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MANUAL 
 
 OF 
 
 SCIENCE FOR TEACHERS 
 
 CONTAINING 
 
 ANSWERS TO THE PRACTICAL QUESTIONS 
 
 AND PROBLEMS IN THE AUTHOR'S 
 
 SCIENTIFIC TEXT-BOOKS 
 
 BY 
 
 j. DORM: AN STEE^E, PH.D., K. o. s. 
 
 AUTHOR OF THE FOURTEEN-WEEKS SERIES IN NATURAL SCIENCE ^^^ 
 
 paftc 
 
 Bi < 
 
 REVISED EDITION 
 
 TO ACCOMPANY THE POPULAR PHYSICS, POPULAR CHEMISTRY, 
 PHYSIOLOGY, AND NEW DESCRIPTIVE ASTRONOMY 
 
 O S 
 
 o S 
 o 
 
 NEW YORK : CINCINNATI : CHICAGO > r ~* 
 
 ^ CJQ 
 
 AM:KRICAN BOOK: COMPANY 
 
A POPULAR SERIES 
 
 IN 
 
 NATURAL SCIENCE, 
 
 BY 
 
 J. DQR.MAN STEELE, F*n.D., K.O.S., 
 
 A uihor of the Fourteen Weeks Series in Natural Science, etc., etc. 
 
 New Popular Chemistry. New Descriptive Astronomy. 
 
 New Popular Physics. New Hygienic Physiology. 
 
 New Popular Zoology. Popular Geology. 
 
 An Introduction to Botany. 
 
 The Publishers can supply (to Teachers only) a Manual containing Answers 
 to the Questions and Problems in Steele's entire Series. 
 
 BARNES' HISTORICAL SERIES, 
 
 ON THE PLAN OK 
 
 STEELE'S FOURTEEN-WEEKS IN THE SCIENCES. 
 
 A Brief History of the United States. 
 A Brief History of France. 
 
 A Brief History of Ancient Peoples. 
 
 A Brief History of Mediaeval and Modern Peoples. 
 A Brief General History. 
 
 A Brief History of Greece. 
 
 A Brief History of Rome. 
 
 A Popular History of the United States. 
 
 Copyright, 1888, by A. S. BARNES & Co. 
 J?<tuitiTr*w 
 
 Add'l 
 
PREFACE. 
 
 SINCE the publication of the former edition of this Manual, 
 Steele's Physics and Chemistry have been thoroughly revised, 
 and the Hygienic Physiology has been published. The present 
 issue has been prepared to accompany these later editions, and 
 includes complete reference to all the problems and practical 
 questions contained in Steele's Popular Physics, Popular Chemis- 
 try, Hygienic Physiology, and New Descriptive Astronomy. 
 Great pains have been taken to revise and compare the prob- 
 lems, which are fully, and, it is thought, accurately solved. 
 The practical questions, as in the former edition of the Manual, 
 are often not answered in full, yet sufficiently so to furnish a 
 key to the more perfect reply. The use of the text-books is 
 presupposed, and the statements merely supplement, or apply 
 the theories therein contained and explained. Upon many points 
 there may be, and often is, a difference of opinion. On these 
 mooted questions only that view which appeared to the author 
 to have preponderance of argument has been advanced, leaving 
 the subject open for the discussion of other theories. 
 
 The former edition of the Manual can still be obtained by 
 those teachers who continue to use the earlier editions of the 
 Sciences, although, with a few exceptions, the problems and 
 questions therein answered are incorporated with those which 
 have been added in the present issue. 
 
 DECEMBER, 1888. 
 
 163 
 
ANSWERS ;; 
 
 TO THE 
 
 PKACTICAL QUESTIONS AND PROBLEMS 
 
 IN THE 
 
 POPULAR PHYSICS. 
 
 36 ! A rifle-ball thrown against a board standing 
 on its end will knock it down ; the same bullet fired at the 
 board will pass through it without disturbing its position. 
 Why is this? 
 
 The ball which is thrown has time to impart its motion to 
 the board; the one fired has not. 
 
 2. Why can a boy skate safely over a piece of thin ice, 
 when 9 if he should pause, it would break under him di- 
 rectly ? 
 
 In the latter case there is time for the weight of his body 
 to be communicated to the ice; in the former, there is not. 
 
 3. WJiy can a cannon-ball be fired through a door 
 standing ajar, without moving it on its hinges ? 
 
 Because the cannon-ball is moving so quickly that its mo- 
 tion is not imparted perceptibly to the door. 
 
 4. Wliy can ^ve drive on the head of a hammer by sim- 
 ply striking the end of the handle ? 
 
 This can only be done by a quick, sharp blow, which will 
 drive the wooden handle through the socket before the motion 
 has time to overcome the inertia of the iron head. A slow, 
 steady blow will be imparted to the head, and so fail of the 
 desired effect. 
 
2 AJVSWJSBS TO PRACTICAL QUESTIONS 
 
 5. Suppose you were on a train of cars moving at, the 
 rate of SO miles per hour ; ivith ^vhat force ^vould you be 
 thrown forward if the train vvere stopped instantly ? 
 
 With the same velocity which the train had, or 44 feet per 
 second. Your momentum would be your mass multiplied by 
 this velocity. 
 
 0. In what line does a stone fall from the mast-head of 
 a vessel in motion ? 
 
 In a slightly curved line, produced by the two forces grav- 
 ity and the forward motion of the vessel. 
 
 7. If a ball be dropped from a high tower it ivill strike 
 the earth a little east of a vertical line. Why is this ? 
 
 In the daily revolution of the earth on its axis, from west 
 to east, the top of the tower moves faster than the bottom, be- 
 cause it passes through a larger circle. "When, therefore, the 
 ball falls, it retains that swifter easterly motion, and so strikes 
 very slightly east of the vertical. 
 
 8. It is stated that a suit was once brought by the driver 
 of a light wagon against the owner of a coach for damages 
 caused by a collision. The complaint was that the latter 
 was driving so fast, that when the two carriages struck the 
 driver of the former was throivn forward over the dash- 
 board. Show how his own testimony proved him to have 
 been at fault. 
 
 When the light wagon was suddenly stopped, its driver went 
 on with the same speed at which the wagon was moving. That 
 this threw him forward over the dash-board, proves his speed 
 to have been unusual. 
 
 9. Suppose a train moving at the rate of 3O miles per 
 hour ; on the rear platform is a spring-gun aimed parallel 
 'with the track, and in a direction precisely opposite' to the 
 motion of the car. Let a ball be discharged with the exact 
 speed of the train, where would it fall ? 
 
 In a vertical line to the track. The two equal, opposite mo- 
 tions would exactly destroy each other. 
 
IN POPULAR PHYSICS. 3 
 
 10. Suppose a steamer in rapid motion and on its deck 
 a tnan Jumping. Can he jump farther by leaping the 
 way the boat is moving or in the opposite direction? 
 
 It will make no difference as long as he jumps on the deck. 
 Should he jump off the boat, then the effect would be different. 
 
 11. Could a party play ball on the deck, of an ocean 
 steam- ship when moving along at the rate of 2O miles 
 per hour, without making allowance for the motion of 
 the ship ? 
 
 They could. The ball would have the motion of the ship, 
 and would move with it in whatever direction they might 
 throw it. 
 
 37 12. Since "action is equal to reaction," why is it not 
 r,o dangerous to receive the "kick" of a gun as the force 
 of the bullet ? 
 
 The kinetic energy varies as the square of the velocity ; and 
 the velocity with which the gun moves backward is as much 
 less than that with which the bullet moves forward, as the gun 
 is heavier than the bullet. For this reason a heavy gun will 
 kick much less than a light one. 
 
 13. If you were to jump from a carriage in rapid 
 motion, would you leap directly totvard the sx>ot on which 
 you wished to alight? 
 
 No ; because as one jumps from the carriage he has its for- 
 ward motion, and will go just as far ahead, while leaping, as 
 he would if he had remained in the carriage. He should, there- 
 fore, aim a little back of the desired alighting-place. 
 
 14. If you wished to shoot a bird in swift flight, would 
 you aim directly at it? 
 
 No. The bird will fly forward while the bullet is going to 
 it. One should, therefore, aim a little in advance. 
 
 15. At ^vl^at parts of the earth is the centrifugal force 
 the least? 
 
 The poles. The distance from axis to surface is there re- 
 duced to zero. 
 
4 ANSWERS TO PRACTICAL QUESTIONS 
 
 16. What causes the mud to fly from the ivheels of a 
 carriage in rapid motion ? 
 
 The centrifugal force (the momentum of the mud). 
 
 1 7. Wtiat proof have ^ve that the earth was once a soft 
 tn ass ? 
 
 It is flattened at the poles. This effect is produced upon a 
 ball of soft clay by simply revolving it on a wire axis. 
 
 18. On a curve in a railroad , ivhy is one track always 
 higher than the other ? 
 
 The outer track is raised in order that centrifugal force and 
 gravity, acting together, may combine to keep the average 
 pressure perpendicular to the track. 
 
 19. What is the principle of the sling ? 
 
 The sling is whirled until a strong centrifugal force is gen- 
 erated ; the string, the centripetal force, is then released, when 
 the stone flies off at a tangent. 
 
 20. The mouth of the Mississippi Miver is about 2\ miles 
 farther from the center of the earth than its source. What 
 causes its water to thus " run up hill " ? 
 
 The centrifugal force produced by the rotation of the earth 
 on its axis tends to drive the water from the poles toward the 
 equator. Were the earth to stand still in its daily rotation, the 
 Gulf of Mexico would empty its waters back through the Mis- 
 sissippi to the northern regions. 
 
 21. Is it action or reaction that breaJcs an egg ivheti 1 
 striJte it against the table ? 
 
 The reaction of the table. 
 
 22. Was the tnan philosophical who said " it tvas not 
 the falling so far but the stopping so quick that hurt 
 him"? 
 
 He was. 
 
 23. If one person rims against another, which receives 
 the greater bloiv ? 
 
 Action is equal to reaction ; hence the momentum given up 
 by the one is equal to that received by the other. 
 
IN POPULAR PHYSICS. 5 
 
 24. Would it vary the effect if the two persons were 
 running in opposite directions ? 
 
 The blow would then be the sum of both their momenta. 
 
 If they were running in the same direction ? 
 
 The blow would be equal to the difference of their momenta. 
 
 25. Why can you not fire a rifle-ball around a hill? 
 
 Because a single force always produces motion in a straight 
 line. 
 
 26. Wliy does a heavy gun "kick" less than a light 
 one ? 
 
 See problem 12. 
 
 27. A man on the deck of a large steamer draws a 
 stnall boat toward him. Can yott express the ratio of the 
 ship's motion to that of the boat ? 
 
 The ship moves as much less distance than the boat, as the 
 boat's mass is less than that of the ship. 
 
 28. Suppose a string, fastened with a nail at one end, 
 will just support a weight of 25 Ibs. at the other. Unfasten 
 it, and let tivo persons piill upon it in opposite directions. 
 How much can each pull ivithout breaking it ? 
 
 25 Ibs. The second person, in the latter case, can pull as 
 much as the nail did in the former. The tension in the string 
 is 25 Ibs., and the action of the one person is just balanced by 
 the reaction of the other. 
 
 29. Can a man standing on a plat form- scale make 
 himself lighter by lifting up on himself? 
 
 He can not ; because action and reaction are equal and op- 
 posite. 
 
 30. Why can not a man lift himself by pulling up 
 on his boot-straps ? 
 
 See last problem. 
 
 31. With ivhat momentum would a steam-boat weigh' 
 ing 1,OOO tons, and moving with a velocity of 1O feet per 
 second, strike against a sunken rock ? 
 
6 ANSWERS TO PRACTICAL QUESTIONS 
 
 1,000 tons = 2,000,000 Ibs. 2,000,000 x 10 = 20,000,000 units 
 of momentum. 
 
 32. With what momentum would a train of cars weigh- 
 ing 1OO tons, and running 1O miles per hour, strike against 
 an obstacle ? 
 
 The velocity per second is 14f feet. 100 tons = 200,000 Ibs. 
 The momentum is 200,000 x 14f = 2,933, 333^ units of momen- 
 tum. 
 
 33. Wliat would be the comparative kinetic energy of' 
 two hammers, one driven with a velocity of 2Q feet per 
 second, and the other 1O feet ? 
 
 20 2 = 400. 10 2 = 100. 400 : 100 : : 4 : 1. 
 
