\v Marine Barometer .. .. .. 216 Latent Heat of Vaporisation .. .. .. 240 Latitude . . . . . . . . 275 Lightning Conductor . . . . . . 273 Lightning, Nature of . . . . . . 272 Marine Climate . . . . . . . . 274 Mariner's Compass . . . . . . 263 Mason's Hygrometer. . .. .. .. 234 Mercury as a medium for Thermometers . . 223 Meridian . . . . . . . . . . 263 Mill, on the floating of Dust Particles . . 245 Monsoons . . . . . . . . 265 Mountain Air and Disease. . . . . . 220 Mountain Climates . . . . . . . . 274 Mountains, Effects of, on Climate . . . . 278 Negrettis' Thermometer . . . . . . 226 Newfoundland, Fogs off coast of . . 246 Nimbus Cloud . . . . . . . . 250 North, How to find the . . . . 263 Ocean Currents, Effect of on Climate . . . . 277 Paradoxical action of Snow . . . . 253 Piche evaporimeter . . . . . . . . 241 Pole's formula for water storage . . . . 240 Pressure, Effects of Atmospheric . . . . 220 ,, Plate Anemometer .. .. 259 Proximity of sea, Effect on Climate of . . 276, 277 2Q2 Rain . . . . . . . . 250 Rain-band in solar speftrum . . . . . . 242 Rainfall, Influence on Climate of . . . . 278 Rain Gauge .. .. .. .. 251 Rainwater, Storage of . . . . 240 "Rainy-day" .. .. .. .. 252 Rarefied Air, Efieft of, on health . . . . 220 Regnault's Hygrometer . . . . . . 234 Relative Humidity, Definition of . . . . 233 Return-shock . . . . . . . . 272 Richard's Evaporimeter .. .. .. 241 Rotation of Earth, Effect on wind direction of . . 258 Rutherford's Thermometer . . . . 226 St. Elmo's Fire .. .. .. .. 272 Saturation of Atmosphere . . . . . . 233 Saussure's Hair Hygrometer . . . . . . 238 Snow . . . . . . . . 252 Soil, Influence of, on Climate . . . . . . 279 Solid, Liquid, and Gaseous states . . . . 222 Sound, Rate at which, travels . . . . . . 271 Specific Heat . . . . . . . . 222 Spirit as a medium for Thermometers . . . . 223 Steam under various pressures . . . . 224 Stevenson's Screen . . . . . . . . 225 Strachan's Measurement of Altitude . . . . 218 Stratus Clouds . . . . . . . . 249 Syphon Barometer .. .. .. 217 Syphons, Limit as to use of . . . . . . 220 Sunshine Recorders . . . . . . 228 Table of Factors (Glaisher's) .. .. .. 281 Table of Vapour Tensions . . . . 282, 283 Telephone gongs ringing during thunderstorms . . 272 Temperature distinguished from heat . . . . 222 Tension, Definition of Vapour . . . . . . 233 Thermometers . . . . . . . . 224 ,, Mercurial minimum, Casella's .. 226 Negretti's .. .. .. 226 Phillip's .. .. .. 226 ,, Radiation . . . . 227, 228 Wet and Dry Bulb . . . . 235 Thunderstorms, audibility of . . . . 272 Time, Local . '. . . . . . . 263 Trade Winds . . . . . . . . 264 Unit of Heat . . . . . . . . 222 Vapour, Definition of . . . . . . 235 Vapours, in relation to other gases . . . . 232 Vapour Tension, Tables of . . . . . . 280 Vegetation, Influence of on Climate . . . . 279 Vernier . . . . . . . . 215 Warm Climates . . . . . . 274 Wave-clonds . . . . . . . . 249 Wet and Dry Bulb Thermometers . . . . 234 Wind .. .. .. .. ..256 Wind, Effect of, on Health . . . . 265, 278 Winds, Prevailing, Effeds of, on Climate . . . . 278 Winds, Trade . . . . . . . . 264 Charpentier & Co., Printers, Portsmouth. OF THE UNIVERSITY RETURN MARIAN KOSHLAND BIOSCIENCE AND TO > NATURAL RESOURCES LIBRARY 2101 Valley Life Sciences Bldg. 642-2531 LOAN PERIOD JNE MONTH LOAK ALL BOOKS MAY BE RECALLED AFTER 7 DAYS. DUE AS STAMPED BELOW. DUE NOV 2 9 2002 SUBJECT TO REG ALL FORM NO. DD 8 UNIVERSITY OF CALIFORNIA, BERKELEY 12M 5-01 Berkeley, California 94720-6500 YC 18076