 Hence the kinetic energy of the first, or its ability to ac- 
 complish work, will be four times that of the second. This 
 principle is of great importance in all cases where percussion is 
 concerned. The highest velocity attainable is to be sought. 
 
 34. If a 1OO horse-poiver engine can propel a steamer 
 5 miles per hour, ivill one of 20O Jiorse-poivcr double its 
 speed ? 
 
 By no means. Resistance is proportional to / y 2 . (See Popu- 
 lar Physics, p. 65.) To double the velocity would require over 
 400 horse-power. 
 
 3<>. Why are ships becalmed at sea sometimes floated 
 toy strong currents into dangerous localities without the 
 Knowledge of the crew ? 
 
 As there are no fixed objects with which to compare their 
 motion, the officers are not sensible of any movement, and so 
 are drifted far out of their course. 
 
 3856*. A man in a ^vagon holds a 50-lb. weight in his 
 hand. Suddenly the wagon falls over a precipice. Will 
 he, while dropping, bear the strain of the ^veight ? 
 
 No. While on solid ground, his hand resisted the tendency 
 of the weight to fall toward the earth's center of gravity ; but 
 all are now descending freely under the influence of gravity, 
 and he no longer feels the pressure. 
 
IN POPULAR PHYSICS. 7 
 
 37. Wliy are we not sensible of the rapid motion of the 
 earth ? 
 
 Because all the objects around us are moving in the same 
 direction with the earth, and there is nothing at hand with 
 which to compare. 
 
 38. A feather is dropped from a balloon which is im- 
 mersed in and swept along by a swift current of air. Will 
 the feather be blown away, or will it appear to a person in 
 the balloon to drop directly doivu ? 
 
 It will seem to drop directly downward, as if in a dead 
 calm. Its fall is vertical, however, only as regards the balloon, 
 and not as regards the earth. 
 
 (See Stewart's Physics, p. 18.) 
 
 39. Suppose a bomb-shell, flying through the air at the 
 rate of 5OO feet per second, explodes into two parts of equal 
 weight, driving one half forward in the same direction as 
 before, but with double its former velocity. What would 
 become of the other half? 
 
 One half will go forward with a double velocity ( 1,000 feet 
 per sec.), and the other half will be checked and will fall directly 
 
 to the ground. 
 
 (See Stewart's Physics, p. 37.) 
 
 40. Wliich ivould have the greater penetrating power, 
 a small cannon-ball with a high velocity, or a large one 
 with a low velocity ? 
 
 The former would penetrate, while the latter would have 
 the greater momentum. . - 
 
 41. There is a story told of a man who erected a huge 
 pair of bellows in the stern of his pleasiire-boat 9 that lie 
 miglit always have a fair ^vind. On trial, the plan failed. 
 In which direction should he have turned the belloivs ? 
 
 In the manner adopted at first, of turning the nozzle toward 
 the sails, the action of the wind against the sails and the reac- 
 tion of the bellows against the boat just balanced each other. 
 If the man had turned the nozzle backward, he could have saved 
 the reaction of the bellows to move the boat. This would, how- 
 ever, have been a costly and bungling mode of navigation. 
 
8 ANSWERS TO PRACTICAL, QUESTIONS 
 
 42. If a man and a boy were riding in a wagon, and, 
 on coming to the foot of a hill, the man should take up the 
 boy in his arms, ^vould that help the horse ? 
 
 No change would be produced in the weight of the entire 
 establishment drawn by the horse, as no readjustment of the 
 load would modify the attraction of gravity which produces the 
 weight. Also, action reaction ; so the man would press down 
 on the wagon an amount equal to the weight of the boy. 
 
 4:3. If we ivliirl a pail of tvater swiftly around on its 
 oivn axis, ivhy will the water tend to leave the center of 
 the pail ? 
 
 The centrifugal force is compounded with the force of grav- 
 ity, and at each point of the surface the water level is at right 
 angles to their resultant. The centrifugal force increases with 
 distance from the axis, hence the water surface becomes con- 
 cave. 
 
 44. IVJiy will the foam collect at the holloiv in the cen- 
 ter? 
 
 The foam, being lighter than the water, has less momen- 
 tum, in proportion to its volume, and is forced back by the 
 heavier particles. 
 
 45. If tivo cannon-balls, one weighing 8 Ibs. and the 
 other 2 Ibs., be /ired ^vith the same velocity, which will go 
 the farther ? 
 
 The former has much less surface in proportion to its weight. 
 It will therefore go much farther against the resistance of the 
 air. 
 
 46. Resolve the force of the wind tvhich turns a com- 
 mon ivindmill, and show hoiv one part acts to push the 
 tvJieel against its support, and one to turn it around. 
 
 This case is exactly like that of the action of the wind 
 against the sail of a ship, as shown in the text on p. 29. 
 
 47. When an animal is jumping or falling, can any 
 exertion made in mid-air change the motion of its center 
 of gravity ? 
 
AV POPULAR PHYSICS. 9 
 
 The center of gravity falls steadily 16.08 feet, whatever 
 other force may act on the body. 
 
 (See Second Law of Motion.) 
 
 48. If one is riding rapidly, in which direction will he 
 be thrown when the horse is suddenly stopped ? 
 
 In the same direction in which he is going. He has the 
 motion of the carriage, and his momentum carries him for- 
 ward. 
 
 49. When standing in a boat, why, as it starts, are we 
 thrown backivard ? 
 
 Because our bodies tend to remain stationary, while the 
 boat carries our feet forward. 
 
 50. When carrying a cup of tea, if we move or stop 
 quickly, why is the liquid liable to spill ? 
 
 The momentum of the tea tends to keep it still or in mo- 
 tion, as the case may be. If we move the cup quickly, the 
 motion is not imparted to the liquid soon enough to overcome 
 this momentum. "When, therefore, we start, the tea spills out 
 backward ; or, when we stop, it spills out forward. We under- 
 stand this if we can tell why a cup of tea is more liable to 
 spill than one of sugar. 
 
 51. Why, when closely pursued, can we escape by dodg- 
 ing? 
 
 "We turn sharply. Our pursuer, ignorant of our design, can 
 not overcome his momentum so as to turn as quickly, and 
 hence is carried past. 
 
 52. WJiy is a carriage or sleigh, 'when sharply turning 
 a corner, liable to tip over ? 
 
 Because its, momentum tends to carry it directly forward. 
 
 53. Wiiy, if you place a card on your finger, and on top 
 of it a cent, can you snap the card from under the cent 
 without knocking tJie latter off your finger ? 
 
 Because the friction between the card and the cent is so 
 slight that, by a quick snap, you can give motion to the former 
 without affecting the latter enough to make it fall off. 
 
10 AJSWJBRS TO PRACTICAL QUESTIONS 
 
 54. Why is a " running jump " longer than a " stand- 
 ing jump " ? 
 
 This is an example under the first law of motion. The mo- 
 mentum of the person when running (mxv) is added to the 
 force with which he finally springs from the ground for the 
 jump. 
 
 55. Why, after the sails of a vessel are furled, does it 
 still continue to move ? and why, after the sails are spread, 
 does it require some tiine to get it under full headway? 
 
 This illustrates the tendency of matter to continue in its 
 present state, whether of rest or of moticn. For the former 
 part of the question, apply the first law of motion, and for the 
 latter, the second paragraph on p. 21 cf the Physics. If, on 
 starting with a heavy load, the horses leap suddenly forward, 
 they will break the harness ; but, by a steady, constantly-in- 
 creased draught, they will communicate motion to the mass. 
 
 56. Why can a tallow candle be fired through a board? 
 
 Because of its high velocity. Motion can not be communi- 
 cated at once to the entire mass of the board, hence this yields 
 at the place where pressure is suddenly applied. 
 
 COHESION. 
 
 48 ! Why can we not weld apiece of copper to one of 
 iron ? 
 
 Cohesion acts most readily between molecules of the same 
 kind. 
 
 2. Why is a bar of iron stronger than one of wood ? 
 
 All we can say is that there is more cohesion between its 
 molecules. The wood, moreover, is perforated with minute hol- 
 low tubes, so that its molecules can not be so compactly massed 
 together as those of the iron. 
 
 3. Why may a piece of iron, when perfectly ivelded, be 
 stronger than before it was broken ? 
 
 By the hammering, more particles are brought within the 
 range of cohesion. 
 
IN POPULAR PHYSICS. 11 
 
 4. Why do drops of different liquids vary in size ? 
 
 Because they vary in cohesive force. 
 
 5. Why, when you drop medicine, will the last few 
 drops contained in the bottle be of a larger size than the 
 others ? 
 
 The pressure of the liquid in the bottle is less, and there- 
 fore they form more slowly. 
 
 6. Why are drops larger if you drop them sloivly? 
 
 There is more time for the adhesive force of the bottle to 
 act on the liquid, and so a larger drop can be gathered. 
 
 7. Why, if you melt scraps of zinc, will they form a 
 solid mass w/ien cooled ? 
 
 The heat overcomes, in part, the attraction of cohesion, so 
 that the particles flow freely on each other. They now all 
 come within the range of cohesion, so that when the metal 
 cools they are held by that force in a solid mass. 
 
 8. In what liquids is the force of cohesion greatest? 
 
 Mercury, molasses, etc. 
 
 9. Name some solids that will volatilize tvithout melt- 
 iny. 
 
 Arsenic, camphor. 
 
 10. Why can glass be ivelded ? 
 
 Because, like iron, it becomes viscous before melting. 
 
 11. Name some substances that can not be ivelded. Why 
 not? 
 
 Wood can not be welded, nor can lead or bismuth. They 
 can not be made to assume the viscous condition. 
 
 12. What liquids would you select for showing surface 
 tension ? 
 
 Solution of soap in water is the most convenient. The dif- 
 ference in tension between films of different kinds of liquid is 
 well shown by carefully dropping oil of coriander or oil of cin- 
 namon, or minute fragments of clean camphor on the surface 
 of perfectly clean water. 
 
12 ANSWERS TO PRACTICAL QUESTIONS 
 
 ADHESION. 
 
 54 1. Why does cloth shrink when wet ? 
 
 By adhesion the water is drawn into the pores of the cloth. 
 The fibers are thus expanded sidewise and shortened length- 
 wise. The cloth "fulls up" or thickens while it shortens and 
 narrows (shrinks) in the process. 
 
 2. Why do sailors at a boat-race wet the sails ? 
 
 The pores being full and expanded make the sails more 
 compact. They will, therefore, hold the wind better. 
 
 3. WJiy does not writing-paper blot ? 
 
 Because the pores are filled with sizing. (See Popular Chem- 
 istry, p. 216.) 
 
 4. IVJiy does paint tend to prevent wood from shrink- 
 ing? 
 
 Because it fills the pores of the wood at its surface. 
 
 5. What is the shape of the surface of a glass of water 
 and one of mercury? 
 
 Ordinarily the former is concave and the latter convex. 
 
 6. Why can ^ve not dry a toivel perfectly by wringing ? 
 
 Because of the strength of the force of adhesion, by which 
 the water is held in the pores of the cloth. 
 
 7. Why will not water run through a fine sieve when 
 the wires have been greased ? 
 
 Because of reversed capillarity between oil and water. 
 
 8. Why will camphor dissolve easily in alcohol and not 
 in water ? 
 
 Because there is a strong adhesion between the- alcohol and 
 camphor, and but little between the water and camphor. 
 
 ,9. Why tvill mercury rise in zinc tubes as ivater does in 
 glass tubes ? 
 
 Because of the strong adhesion between zinc and mercury. 
 
IN POPULAR PHYSICS. 13 
 
 10. Why will ink spilled on the edge of a booh extend 
 farther inside than if spilled on the side of the leaves? 
 
 Because the sensible pores of the paper are short, being only 
 the thickness of a leaf, while the spaces between the leaves are 
 longer and continuous. 
 
 11. If you should happen to spill some ink on the edge 
 of your book, ought you to press the leaves together ? 
 
 Yes ; to make it as nearly solid as possible, until blotting pa- 
 per can be applied to remove what has not soaked into the book. 
 
 12. Wliy can yon not mix oil and water ? 
 
 Because there is little adhesion between them. 
 
 13. IVliy ^vill water wet your hand while mercury will 
 not? 
 
 Because in the former case there is strong adhesion, in the 
 latter but little. 
 
 14. Why is a tub or pail liable to fall to pieces if not 
 filled tvith water or kept in the cellar ? 
 
 Because the moisture dries out of the pores, and the wood 
 shrinks so as to let the hoops fall off. 
 
 15. Name instances where the attraction of adhesion is 
 stronger than that of cohesion. 
 
 "Wood fastened by glue will often split before the glue will 
 yield. Paper stuck with paste, and bricks with mortar, are also 
 examples. 
 
 16. Wliy does the ivater in Fig. 18 stand higher inside 
 of the tube than next the glass on the outside ? 
 
 There is the influence of a larger surface of glass in pro- 
 portion to the quantity of water to be lifted. 
 
 17. Why will clothes-lines tighten and sometimes break 
 during a shower ? 
 
 The rope absorbs water, and expands transversely. This 
 
 shortens it with so much force as often to break it. The 
 
 shrinking of new cloth when wet illustrates the same prin- 
 ciple. 
 
14 ANSWERS TO PRACTICAL QUESTIONS 
 
 IS. In casting large cannon, the gun is cooled by a 
 stream of cold water. Why ? 
 
 The object of this is to cause the iron to cool more quickly, 
 and so not give the molecules time to arrange themselves in 
 crystals. 
 
 19. Why does paint adhere to wood? Chalk to the 
 blackboard ? 
 
 These are illustrations of the force of adhesion. 
 
 20. Wliy does a toivel dry one's face after washing ? 
 
 The sensible pores of the cloth absorb the water from the 
 face by adhesion. 
 
 21. Why will a greased needle float on water ? 
 
 The grease prevents the needle from being wetted, and the 
 toughness of the surface film cf water is sufficient to with- 
 stand the weight of the needle. 
 
 22. IVhy is the point of a pen slit ? 
 
 So that we may widen at will the surface of contact be- 
 tween the ink and the paper. The ink is prevented from de- 
 scending rapidly, when the slit is not open, by the grip of its 
 surface film. 
 
 23. Why is a thin layer of glue stronger than a thick 
 one ? 
 
 The adhesion between the glue and the wood is stronger 
 than the cohesion between the particles of glue ; hence the 
 thinner the layer of glue the fewer the particles acted upon 
 only by the latter or weaker force. 
 
 GRAVITATION. 
 
 73 ! JVlien an apple falls to the ground, hoiv much 
 does the earth rise to meet it ? 
 
 The earth falls as much less distance than the apple, as its 
 mass is greater. 
 
IN POPULAR PHYSICS. 15 
 
 2. Will a body weigh more in a valley than on a mount- 
 
 It will, because the distance to the earth's center is less, 
 
 .7. Will a pound weight fall more slowly than a two- 
 pound weight ? 
 
 They will both fall in the same time, except the slight dif- ^ 
 ference which is caused by the resistance of the air. Galileo (^ 
 propounded this view, and proved it, in the presence of 
 nesses, by letting unequal weights fall from the leaning tower 
 of Pisa. 
 
 4. How deep is a well 9 if it takes three seconds for a stone 
 to fall to the bottom of it ? 
 
 S-igt 2 
 
 S = 16 x 3- = 144 feet. 
 
 5. Is the center of gravity always ivithin a body as, 
 for example, a pair of tongs ? 
 
 No. It may be entirely outside, and is usually so for a pair 
 of tongs. 
 
 6. In a ball of equal density throughout, ivhere is the 
 center of gravity ? 
 
 At the center of the ball. 
 
 7. Why does a ball roll down hill ? 
 
 Because the line of direction falls without the small base of 
 the ball. 
 
 S. Why is it easier to roll a round body than a square 
 one? 
 
 Because the base of the ball is so much smaller, and there- 
 fore the center of gravity need not be raised to bring the line 
 of direction without. 
 
 9. Why is it easier to tip over a load of hay than one of 
 stone ? 
 
 Because the center of gravity in a load of hay is very high, 
 and in a load of stone very low. Therefore the center of grav- 
 
16 ANSWERS TO PRACTICAL QUESTIONS 
 
 ity in the former need not be raised much to bring the line of 
 direction without the base, while in the latter it must be. 
 
 1 0. Why is a pyramid the stablest of structures ? 
 
 Because the base is so broad and the center of gravity so 
 low. The center of gravity must therefore be lifted very high 
 before the line of direction will fall without the base. 
 
 11. When a hammer is thrown, on which end does it 
 most often strike ? 
 
 The heavier end. 
 
 12. Why does a rope-ivalker carry a heavy balancing- 
 pole? 
 
 Because in this way he can easily shift his center of 
 gravity. 
 
 13. Wliat would become of a ball if dropped into a hole 
 bored through the center of the earth ? 
 
 If we assume the earth to be at rest, the ball will move 
 with diminishing acceleration, but increasing speed, to the cen- 
 ter. The momentum thus acquired would carry it an equal 
 distance beyond, if there be no resistances, and the acceleration 
 being now negative, the ball will be brought momentarily to 
 rest at the surface on the opposite side. It will then fall back 
 past the center, and continue thus oscillating forever. If we 
 assume the earth to be rotating, the ball will sink from fast- 
 moving toward slow-moving parts, and strike against the side 
 of the hole. Friction will soon bring it to rest at the earth's 
 center. 
 
 1. Would a clock lose or gain time if carried to the top 
 of a mountain ? 
 
 i It would lose time, because the force of gravity would be 
 lessened. At the North Pole it would gain time, because there 
 the force of gravity would be increased. 
 
 15. In the winter, would you raise or lower the pendu- 
 lum-bob of your clock? 
 
IiV POPULAR PHYSICS. 17 
 
 I would lower it, since the cold of winter shortens the pen- 
 dulum, and this movement of the bob would counteract that 
 change. 
 
 16. IVliy is the pendulum-bob generally made flat ? 
 
 To decrease the friction of the air. 
 
 It '. IVJiat beats off the time in a ivatch ? 
 
 The vibration of the balance-wheel. 
 
 IS. Is solved in the book. 
 
 19. What should be the length of a pendulum at New 
 York to vibrate half-seconds ? 
 
 (1 sec.) 2 : (~|- sec.) 2 :: 39.1 in. : x 9. 7 + inches. 
 
 To vibrate quarter-seconds ? 
 
 (1 sec.) 2 : ( sec.) 2 :: 39.1 in. : x = 2. 4 + inches. 
 To vibrate hours ? 
 
 (1 sec.) 2 : (3600 sec.) 2 : : 39.1 in. : x = 7997.7 miles.* 
 
 20. What is the proportionate time of vibration of two 
 pendulums, 16 and 64 inches long, respectively ? 
 
 According to the 2d law of pendulums, 
 Time of vib. of 1st : Time of vib. of 2d : : /16 : *Qi : : 4 : 8 : : 1 : 2. 
 
 21. Why, when you are standing erect against a ivall, 
 and a piece of money is placed between your feet, can you 
 not stoop fonvard and pick it up ? 
 
 By leaning forward you bring the center of gravity in front 
 of your feet, and, as on account of the wall, you can not 
 throw any part of your body back to preserve the balance, you 
 fall forward. 
 
 22. If a toiver ivere 198 feet high, with tvhat velocity 
 ivould a stone, dropped from the summit, strike the 
 ground ? 
 
 & = 2gh (See p. 64, foot-note.) 
 v* = 64x198 
 v = 112.5 feet. 
 
 * Nearly the diameter of the earth. 
 
18 ANSWERS TO PRACTICAL QUESTIONS 
 
 23. A body falls in 5 seconds: with what velocity does 
 it strike the ground ? 
 
 v = 32t. v = 32x5. v = 160 feet. 
 
 74 24. Hoiv far ivill a body fall in 1O seconds? 
 
 s = 16 2 . s = 16 x 10 2 = 1600 feet. 
 With what velocity ivill it strike the ground ? 
 
 v = 32t. v = 32 x 10 = 320 feet. 
 
 25. A body is thrown upward with a velocity of 11)2 
 feet the first second ; to what lieight will it rise ? 
 
 Equation (1), v = 32t. 192 = 32t. t = Q sec. 
 (2), s = 16 2 . s = 16 x 6 2 = 576 feet. 
 
 26. A ball is shot upward with a velocity of 250 feet ; 
 to what height ivill it rise? How long ivill it continue to 
 ascend ? 
 
 Using equations (1) and (2), as in the last problem, we have 
 
 t = 8 sec. 
 s = 1024 feet. 
 
 28. Are any two plumb-lines parallel ? 
 
 They are not, since they point to the earth's center of grav- 
 ity. No two spokes of a wheel can be parallel. 
 
 29. A stone let fall from a bridge strikes the water in 
 three seconds. What is the lieight ? 
 
 s = 16 2 . s - 16 x 3 2 = 144 feet. 
 
 30. A stone falls from a church steeple in 4: seconds. 
 Wfiat is the height ? 
 
 s = 16P. s = 16 x 4 2 = 256 feet. 
 
 31. How far would a body fall the first second at a 
 height of 12,OOO miles above the earth's surface? 
 
 (16,000 mi.) 2 : (4000 mi.) 2 : : 16 feet :x = l foot. 
 
 32. A body at the surface of the earth weighs WO tons; 
 what would be its weight 1,OOO miles above ? 
 
 (5000 mi.) 2 : (4000 mi.) 2 : : 100 tons : x - 64 tons. 
 
I2V POPULAR PHYSICS. 19 
 
 33. A boy ivishing to find the height of a steeple lets flu 
 tin arrow that just reaches the top, and then falls to the 
 ground. Tt is in the air 6 seconds. Required the height. 
 
 s = 16t*. s = 16 x 3 2 = 144 feet. 
 
 34. An object let fall from a balloon reaches the 
 ground in 1O seconds. Required the distance. 
 
 s = 16 x 10 8 = 1600 ft. 
 
 35. In what time will a pendulum 4O feet long make a 
 vibration ? 
 
 According to the 2d law of pendulums, and taking the 
 length of a seconds pendulum as 39 in., we have: 
 
 1 sec. : x : : y^39 =^40 x 12 in. 
 
 '480 
 39 
 x = 3. 5 + sec. 
 
 36. Two bodies in space are 12 miles apart. They 
 weigh 1OO and 2OO Ibs. respectively. If they should 
 fall together by force of their mutual attraction, what 
 portion of the distance would be passed over by each 
 body ? 
 
 The distance passed over by the two bodies is inversely as 
 their mass ; hence one moves 8 miles and the other 4 miles. 
 
 37. If a body weighs 2,OOO Ibs. upon the surface of 
 the earth, what would it weigh 2,OOO miles above ? 
 
 (6000 mi.) 2 : (4000 mi.) 2 : : 2000 Ibs. : x = 888f Ibs. 
 Hoiv much 5OO miles above ? 
 
 (4500 mi.) 2 : (4000 mi.) 2 : : 2000 Ibs. : x = 1580 + Ibs. 
 
 38. At what distance above the surface of the earth will 
 a body fall, the first second, 21\ inches? 
 
 A body falls 16 feet* (192 inches) at the surface of the 
 earth. 21^ inches are \ of 192 inches. Now, as the attraction 
 is inversely as the square of the distance, the distance must be 
 
 * According to the best authorities the distance is more nearly 16^$ feet. 
 
20 ANSWERS TO PRACTICAL QUESTIONS 
 
 /y/9, or 3 times that at the surface. Hence, the body must be 
 12,000 miles from the center, or 8,000 miles from the surface 
 of the earth. The problem may be solved directly by propor- 
 tion, thus : 
 
 x* : 4000 2 : : 192 inches : 21| inches. 
 
 x = 12000 miles (distance from the center). 
 
 12000 miles 4000 miles = 8000 miles. 
 
 89. How far will a body fall in 8 seconds ? 1,O24 feet. 
 In the 8th second? 24O feet. In 1O seconds? 1,6OO 
 feet. In the 3Oth second ? 944 feet. 
 
 4O. Hoiv long would it take for a pendulum one mile in 
 length to make a vibration ? 
 
 According to the" 1 second law of pendulums (Physics, p. 69), 
 
 1 sec. : x : :^S9 : A /5280x 12 in. 
 x = 40 + sec. 
 
 41. Wliat would be the time of vibration of a pendulum 
 04 meters long ? 
 
 (1 sec.) 2 : y? : : 1 meter (nearly) : 64 meters. 
 x = 8 seconds (nearly). 
 
 42. A ball is dropped from a height of 64 feet. At the 
 same moment a second ball is thrown upward with suffi- 
 cient velocity to reach the same point. Where will the two 
 balls pass each other ? 
 
 At the end of one second. The first ball would fall 64 feet 
 in 2 seconds ; the second would rise for 2 seconds, and they 
 would pass in 1 second, 48 feet above the ground. 
 
 43. Explain the following fact : A straight stick loaded 
 with lead at one end can be more easily balanced vertically 
 on the finger when the loaded end is upivard than when 
 it is doivnward. 
 
 When the loaded end is upward a slighter motion is needed 
 to bring the line of direction within the base. The principle is 
 similar to that of the balancing-pole of the gymnast. 
 
IN POPULAR PHYSICS. 21 
 
 44. If a body weighing 1 Ib. on the earth were carried 
 to the sun, it would weigh 27 Ibs. How much would it at- 
 tract the sun ? Ans. 27 Ibs. 
 
 75 45. Why does watery vapor float and rain fall ? 
 
 Perfect vapor, which is quite invisible, is lighter than air, 
 and is diffused through it. When condensed into minute drop- 
 lets forming clouds, these are prevented from falling fast be- 
 cause of the great amount of surface, in proportion to their 
 weight, exposed to the resistance of the air. 
 
 46. If a body weighs 1O Jcilos. on the surface of the 
 earth, ^v1lat ivill it ^veigh 1,OOO km. above ? 
 
 x : 10 kilos. : : (6,366 *) 2 : (7.36G) 2 
 x = 7.5 kilograms. 
 
 47. A body is thrown vertically upward with a velocity 
 of 1OO meters. Hoiv long before it ivill return to its origi- 
 nal position ? Ans. 2O.4 seconds. 
 
 48. How much time will be required for a body to fall 
 a distance of 2,OOO meters ? 
 
 Equation (6) s = $gl*. 2,000 = ?LpP. 
 .-. t = 20.2 seconds. 
 
 49. IVJiat would be the time of vibration of a pendulum 
 39.1 indies long at the surface of the moon, where the ac- 
 celeration of gravity is only 4.8 ft. ? 
 
 t : f : : -- : -4= (see 3d Law of Pendulum, p. 69). 
 
 Vo vV 
 
 t' = 2.58 seconds. 
 
 5O. What would be the time of vibration for the 
 same pendulum at the surface of the sun, where the accel- 
 
 * The radius, or semi-diameter of the earth, is given by French as- 
 tronomers at 6,366 km. 
 
22 ANSWERS TO PRACTICAL QUESTIONS 
 
 eration of gravity is 27 times what it is at the earth's sur- 
 face ? 
 
 t' = .19 + second. 
 
 51. How many vibrations per minute would be made 
 at the surface of the moon by a pendulum 4O ft. long ? 
 
 First find the time of a single vibration. 
 
 x 1 2 
 . / . . A/ ""'^ . A / " ' 
 
 mt ' V ~W ' V ~T8~~ 
 
 t = 9 + seconds. 
 
 Hence, in a minute, the number of vibrations will be not 
 quite 7. 
 
 52. A pendulum vibrates 2OO times in 15 minutes. 
 irJiat is its length? 
 
 15x60 
 
 = 4 seconds, the time of a single vibration. 
 
 x 791.8 inches, or 66 feet nearly. 
 
 53. For a certain clock in New York the pendulum was 
 made 5OO Ibs. in weight. JFJiat was the object in making 
 it so heavy ? 
 
 To secure regularity of motion by means of the large mass, 
 so that variations in resistance may be avoided as nearly as 
 possible. 
 
 54. Pendulums are often supported by knife-edges of 
 steel resting on plates of agate. Why ? 
 
 Because the friction between steel and agate is less than if 
 any other substances are used. It is desirable to avoid friction 
 as completely as possible. 
 
 55. The acceleration of gravity at the equator is 32.O88 
 ft. ; at the pole, 32.253ft. If a pendulum vibrates 3, GOO 
 times an hour at the equator, how many times an hour 
 will it vibrate at the pole ? 
 
IN POPULAR PHYSICS. 23 
 
 The number of vibrations per hour varies inversely as the 
 time of vibration of the pendulum. For t in the formula, 
 therefore, we may substitute the reciprocal of the number of 
 vibrations per hour. 
 
 1 . JL . . 1_ . 1_ 
 
 3600 ' x" ^3^088 ' V32T253 
 x = 3,609.36 times. 
 
 THE MECHANICAL POWERS. 
 
 94 1. Describe the rudder of a boat as a lever. 
 
 The water is the F, the boat the "W, and the hand the P. 
 As the W is between the F and the P, it is a lever of the 
 second class. By similar reasoning it is easy to analyze the 
 remaining cases, a door, a door-latch, etc. 
 
 952. Show the change that occurs from the second to 
 the third class of levers, when you take hold of a ladder at 
 one end and raise it against a building. 
 
 At first the ground is the F at one end, the hand the P 
 at the other, and the ladder the W hanging between ; hence this 
 is a lever of the second class. After a little, the F remaining 
 the same, the P is applied at one end, near the F, and the 
 ladder is the W hanging at the other ; hence this is now a 
 lever of the third class. 
 
 3. IVJiy is a pinch from the tongs near the hinge more 
 severe than one near the end ? 
 
 Because in the former case the tongs are a lever of the 
 first class in the latter, of the third. In the first class there 
 is a gain of power, in the third a loss. 
 
 4. Two persons are carrying a weight of 25 O lbs. 9 
 hanging between them from a pole 1O feet in length* 
 Wliere should it be suspended so that one ivill lift only 5O 
 Ibs. ? 
 
 One lifts 50 Ibs. ; the other 200 Ibs. The proportionate 
 length of the arms of the lever should be the same as the 
 proportionate weights i.e., 1 to 4. 10-5-5 = 2, the unit of 
 
24 AXSWEJRS TO PRACTICAL QUESTIONS 
 
 measure. Hence one arm is 2 feet long and the other 8 feet 
 long. PROOF. 50 x 8 = 200 x 2. This is the substance also of 
 the equation P x Pd = W x Wd. 
 
 5. In a lever of the first class, 6 feet long, where should 
 the F be placed so that a P of 1 Ib. will balance a W of 23 
 Ibs.? 
 
 6 feet = 72 inches. 72 *- 24 = 3, the unit of distance. The 
 W must be placed 3 in. and the P 69 in. from the F. PROOF. 
 23 x 3 = 1 x 69 (Prob. 4). 
 
 6. What P would be required to lift a barrel of pork 
 with a windlass whose ajcle is one foot in diameter and 
 handles ft. long? 
 
 P : W : rad. of axle : : rad. of wheel. 
 
 a: : 200 Ibs. : : J ft. : 3 ft. 
 
 x = 33 Ibs. 
 
 7. What sized axle, with a wheel 6 feet in diameter, 
 would be required to balance a W of 1 ton by a P of JLOO 
 Ibs.? 
 
 P : W : : diameter of axle : diameter of wheel. 
 
 100 Ibs. : 2,000 Ibs. : : x : 6 ft. 
 
 x = T % ft. = the diameter. 
 
 8. What number of movable pulleys would be required 
 to lift a W of 200 Ibs. with a P of 25 Ibs. ? 
 
 W = P x twice the number of movable pulleys ; 
 
 W 
 hence -p- = twice the number of movable pulleys. 
 
 200 -4-25 = 8. 8 -*- 2 = 4 = the number required. 
 
 9. How many Ibs. could be lifted with a system of 4 
 movable pulleys, and one fixed pulley to change the direc- 
 tion of the force, by a P of 1OO Ibs. ? 
 
 W = P x twice the number of movable pulleys. 
 100 Ibs. x (4 x 2) = 800 Ibs. = the W. 
 
IN POPULAR PHYSICS. 25 
 
 10. What weight could be lifted with a single horse 
 power (3 3 ,OOO Ibs. one foot high per minute) acting on a 
 system of pulleys shown in Fig. 62 ? 
 
 "W = 33,000 x2x2x2x2= 528,000 Ibs. 
 
 11. What distance should there be between the threads 
 of a screiv, that a P of 25 lbs. 9 acting on a handle 3 ft. 
 long, may lift 1 ton weight? 
 
 P : W : : Interval : Circumference. 
 
 25 Ibs. : 2,000 Ibs. : : x : 72 in. x 3.1416. 
 
 x = 2.83 -in. 
 
 12. How high could a P of 12 Ibs., moving 16 ft. along 
 an inclined plane, lift a W of 96 Ibs. ? 
 
 P : W : : height : length. 
 
 12 Ibs. : 96 Ibs. : : x : 16 ft. 
 
 X = 2 ft. 
 
 13. I wish to roll a barrel of flour into a wagon, the 
 booc of which is 4 ft. from the ground. I can lift but 24= 
 Ibs. How long a plank should I get ? 
 
 P : W : : height : length. 
 24 Ibs. : 196 Ibs. : : 4 ft. : x = 32f ft. 
 
 14. What Wean be lifted with a P of 1OO Ibs. acting 
 on a screw having threads 1 in. apart t and a handle 4 ft. 
 
 long? 
 
 P : "W : : Interval : Circumference. 
 
 100: x:: 1 : 4x12x3.1416 
 x = 15,079.68. 
 
 15. What is the object of the balls often cast on the ends 
 of the handle of the screw used in presses for copying let" 
 ters ? 
 
 By their momentum they make the motion more uniform 
 and continuous. 
 
 16. In a steelyard 2 ft. long, the distance from the 
 weight-hook to the fulcrum-hook is 2 in. How heavy a 
 body can be weighed with a 1 Ib. weight ? 
 
 24 in.- 2 in. = 22 in. 1 Ib. x 22 = 22 Ibs. = P. 
 22 Ibs. -*-2= 11 Ibs. =W. 
 
26 ANSWERS TO PRACTICAL QUESTIONS 
 
 17. Describe the change from the 1st to the 3d class of 
 levers, in the different ivays of using a spade. 
 
 When digging, the ground at the back of the spade is the 
 F ; the ground lifted is the W ; and the hand at the other end 
 is the P. As the "W" is at one end, P at the other, and the P 
 between, this is a lever of the 1st class. When throwing dirt, 
 the left hand at one end of the spade is the P ; the dirt at the 
 other end is the W, and the right hand between the two is the 
 P. As the P is between the P and the W, this is a lever of 
 the 3d class. 
 
 18. Wliy are not blacksmiths' tongs and fire tongs con- 
 structed on the same principle ? 
 
 The former are of the 1st class, as power is required : the 
 latter of the 3d class, as rapidity only is necessary. 
 
 19. In a lever of the 3d class, what W will a P of 5O 
 Ibs. balance, if one arm is 12ft. and the other 3 ft. long? 
 
 50 Ibs. : x : : 12 ft. : 3 ft. 
 x = 12|- Ibs. 
 
 96 2O. In a lever of the 2d class, ivhat W will a P of 
 50 Ibs. balance, with a lever 12 feet long and W 3 feet 
 from the F? 
 
 50 Ibs. : x:: 3ft. : 12ft. 
 x = 200 Ibs. 
 
 21. In a lever of the 1st class, what W will a F of 5O 
 Ibs. balance, with a lever 12 ft. long and the F 3 ft. from 
 the W? 
 
 50 Ibs. : x : : 3 ft. : 9 ft. 
 x = 150 Ibs. 
 
 22. In a wheel and axle, the F = 4O Ibs., W = 36O Ibs., 
 diameter of aocle = # in. Required the circumference of 
 the wheel. 
 
 P : W : : diameter of axle : diam. of wheel. 
 
 40 Ibs. : 360 Ibs. : : 8 in. : x = 72 in. = 6 ft., the diameter of wheel. 
 6 ft. x 3.1416 = 18.85 ft., the circumference of the wheel. 
 
7JV POPULAR PHYSICS. 27 
 
 23. Suppose in a wheel and axle the P 2O Ibs., the W 
 24O Ibs., and the diameter of wheel = 4 ft. Required the 
 circumference of the axle. 
 
 20 Ibs. : 240 Ibs. : : x : 48 in. 
 x = 4 in. (diameter of axle). 
 4 in. x 3.1416 = 12.56 in. (circumference). 
 
 24. Hequired , in a tvheel and axle, the diameter of the 
 wheel, the diameter of the axle being 1O inches, P 1OO 
 Ibs. and W = 1 ton. 
 
 100 Ibs. : 2,000 Ibs. : : 10 in. : x = 200 in. = 16f ft. 
 
 25. Why is the rim of a fly -wheel made so Jieavy ? 
 
 The largest momentum possible is desired. The velocity of 
 a particle is proportional to its radius in rotation. Hence the 
 largest part of the mass of the wheel is fixed at the rim. 
 
 26. Describe the hammer, when used in drawing a 
 nail, as a bent lever, i.e., one in which the bar is not 
 straight. 
 
 If a lever is bent, or if, when it is straight, the bar is not 
 at right angles to the lines of action of the P and the W, it is 
 necessary to distinguish between the arms of a lever and the 
 arms of the P and the "W, regarded as forces which have mo- 
 ments around the F. In the latter sense, the arms are the per- 
 pendiculars, dropped from the F to the lines of action of the 
 P and the W. 
 
 27 Describe the four levers shown in Fig. 46, when 
 both the load of hay and the weight are considered, re- 
 spectively, as the W and the P. 
 
 This is so fully answered in the text that no further expla- 
 nation seems necessary. The pupil should be required to as- 
 sume values for the W and for each of the lever arms, and 
 compute the weight of the wagon and hay together. Call his 
 attention to the fact that half the weight of the wagon and 
 hay is transmitted at the point P, and the other half at P' ; 
 also that the vertical rod at the lift serves only as a connector, 
 and not as a lever. 
 
28 AXSWJEKS TO PRACTICAL 
 
 HYDROSTATICS. 
 
 I 1 9 ! Why can housekeepers test the strength of lye, 
 by trying ivhether or not an egg ivill float on it ? 
 
 The potash dissolved in the water to form lye increases the 
 density of the liquid. When enough has been dissolved to make 
 its specific gravity greater than that of the egg, the egg will 
 float. This becomes, therefore, a simple but rough means of 
 testing the amount of potash contained in the lye. 
 
 2. Hoiv much water will it take to make a gallon of 
 strong brine ? 
 
 A gallon. The salt does not increase the volume of the 
 liquid. 
 
 3. Why ought a fat man to swim more easily than a 
 lean one ? 
 
 Because muscles and bones are heavier than fat. The spe- 
 cific gravity of a fat man is, therefore, less than that of a lean 
 one. 
 
 0. If ^ve let bubbles of air pass up through a jar of 
 water 9 why will they become larger as they ascend ? 
 
 The pressure of the water is less as they near the top, and 
 so they expand. 
 
 7. IFJiat is the pressure on a canal lock-gate 14 feet 
 high and lOfeet wide, ^vhen the lock is full of water ? 
 
 14 x 10 x 7 x 1,000 oz. = 980,000 oz. = 61,250 Ibs. 
 
 8. Will a pail of ivater 'weigh any more with a live fish 
 in it than without ? 
 
 If the pail were full before the fish was put in, then it will 
 make no difference, since the fish will displace its own weight 
 of water, which will run over. If the pail is only partially 
 filled, then, though the fish is upheld by the buoyancy of the 
 water, since action is equal to reaction, it adds its own weight 
 to that of the water. 
 
IN POPULAR PHYSICS. 29 
 
 9. If the ivater filtering down through a rock should 
 colled in a crevice an inch square and 25O feet high, open- 
 ing at the bottom into a closed fissure having 2 O square 
 feet of surface, what would be the total pressure tending to 
 burst the rock? 
 
 Neglecting the diameter of the fissure, the pressure is the 
 same on every square inch of the twenty square feet of sur- 
 face. 
 
 j^ 250 x 1,000 oz.x 20x144 = 31 
 144 > 1 1^ 
 
 10. Why can stones in water be moved so much more 
 easily than on land? 
 
 Because the water buoys up nearly one half of their 
 weight. 
 
 11. IVliy is it so difficult to wade in the water where 
 there is any current ? 
 
 Because we have to move not only the weight of our own 
 bodies, but also the water. The kinetic energy of this is pro- 
 portional to the mass displaced, and to the square of its velocity. 
 
 1 2O 12. Wliy is a mill-dam or a canal embankment 
 made small at the top and large at the bottom ? 
 
 Because the pressure of the water increases with the depth. 
 
 13. In digging canals, ought the engineer to take into 
 consideration the curvature of the earth ? 
 
 There is no necessity to do so. A water level is in practice 
 assumed to be horizontal. In geodetic surveys, like that of the 
 coast line of a country, allowance has to be made for the cur- 
 vature of the earth. Station points twenty miles apart, or 
 more, are taken, between which the earth's curvature is readily 
 calculable and perceptible. 
 
 14. Why does the bubble of air in a spirit-level move 
 as the instrument is turned ? 
 
 Because the air is lighter than the alcohol, and rises con- 
 stantly to the highest point. For this reason, also, the tube is 
 curved so as to be convex at the center. 
 
30 ANSWERS TO PRACTICAL QUESTIONS 
 
 15. Can a swimmer tread on pieces of glass at the bot- 
 tom of the ivater with less danger than on land ? 
 
 Yes. But he would still find it unadvi sable to try the ex- 
 periment. 
 
 16. Will a vessel displace more water in a fresh river 
 than in the ocean ? 
 
 In the fresh river, because the specific gravity, and hence 
 the buoyancy, of fresh water is less. 
 
 17. Will iron sink in mercury ? 
 
 No. It will float, like a cork on water. 
 
 18. The water in the reservoir in Neiv York is about SO 
 feet above the fountain in the City Hall Park. What is 
 the pressure on a single inch of the pipe at the latter point ? 
 
 (1,000 oz. x 80) H- 144 = 34.7 Ibs. 
 
 19. Why does cream rise on milk ? 
 
 Because it is lighter than the milk. 
 
 20. Ttiere is a story told of a Chinese boy who accident- 
 ally dropped Jiis ball into a deep hole, where he could not 
 reach it. He filled the hole with water, but the ball ivould 
 not quite float. He finally bethought himself of a lucky 
 expedient, which was successful. Can you guess it ? 
 
 He put salt in the water. 
 
 21. Which has the greater buoyant force, oil or water ? 
 
 Water, because its density is greater. 
 
 22. What is the weight of 4= cu. ft. of cork ? 
 
 1,000 oz. = the weight of 1 cu. ft. of water. 
 .240 = the spec. grav. of cork. 
 
 240 oz. = the weight of 1 cu. ft. of cork. 
 4 
 
 960 oz. = the weight of 4 cu. ft, of cork, 
 = 60 Ibs. 
 
IN POPULAR PHYSICS. 31 
 
 23. How many oz. of iron will a cubic foot of cork float 
 in water ? 
 
 1,000 oz. = weight of a cubic foot of water. 
 .240 = spec. grav. of cork. 
 
 240 = weight of a cubic foot of cork. 
 1,000 oz. 240 oz. = 760 oz., the buoyant force of a cubic foot. 
 
 24. IVJiat is the specific gravity of a body whose weight 
 in air is 3O grs. and in water 2O grs. <? 
 
 30 grs. 20 grs. 10 grs. 
 
 30 grs. H- 10 grs. = 3. 
 The body is three times as heavy as water. 
 
 25. Which is heavier, a pail of fresh-water or one of 
 salt-water ? 
 
 A pail of salt-water is as much heavier than one of fresh- 
 water as the weight of the salt added to make the brine. 
 
 26. Tlie weights of a piece of syenite-rock in air and in 
 water were 3941.8 <jrs. and 26O7.5 grs. Find its spec, 
 grav. Ans. 2.954. 
 
 27 A specimen of green sapphire from Slam weighed 
 in air 21.45 grs. 9 and in water 16.33 grs. Required its 
 spec. grav. Ans. 4.189. 
 
 28. A specimen of granite weighs in air 534.8 grs., 
 and in water 334.6 grs. Wliat is the spec, grav.? Ans. 
 2.671. 
 
 29. What is the volume of a ton of iron ? 
 
 1,000 oz. = weight of 1 cu. ft. of water 
 7.8 spec. grav. of iron. 
 
 7,800 oz. = weight of a cu. ft. of iron. 
 32,000 oz. (a ton of iron) -*- 7,800 (weight of a cu. ft.) = 4/g- cu. ft. 
 
32 ANSWERS TO PRACTICAL QUESTIONS 
 
 A ton of gold ? 
 
 1,000 oz. = weight of a cu. ft. of water. 
 
 19.34 = spec. grav. of gold. 
 19,340 oz. * weight of a cu. ft. of gold. 
 32,000 oz.* -4- 19,340 oz. = 1.6, the no. of cu. ft. 
 
 A ton of copper ? 
 
 1,000 oz. x 8.9 = 8,900 oz. 
 32,000 oz. -f- 8,9QO oz. = 3.6 (nearly) the no. of cu. ft. 
 
 30. WJiat is the weight of a cube of gold 4 feet on each 
 side? 
 
 4 3 = 64, the no. of cu. ft. 
 
 19,340 oz.* (no of oz. in 1 cu. ft.) x 64 = 77,360 Ibs. 
 
 31. A cistern is 12 ft. Iong 9 G ft. wide, and 1O ft. deep. 
 When full of water, what is the pressure, on each side? 
 
 On one side, 12 x 10 x 5 x 1,000 oz. = 600,000 oz. = 37,500 Ibs. 
 On one end, 6 x 10 x 5 x 1,000 oz. = 300,000 oz. = 18,750 Ibs. 
 
 32. Why does a dead fish always float on its back ? 
 
 It has its swimming-bladder located just under the spine ; 
 and this is the lightest part of its body, and, of course, comes 
 to the top as soon as the fish dies. 
 
 34. A vessel holds 1O Ibs. of 'water ; how much mer- 
 cury would it contain ? 
 
 Mercury is 13.5 times heavier than water. Hence the vessel 
 would contain 10 Ibs. x 13.5 = 135 Ibs. of mercury. 
 
 35. A stone weighs 70 Ibs. in air and 5O in water. 
 What is its bulk ? 
 
 70 50 = 20. 20 x 16 oz. = 320 oz., the weight of water displaced. 
 320 oz. is ^ of a cu. ft. 
 
 * In these solutions the student should notice that avoirdupois 
 is used in weighing the gold. To be exact, 1,000 oz., the weight of a cu. 
 ft. of water, should be reduced to Troy weight, and the Ib. gold taken * 
 12 oz. Troy, when the answer would be about 1.36 cu. ft. 
 
IN POPULAR PHYSICS. 33 
 
 56*. A hollow ball of iron weighs 1O Ibs. : what must be 
 its volume to float in water ? 
 
 10 Ibs. = 160 oz. As a cubic ft. of water weighs 1,000 oz., 
 the ball must displace such a part of a cu. ft. of water as 160 
 oz. is of 1,000 oz., or .16 cu. ft. 
 
 37. Suppose that Hiero's crown was an alloy of silver 
 and gold, and weighed 22 oz. in air and 2O% oz. in water. 
 What was the proportion of each metal ? 
 
 "Multiply the specific gravity of each ingredient by the 
 difference between it and the specific gravity of the compound. 
 As the sum of the products is to the respective products, so is 
 the specific gravity of the body to the proportions of the in- 
 gredients. Then, as the specific gravity of the compound is to 
 the weight of the compound, so is each of the proportions to 
 the weight of its material." American Cyclopedia. 
 
 Second method : 
 
 Let A = mass of crown = 22 
 
 " B = sp. gr. " = 14.66 
 
 " x = mass of gold 
 
 " x' = sp. gr. " = 19.26 
 
 " y = mass of silver 
 
 " y 1 = sp. gr. " 10.5 
 
 then 
 
 and since 
 
 mass 
 volume = 
 
 specific gravity' 
 we have 
 
 A _x y f 
 
 B"-tfV 
 
 whence we find (approximately), 
 
 Gold = 13.95 
 Silver = 8.05 
 
 1 2 1 38. Wliy ^vill oil f which floats on water, sink in 
 alcohol ? 
 
 The specific gravity of absolute alcohol is only .79 ; hence 
 even the dilute alcohol of commerce is lighter than most speci- 
 mens of oil. 
 
34 ANSWERS TO PRACTICAL QUESTIONS 
 
 39. A specific-gravity bottle holds 1OO gms. of ^vater 
 and ISO gms. of sulphuric acid. Required the density of 
 the acid. Ans. 1.8. 
 
 40. Wliat is the density of a body which weighs 58 gins. 
 in air and 46 gms. in water ? Ans. 4f . 
 
 41. What is the density of a body which iveighs 63 
 guns, in air and 35 gms. in a liquid of a density of .85 ? 
 Ans. 1.9125. 
 
 HYDRODYNAMICS. 
 
 129 1. Two faucets, one 8 feet and the other 4 feet be- 
 low the surface of the water in a cistern, are kept open for 
 a minute. How many times as much water can be drawn 
 from the first as the second ? 
 
 Hence the first delivers rather more than 41$ more than 
 the second. 
 
 2. How much water will be discharged per second from 
 a short pipe having a diameter of 4 inches and a depth 
 of 48 feet below the surface of the ^vater? 
 
 The cross section of the pipe is 16 x .7854 = 12.57 sq. inches, 
 = .087 sq. feet. _ 
 
 v = ^/'2gh = -v/64 x 48 = 55.4 
 55. 4 x. 087 = 4.8 cu ft. 
 
 3. When we pour molasses from a jug, why is the 
 stream so much larger near the nozzle than at some dis- 
 tance from it ? 
 
 Because, according to the law of falling bodies, the farther 
 the molasses fajls the faster it falls. The stream, therefore, 
 becomes smaller as it moves more swiftly, until, at last, it 
 breaks up into drops. 
 
 4. Ought a faucet to extend into a barrel beyond the 
 staves ? 
 
IN POPULAR PHYSICS. 35 
 
 No ; this would cause more friction, and increase the resist- 
 ance to outflow produced by cross currents. 
 
 5. What ivould be the effect if both openings in one of 
 the arms of Barker's Mill were on the same side ? 
 
 It would cease revolving. The pressure in each direction 
 would then be equal, and the arms would balance. 
 
 PNEUMATICS. 
 
 1 45 1. Why must we make tivo openings in a barrel 
 of cider when we tap it ? 
 
 One to let out the cider, and one to admit the air. 
 
 2. What is the weight of 1O cubic feet of air ? 
 
 100 cu. in. weigh 31 grs. ; hence 10 cu. ft. will weigh 31 grs. 
 x 172.8 = .7652 Ibs. avoirdupois. 
 
 3. What is the pressure of the air on one square rod of 
 land ? 
 
 2721 x 144 x 15 Ibs. = 588,060 Ibs. 
 
 4. What is the pressure on a pair of Magdeburg hemi- 
 spheres 4 in. in diameter, when the air is entirely ex- 
 hausted ? 
 
 On each hemisphere the pressure is equal to the area of a 
 great circle, multiplied by the pressure on each unit of area. 
 Hence on each hemisphere the pressure is 
 
 .7854 x 4 2 x 15 Ibs. = 188.5 Ibs. nearly. 
 The sum of the two opposite pressures is thus not quite 277 Ibs. 
 
 5. Hoiv high a column of water can the air sustain 
 when the barometric column stands at 28 in. ? 
 
 28 in. x 13^ = 31 feet. 
 
 6. Tf we should add a pressure of two atmospheres, 
 what ivould be the volume of 1OO cu. in. of common air ? 
 
 The pressure is trebled, and, according to Mariotte's law, the 
 volume will be reduced in the same proportion ; hence it will 
 be 100 cu. in. H- 3 = 33*- cu. in. 
 
36 ANSWERS TO PRACTICAL QUESTIONS 
 
 1467. If 9 while the water is running through the 
 siphon, we quickly lift the long arm, what will be the effect 
 on the water in the siphon ? If we lift the entire siphon ? 
 
 The question assumes the siphon to be flexible. If the bot- 
 tom of the long arm be below that of the short arm, the water 
 flows through it toward the lower level. By lifting it the rate 
 of flow diminishes until its level is the same as that of tho 
 short arm. On lifting it still higher, the water contained in the 
 siphon flows back through the short arm, and the siphon is 
 thus emptied. If, however, the whole siphon is lifted, it is 
 emptied through the long arm. 
 
 8. WJien the mercury stands at 29\ in. in the barome- 
 ter, how high above the surface of the ivater can ive place 
 the lower pump-valve ? 
 
 In theory, 29^ in. x 13 = 398} in.; in practice, the distance 
 is much less than this. 
 
 9. Can we raise water to a higher level by means of a 
 siphon ? 
 
 There is no power in a siphon ; it is only a way of guiding 
 the flow of water to a lower level. 
 
 10. If the air in the chamber of a fire-engine be con- 
 densed to T V its former bulk, what will be the pressure due 
 to the expansive force of the air on every square inch of 
 the air-chamber ? Ans. 24O Ibs. 
 
 11. IVtiat causes the bubbles to rise to the surface when 
 we put a lump of loaf-sugar in hot tea ? 
 
 The bubbles of air contained in the pores of the sugar rise 
 because they are lighter than the water. 
 
 12. When will a balloon stop rising ? IVJiat weight can 
 it lift ? 
 
 It will stop rising when the weight of the balloon and its 
 contents is just equal to that of the same volume of rarefied 
 air which it displaces. It can lift a weight equal to the dif- 
 ference between the weight of the hydrogen or coal gas with 
 which it is filled and that of the air in which it is immersed, 
 minus the weight of the balloon itself. 
 
IN POPULAR PHYSICS. 37 
 
 14. When smoke ascends in a straight line, is it a proof 
 of the rarity or density of the air ? 
 
 Of its density, because it shows that the smoke is much 
 lighter than the air, and so rises immediately. 
 
 15. Explain the action of the common leather-sucker. 
 
 There is nearly a vacuum between the sucker and the slab, 
 which is buoyed up by the pressure of the air beneath. 
 
 16. Did you ever see a bottle really empty ? 
 
 No. No absolute vacuum has ever been produced in a bottle 
 or any other vessel by human agency, so far as is known. 
 
 18. How does the variation in the pressure of the air 
 affect those ^vho ascend lofty mountains ? Who descend in 
 diving bells? 
 
 The outward pressure at a great, elevation is partly removed, 
 and the inner pressure remaining the same, the blood is often 
 forced through the ears, nostrils, etc. When one descends into 
 a deep mine the conditions are reversed : the outer pressure be- 
 comes in excess of the inner ; severe pain is felt in the ear-drum, 
 and ringing noises in the head become almost intolerable. These, 
 however, disappear after a time, when the equilibrium between 
 the internal and external pressure is restored. It is said that 
 Humboldt ascended where the mercurial column fell to 14 inches, 
 and descended in a diving-bell where it rose to 45 inches thus 
 making a variation of 31 inches, or a difference of 31,000 Ibs. 
 pressure on the body. 
 
 19. Explain the theory of t( sucking cider " through a 
 straw. 
 
 By the action of the muscles of the chest the lungs are 
 made to expand. A partial vacuum in them is thus produced, 
 and the pressure of the air hence forces liquid through the 
 straw up into the mouth. By closing the glottis at the right 
 moment this is prevented from going through the windpipe, 
 and it is at once swallowed. 
 
 20. Would it make any difference in the action of the 
 siphon if the limbs were of unequal diameter ? 
 
38 AXSWEKS TO PRACTICAL QUESTIONS 
 
 The flow of water through the narrower part of the siphon 
 would be faster than through the wider part. 
 
 21. What would be the effect of malting a small hole in 
 the top of a diving-bell while in use ? 
 
 It would allow the compressed air to be pushed out by the 
 pressure of the water below. 
 
 22. The pressure of the atmosphere being 1.O3 kg. per 
 sq. cm. 9 what is the amount on 1O sq. meters ? 
 
 103,000 kg. 
 
 ACOUSTICS. 
 
 184 1. Why can not the rear of a long column of 
 soldiers keep time to the music ? 
 
 Because it takes time for the sound-wave to pass down the 
 column, and hence those in the rear do not hear the music as 
 soon as those in front. 
 
 2. Three minutes elapse between the flash and the re- 
 port of a thunderbolt : hoiv far distant is it ? 
 
 If the air is at the freezing point, the distance is 
 1,090 ft, x 60 x 3 = 196,200 ft. 
 
 5. Five seconds expire between the flash and report of 
 a gun: what is the distance? 
 
 1,090 ft. x 5 = 5,450 ft. 
 
 4. Suppose a speaking-tube should connect tivo villages 
 1O miles apart. How long would it take a sound to pass 
 that distance ? 
 
 52,800 ft +- 1,090 ft. = 48.4 (sec.) 
 
 This is of course a theoretical case. The initial energy 
 manifested as sound would be transformed into other modes of 
 energy, such as heat, before complete transmission through so 
 great a distance in a speaking-tube, unless the sound be more 
 intense than that of the human voice usually is. 
 
IN POPULAR PHYSICS. 39 
 
 5. The report of a pistol-shot was returned to the ear 
 from the face of a cliff in 4: seconds. Hoiv far was it ? 
 
 .1,090ft. x2 = 2, 180 ft. 
 
 6*. What is the cause of the difference in the voice of 
 man and wom,an ? 
 
 Probably the difference depends largely on the thickness 
 and length of the vocal chords. The difference between a bass 
 and a tenor, a contralto and a soprano, depends largely also on 
 quality, just as the sound of the flute and violin on the same 
 note is recognizably different. 
 
 7. What is the number of vibrations per second neces- 
 sary to produce the fifth tone of the scale of C s ? 
 
 C 3 = 256 vibrations. 
 256 x f = 384. 
 
 8. Wliat is the length of each sound-wave in that tone 
 ivhen the temperature is zero F. ? 
 
 1,090 ft. -32 ft. = 1,058 ft. 1,058 -f- 384 = 2 ft. 9 in. (the length 
 of each wave). 
 
 9. What is the number of vibrations in the fourth tone 
 above C 3 ? 
 
 C 2 = 128 vibrations. 
 128 xf =192. 
 
 lO.Ifa meteor were to explode at a height of 60 miles, 
 ivould it be possible for its sound to be heard at sea-level ? 
 
 No. At such a height the atmosphere would be more rare 
 than in the best vacuum over produced by human means. The 
 explosion would produce a sound far too faint to be audible. 
 
 11. A stone is let fall into a well, and in four seconds is 
 heard to strike the bottom ; hoiv deep is the ^vell ? 
 
 Disregarding the minute interval required for the transmis- 
 sion of the sound, 
 
 S = P = 16 x 4 2 = 256 feet. 
 
40 ANSWERS TO PRACTICAL QUESTIONS 
 
 12. What time would be required for a sound to travel 
 five miles in the still water of a lake ? 
 
 s 5x5,280 
 * = = -= 5-6 seconds. 
 
 13. Does sound travel faster at the foot or at the top of 
 a mountain? 
 
 The density and elasticity of the air vary in the same pro- 
 portion ; hence if the temperature were the same on top of a 
 mountain that it is at the foot, the velocity of sound would be 
 the same, but as it is always colder, the velocity is less. 
 
 14. IVJiy is an echo weaker than the original sound ? 
 
 Because the intensity of the sound-wave is weakened at each 
 reflection. In addition to this, the sound which is perceived as 
 an echo has traveled over a much greater distance than that 
 which comes directly from the sonorous body. 
 
 15. IVlvy is it so fatiguing to talk through a speaking - 
 trumpet ? 
 
 Because it is unusual, and unusual effort is necessary to se- 
 cure adaptation to unusual conditions. 
 
 16. WJiy will the report of a cannon fired in a valley be 
 heard on the top of a neighboring mountain better than 
 one fired on the top of a mountain will be heard in the 
 valley ? 
 
 A sound always has the intensity given it by the density of 
 the atmosphere where it originated, and not of that where it is 
 
 heard. 
 
 (See Tyndall's Lectures on Sound, p. 40.) 
 
 17. Why do our footsteps in unfurnished dwellings 
 sound so startlingly distinct ? 
 
 ' In furnished rooms, the chairs, carpets, pictures, etc., break 
 up the echoes. Then, also, our footsteps are louder on an un- 
 carpeted floor. 
 
 18. Why do the echoes of an empty church disappear 
 when the audience assemble ? 
 
IN POPULAR PHYSICS. 41 
 
 The audience break up the echoes which interfere with the 
 original sound. Wires strung across a lofty room often serve 
 the same purpose to a slight extent. 
 
 19. What is the object of the sounding -board of a 
 
 By its vibrations and those of the body of air which it in- 
 closes, it re-enforces the sound of the wires. 
 
 20. During some experiments, Tyndall found that a 
 certain sound would pass through twelve folds of a dry 
 silk handkerchief, but ivould be stopped by a single fold of 
 a wet one. Explain. 
 
 (See TyndalTs Lectures on Light, p. 325, for a series of experiments show- 
 ing the action of moisture on the propagation of sound-waves.) 
 
 21. What is the cause of the musical murmur often 
 heard near telegraph lines? 
 
 It is produced by the vibration of the wires. These are 
 thrown into motion by the wind and other causes. 
 
 22. Why will a variation in the quantity of ^vater in 
 a goblet, when caused to sound, make a difference in the 
 tone ? 
 
 It changes the area of the vibrating portion of the glass. 
 
 23. At what rate (in meters) will sound move through 
 air at sea-level, the temperature being 2O C. ? 
 
 Sound moves at the rate of 1,090 feet at C. The differ- 
 ence is nearly 2 feet for each degree C. 
 
 1,090 feet + 40 feet =1,130 feet. 
 
 OPTICS. 
 
 235 1. Why is a secondary bow fainter than the pri- 
 mary ? 
 
 The primary is produced by one reflection and two refrac- 
 tions ; the secondary, by two reflections and two refractions. 
 The additional reflection weakens the ray 
 
42 ANSWERS TO PRACTICAL QUESTIONS 
 
 Wliy are the colors reversed ? 
 
 We can understand this by looking at Fig. 164. In one 
 bow we cee that the rays enter the drops at the top, and are 
 refracted at the bottom to the eye ; in the other, that the rays 
 enter at the bottom, and are refracted at the top to the eye. 
 
 2. WJiy can we not see around a house or through a 
 bent tube ? 
 
 The rays of light move in straight lines. 
 
 3. What color would a painter" use if he wished to rep- 
 resent an opening into a dark cellar ? 
 
 Black. 
 
 4. Is black a color ? 
 
 Np ; it is the absence of light, and hence of color. 
 Is white ? 
 
 No. It is the result of mixing a multitude of tints, each of 
 which loses its individuality as color by union with the rest. 
 
 5. By holding an object nearer a light, ivill it increase 
 or diminish the size of the shadow ? 
 
 It will increase it, because more rays are intercepted. 
 
 7. Where should ^ve look for a rainboiv in the morn- 
 ing ? 
 
 In the west. 
 
 <V. Can two spectators see the same rainboiv ? 
 
 They can not, because no two persons can be at the right 
 angle to get the same color from a drop. 
 
 9. Wliy, tvhen the drops of ivater are falling through 
 the air 9 docs the bow appear stationary ? 
 
 Because amid the multitude of drops there are always some 
 in the right direction. 
 
 10. Why can a cat see in the night better than a human 
 being ? 
 
IN POPULAR PHYSICS. 43 
 
 Because the pupils of its eyes are larger, and so admit more 
 
 light. 
 
 11. Why can not an owl see distinctly in daylight ? 
 
 Its eyes are adapted to faint light. That of bright sunshine 
 is therefore too dazzling. 
 
 12. Why are we blinded tvhen we pass quickly from a 
 dark into a brilliantly lighted room ? 
 
 The pupils of our eyes admit too much light, but they soon 
 contract to the proper dimensions, and we can then see dis- 
 tinctly. When we pass out from a lighted room into a dark 
 room, the conditions are reversed. 
 
 13. If the light on a distant planet is only ^ that 
 which ive receive, how does its distance from the sun com- 
 pare ivith ours ? 
 
 As the intensity of light is inversely as the square of the 
 distance, the distance is ^,/100 = 10 times as great as ours. 
 
 14. If ivhen I sit 6 feet from a candle I receive a cer- 
 tain amount of light, hoiv much ivill I diminish it if I sit 
 back 6 feet farther ? 
 
 As my distance from the light is doubled, the brightness is 
 inversely as 2 2 , or only as great. 
 
 15. Why do drops of rain, in falling, appear like liquid 
 threads ? 
 
 The impression the drop makes on the retina remains until 
 the drop reaches the ground. 
 
 16. W7iy does a towel turn darker when wet ? 
 
 More of the light is transmitted, and less reflected. "We see 
 this illustrated in greasing a bit of paper. It becomes semi- 
 transparent because more light passes through it, but looks 
 darker itself because less light is reflected to the eye. 
 
 17. Does color exist in the object or in the mind of the 
 observer ? 
 
44 ANSWERS TO PRACTICAL QUESTIONS 
 
 The property of absorbing energy of special wave length, 
 and reflecting that of another wave length which we perceive 
 as color, is a physical property of the object. The perception 
 of this, as of sound, or of temperature, is finally a mental act. 
 
 18. IVTiy is lather opaque, while air and a solution of 
 soap are each transparent ? 
 
 By repeated reflections and refractions in passing through 
 the mass of lather, no ray can pass through in a straight line. 
 Transparency is hence destroyed. 
 
 19. Why does it ivhiten molasses candy to pull it ? 
 
 The viscous mass, by repeated pulling, becomes fibrous. The 
 fibers at the surface reflect light more regularly, and hence the 
 candy appears more nearly white. 
 
 20. Why does plastering become lighter in color as it 
 dries ? 
 
 Because, as the water evaporates, the mortar transmits less 
 light, and reflects more light to the eye. 
 
 21. Why does the photographer use a lamp ivith a 
 chimney of red glass in the " dark room " ? 
 
 Because this glass transmits only the longer waves of light, 
 while chemical effect is produced chiefly by the shorter waves. 
 
 22. Is the common division of colors into " cold " and 
 " warm " verified in philosophy ? 
 
 Yes ; red contains more heat than violet. 
 
 23. Why is the image on the camera, Fig. 177, in- 
 verted ? 
 
 The rays cross each other at the focus of the double convex 
 lens. 
 
 24. Wliy is the second image seen in the mirror 9 
 14O, brighter than the first? 
 
 The first is formed by reflection from the glass, and the 
 second from the mercury. As the latter is a better reflector, 
 the second image will be brighter. Each image after that will 
 be weakened by the repeated reflection. 
 
IN POPULAR PHYSICS. 45 
 
 27. Which will be seen at the greater distance , a yellow 
 or a gray body ? 
 
 The yellow, since it is brighter. 
 
 28. IVlien a star is near the horizon, does it seem higher 
 or lower than its true place ? 
 
 Higher. The light in passing into our atmosphere, is re- 
 fracted downward, and the star appears in the direction from 
 which the ray enters the observer's eye. 
 
 29. Why can we not see a rainbow at midday ? 
 
 Because the sun is not in the right position. To produce 
 the ordinary rainbow, it must be toward the eastern or western 
 horizon. 
 
 30. What conclusion do we draiv from the fact that 
 moonlight shows the same dark lines as sunlight ? 
 
 That its light has the same source as that of the sun, and 
 is, indeed, reflected sunlight. 
 
 31. IFliy does the bottom of a boat seen under clear 
 ivater appear flatter than it really is ? 
 
 Because, by refraction, the bottom of the boat is apparently 
 elevated above its true place. 
 
 32. Of what shape docs a round body appear in 
 ^vater ? 
 
 It appears to be flattened ; and hence a round body looks 
 like an oval one. 
 
 33. Why is rough glass translucent while smooth glass 
 is transparent ? 
 
 The minute irregularities scatter the rays of light, and do 
 not allow them to pass freely to the eye of the observer. 
 
 34. Why can a carpenter looking along the edge of a 
 board tell ivhether it is straight ? 
 
 If the edge is straight, the light will be reflected uniformly 
 to his eye from the whole length. Any uneven places will make 
 dark and light spots. 
 
46 ANSWERS TO PRACTICAL QUESTIONS 
 
 35. Why can ^ve not see out of the windoiv after ive 
 have lighted the lamp in the evening ? 
 
 The glass reflects the light of the lamp back to our eyes, 
 and they adapt themselves to the increased amount. 
 
 36. Why does a ground-glass globe soften the light ? 
 
 It scatters the rays. 
 
 37. Why can we not see through ground-glass 01* 
 painted windows ? 
 
 They transmit the light irregularly to the eye, and not uni- 
 formly, like a transparent body. 
 
 38. Why does the moon's surface appear flat? 
 
 Because it is so distant that the eye can not detect the dif- 
 ference between the distance of the center and the circumfer- 
 ence. 
 
 39. Why can ^ve see farther with a telescope than ivith 
 the naked eye ? 
 
 Because it furnishes us more light with which to see a dis- 
 tant object. 
 
 40. Why is not snow transparent, liJte ice ? 
 
 Because it is discontinuous, and the rays of light are broken 
 by multitudinous reflections and refractions. 
 
 4:1. Are there rays in the sunbeam which we can not 
 see? 
 
 We can not see the heat or the chemical rays. 
 
 42. Why, when we press the finger on one eyeball, do 
 we see objects double ? 
 
 Because the rays from the same external object fall on parts 
 of the two retinas that do not correspond in position. 
 
 43. Why does a distant light, in the night, seem like a 
 star ? 
 
 Because its image on the retina is so small that deception 
 becomes easy. 
 
IN POPULAR PHYSICS. 47 
 
 44:. Why does a bright light, in the night, seem so much 
 nearer than it is ? 
 
 We judge of the distance of an object by its magnitude, by 
 its distinctness of outline, and by the size, etc., of intervening 
 objects with which we compare it. In the night, the Ixrightness 
 of a light confuses us by its vividness, seeming to be near at 
 hand. Moreover, we can not see the neighboring objects, whose 
 distance we know or could estimate in the daylight. Our error 
 is therefore one of judgment. 
 
 45. What color predominates in artificial lights ? 
 
 Yellow. 
 
 46. Why are we not sensible of darkness when we 
 wink ? 
 
 Because the wink does not last so long as the impression of 
 the light received just before the wink. 
 
 47. Under ivhat condition do the eyes of a portrait 
 seem to follow a spectator to all parts of a room ? 
 
 This is noticed only in a full-face portrait. In that case the 
 spectator, when he goes to either side, fails to see the side of 
 the eyeballs, and hence the effect is that of looking directly into 
 the eye. "A rifleman, portrayed as if taking aim directly in 
 front of the picture, appears to every observer to be pointing 
 at him specially." 
 
 48. Why do the two parallel tracks of a railroad ap- 
 pear to approach in the distance ? 
 
 The visual angle subtended by the distance between two op- 
 posite points on the tracks becomes less as the distance of the 
 observer increases. 
 
 49. W7iy does a fog apparently magnify objects ? 
 
 It is not the refraction of the rays of light, as is commonly 
 supposed, which makes an object seem larger when seen through 
 a mist. It really appears to us in its proper size. The mist, 
 however, dims the color and the outline, giving it the indis- 
 tinctness belonging to a mile in distance, while it has the mag- 
 nitude of half a mile. Dr. "Wayland relates that, as he was 
 
48 ANSWERS TO PRACTICAL QUESTIONS 
 
 sailing through Newport harbor early one morning, in a dense 
 fog, he observed on the apparently distant wharf some very tall 
 men. While he was remarking upon their extraordinary size, 
 he was astonished to see them jumping about like children, and 
 otherwise behaving in a most unaccountable manner. Pres- 
 ently, as the sun dispersed the fog, he found that he was closo 
 to the wharf, and that the gigantic men were really a party of 
 small boys amusing themselves with play. 
 
 The opposite mistake is made when the atmosphere is more 
 transparent than that to which we are accustomed. Foreign 
 travelers in Switzerland, who have started on foot to visit a 
 glacier or a mountain-peak which seemed within easy distance, 
 have often been surprised to find, after two or three hours of 
 brisk walking, that the object of their desire seemed as far 
 away as at first. So in looking across a sheet of water, where 
 there are no intervening objects, distance is always underrated. 
 
 When we throw a stone at an object in the water we find 
 that our eye has deceived us, and the stone falls far short of 
 the mark. For the same reason, objects seen on the shore from 
 the water seem much less than their natural size. The fact is, 
 they appear of the magnitude which belongs to the distance, 
 but we suppose the distance less than it is ; and, associating 
 tnis magnitude with diminished distance, they appear to us less 
 than they really are. 
 
 In order to form these judgments correctly, one of these 
 elements must be fixed. From this we learn to institute a com- 
 parison, and thus form an accurate opinion. If we know the 
 magnitude of an object, the change in its color and outline will 
 teach us its distance. If we know its distance, we can judge of 
 its magnitude. Hence, painters, in order to give us a correct 
 idea of an object which they represent, always place in its 
 vicinity something with whose real magnitude we are familiar. 
 Thus, to show the size of a pyramid, an Arab with his camel 
 may be drawn at its foot. If the pyramid were represented by 
 itself, its intended size might be mistaken ; but every one knows 
 the size of a camel, and from this he would judge of the mag- 
 nitude of a pyramid. Wayland's Intellectual Philosophy, p. 78, 
 et seq. 
 
IN POPULAR PHYSICS. 49 
 
 50. If yon sit where you can not see another person's 
 image, why can not that person see yours ? 
 
 The angle of incidence is equal to the angle of reflection 
 under all circumstances. If a ray from the other person is not 
 reflected at the right angle to reach your eye, then a ray from 
 you is not reflected at the right angle to reach the other per- 
 son's eye. 
 
 51. IVliy can we see the multiple images in a mirror 
 better if we look into it very obliquely ? 
 
 More light is then reflected to the eye. The ratio of the 
 light reflected to the light refracted increases with the angle of 
 incidence. 
 
 52. Why is an image seen in water inverted ? 
 
 (Examine Fig. 139 in Physics.) 
 
 53. Why is the sun's light fainter at sunset than at 
 midday ? 
 
 (See Physics, p. 191, note.) 
 
 54. WJty can we not see the fence-posts ^vhen we are 
 riding rapidly ? 
 
 Because the images of a succession of objects are formed 
 on the retina at intervals less than that of the duration of a 
 retinal impression. Hence, they all become confused, and noth- 
 ing is seen distinctly. 
 
 55. Ought a red flower to be placed in a bouquet by an 
 orange one ? A pink or blue with a violet one ? 
 
 (Seo Physics, p. 217.) 
 
 These are not complementary colors, and hence do not 
 strengthen each other by contrast. 
 
 56. IVJiy are the clouds ^vhite while the clear sky is 
 blue? 
 
 Prof. Tyndall has shown that the larger particles of vapor 
 scatter light of all colors, i.e., white light; while the smallest 
 particles, only the blue rays. In accordance with this fact, the 
 clouds are white and the sky is blue. If the air were abso- 
 lutely pure, free from all foreign matter, and highly rarefied, 
 
50 ANSWERS TO PRACTICAL QUESTIONS 
 
 it is thought that the azure of the sky would not be seen, and 
 the heavens would appear black : the illumination of objects 
 would be strong and glaring on one side, and on the opposite 
 side the shadows would be deep and unrelieved by the diffused 
 light to which we are accustomed. The minute particles of va- 
 por in the air serve to scatter the direct rays of the sun, and to 
 turn them around corners and into places not in the direct line 
 of the sunlight. 
 
 (See a full and interesting discussion in Tyndall's Lecture on Light, p. 
 152, et seq,) 
 
 57. IVliy does skim -milk look blue and neiv milk 
 white ? 
 
 The fatty globules of the new milk reflect all the colors of 
 the spectrum to the eye ; but when deprived of the cream the 
 milk reflects the blue light in excess of the others. 
 
 58. Why is not the image of the sun in water at mia^ 
 day so bright as near sunset ? 
 
 The angle of incidence being small, most of the light is 
 transmitted, and but little is reflected. Near sunset the greater 
 part is reflected. 
 
 59. Why is the rainboiv always opposite the sun ? 
 
 (See Physics, p. 217.) 
 
 60. Sold a card with its edge close in front of your eye 
 and look at a distant candle flame in a dark room. You 
 will probably perceive either a reddish or a bluish fringe 
 on one side. Explain. 
 
 The crystalline lens is not corrected for chromatic aberra- 
 tion. (See Physics, p. 219.) 
 
 HEAT. 
 
 273 1. Wtiy will one's hand, on a frosty morning, 
 freeze to a metallic door-knob sooner than to one of porce- 
 lain ? 
 
 Because the metal is a better conductor of heat than the 
 porcelain, and hence conducts the heat from the hand faster. 
 
IN POPULAR PHYSICS. 51 
 
 2. Why does a piece of bread toasting curl up on the 
 side toward the fire ? 
 
 The v/ater being expelled from the pores on that side causes 
 
 tho bread to shrink. 
 
 3. Wluj do double ivindoivs protect from the cold ? 
 
 The non-conducting air inclosed between the window-panes 
 keeps in the heat and keeps out the cold. 
 
 4. Why do furnace-men wear flannel shirts in summer 
 to keep cool, and in ivinter to keep warm, ? 
 
 In summer the non-conducting flannel keeps out the fur- 
 nace-heat, and in the winter keeps in the body-heat. 
 
 5. Why do ^ve blow our hands to make them warm, 
 and out- soup to make it cool ? 
 
 Our breath is warmer than our hands, but cooler than our 
 soup. 
 
 6. Why does snow protect the grass in winter ? 
 
 The air inclosed between the flakes of snow is a non-con- 
 ductor. No infant in its cradle is tucked in more tenderly than 
 the coverlet of snow about the humble grass that nestles down 
 for its winter's nap on the bosom of Mother Earth. 
 
 7. Why does water "boil away" more rapidly on 
 some days than on others? 
 
 Because the atmospheric pressure varies, independently of 
 the fact that the source of heat may vary without our noticing it. 
 
 8. What causes the crackling sound in a stove ^vhen a 
 
 fire is lighted ? 
 
 Tho expansion of the iron by the heat. 
 
 ,9. TTh ?//.? the tone of a piano higher in a cold room 
 than in a warm one? 
 
 The steel wires lengthen in a warm room, and so lower the 
 tone. 
 
52 ANSWERS TO PRACTICAL QUESTIONS 
 
 10. Ought an inkstand to have a large or a small 
 mouth ? 
 
 A small mouth, to prevent evaporation. 
 
 11. Why is there a space left between the ends of the 
 rails on a railroad trade ? 
 
 To allow room for the expansion and contraction of the 
 rails with the changes in temperature. 
 
 12. Why is a person liable to take cold when Jiis clothes 
 are damp? 
 
 The water which evaporates from his clothes, in drying, ab- 
 sorbs heat from his body. 
 
 13. What is the theory of corn-popping ? 
 
 The air in the cells of the corn expands by the heat, and 
 bursts the outer coating of the corn. 
 
 14. Could vacuum-pans be employed in cooking ? 
 
 They could not, because the heat would not be sufficient to 
 cook the food. 
 
 15. Why does the air feel so chilly, in the spring, ivhen 
 snow and ice are melting ? 
 
 When the ice is passing into the liquid state, it absorbs heat 
 from all surrounding objects. 
 
 1(>. Why, in freezing ice-cream, do we put the ice in a 
 ivooden vessel, and the cream in a tin one ? 
 
 The non-conducting wooden vessel prevents the ice from ab- 
 sorbing heat from the external air, and the conducting tin ves- 
 sel enables it to absorb the heat from the cream. 
 
 17. Wliy does the temperature generally moderate 
 when the snoiv falls ? 
 
 The vapor passing into the solid form gives off heat. 
 
 19. Why does sprinkling a floor ivith ivater cool the 
 air? 
 
 The water turning to vapor absorbs heat. 
 
IN POPULAR PHYSICS. 53 
 
 20. How low a degree of temperature can be reached 
 with a mercurial thermometer ? 
 
 Nearly to the freezing point of mercury, 39 F. 
 
 21. If the temperature be 7O F., ivhat is it C. ? 
 
 70 -32 = 38. 38-^1.8 = 21.1 C. 
 If the temperature be 7O C., what is it F. ? 
 70 x 1.8 = 126. 126 + 32 = 158 F. 
 
 22. Will dew form on an iron bridge ? 
 Yes, because iron is a good radiator. 
 
 On a planJt walk ? 
 
 Not so readily, because wood is a poorer radiator. 
 
 23. Why will not corn pop when very dry ? 
 
 The pores shrink, and the corn becomes compact ; only por- 
 ous, tender-celled corn will pop. 
 
 24. When the interior of the earth is so hot, why do we 
 get the coldest water from a deep well? 
 
 The well extends below the influence of the sun, and not 
 deep enough to be affected by the internal heat of the earth. 
 
 25. Ought the bottom of a tea-Kettle to be polished ? 
 
 No, since a polished surface would reflect the heat. We 
 need a black, rough, sooty surface to absorb the heat rapidly. 
 
 26. Which boils the sooner, milk or water ? 
 
 Milk, because it is so adhesive that the bubbles of steam 
 which are formed at the bottom of the dish can not easily es- 
 cape. They therefore pile up on top of each other, and the 
 milk boils over readily. 
 
 27. Is it economy to keep our stoves highly polished? 
 
 The stove-blacking used is a good radiator, but the surface 
 should not be highly polished, as that hinders radiation. 
 
 28. If a thermometer be held in a running stream, will 
 it indicate the same temperature that it would in a pailful 
 of the same ivater ? 
 
54 ANSWERS TO PRACTICAL QUESTIONS 
 
 It will. For the same reason that a thermometer, in the 
 wind, will indicate the same temperature as in the still air, al- 
 though the former seems to us much colder. 
 
 29. Which makes the better holder when one wishes to 
 protect his hands from a hot dish, woolen or cotton ? 
 
 Woolen, because it is so poor a conductor of heat. 
 
 30. Which ivill give out the more heat, a plain stove or 
 one with ornamental designs ? 
 
 The latter, since it has more radiating surface. 
 
 31. Does dew fall? 
 
 No; it forms directly where it is found. The vapor merely 
 collects on the cold surface. 
 
 32. What causes the " sweating " of a pitcher ? 
 
 The vapor of the air condenses on the cold pitcher. It is 
 often a sign of rain, since it shows that the air is full of vapor 
 easily deposited. 
 
 33. Why is evaporation hastened in a vacuum ? 
 
 Because the pressure of the air is removed. 
 
 34. Does stirring the ground around plants aid in the 
 deposition of dew ? 
 
 It does, since it facilitates radiation. 
 
 35. Wliy does the snow at the foot of a tree melt sooner 
 than that in the open field ? 
 
 The tree absorbs the sun's heat, and then radiates it out, 
 thus serving as a carrier for the snow. 
 
 36. WJty is the opening in a chimney made to decrease 
 in size from bottom to top ? 
 
 Because as the heated air rises it cools and shrinks. If 
 the chimney did not diminish in size correspondingly, currents 
 of cold air would set down from the top. 
 
 37. Will tea keep hot longer in a bright or in a dull 
 tea-pot ? 
 
J.V POPULAR PHYSICS. 55 
 
 In a bright one, since a polished surface retards radiation. 
 
 38. JJJiat causes the snapping of wood when laid on 
 the fire? 
 
 The expansion of the air in the cells of the wood. 
 
 39. Why is one's breath visible on a cold day ? 
 
 The vapor in the breath is condensed by the cold air. 
 
 40. What gives tlie blue color to air ? 
 
 The particles floating in it reflect the blue light of the sun- 
 beam. 
 
 4:1. How does the heat at two feet from the fire compare 
 with that at four feet? 
 
 2* ; 4 2 ; : 1 : 4. 
 Hence it is four times greater. 
 
 4=2. Why does the frost remain later in the morning 
 upon some objects than upon others ? 
 
 The best radiators are the best absorbers. They become 
 warmed by the morning sun more quickly than the poorer 
 radiators, and the frost on them is hence more quickly melted. 
 
 43. Is it economy to use green ivood ? 
 
 No. Its sap has to be changed to vapor, thus absorbing a 
 large amount of energy at the expense of the combustion. 
 
 44. Why does not green wood snap ? 
 
 The pores are filled with water instead of air. The water 
 does not expand rapidly enough to burst off the coverings of 
 the cells, and so simply oozes out gradually, and is vaporized. 
 
 45. Wliy will a piece of metal dropped into a glass or 
 porcelain dish of boiling ivater facilitate the ebullition ? 
 
 The rougher surface of the metal aids in the formation 
 and disentanglement of the steam-bubbles. The bubbles cling 
 longer to a smooth than to a rough surface. This is one 
 cause of that bumping sound often noticed when liquids are 
 boiling in glass dishes. 
 
56 ANSWERS TO PRACTICAL QUESTIONS 
 
 46. Which can be ignited the more easily 'with a burn- 
 ing-glass, black or white paper ? 
 
 Black paper, since it is a much better absorber of heat. 
 
 47. Why does the air feel colder on a windy day ? 
 
 Because fresh portions of cold air are brought constantly in 
 contact with our bodies. 
 
 48. Could a burning-lens be made of ice ? 
 
 Burning-lenses have been made of that material. The rays 
 have no heating power until the waves of ether are stopped. 
 They do not elevate the temperature of the medium through, 
 which they pass. 
 
 49. IVhy is an iceberg frequently enveloped by a fog ? 
 
 The moisture of the air is condensed upon its cold surface. 
 
 50. Would dew gather more freely on a rusty stove 
 than on a bright Kettle ? 
 
 It would, because the rusty iron surface is a good radiator. 
 
 51. Why is a clear night colder than a cloudy one dur- 
 ing the same season ? 
 
 On a cloudy night the clouds reflect the radiated heat of the 
 earth back again, and thus act as a blanket to keep the earth 
 warm. On such a night there can be no frost or dew. On a 
 clear night, the heat which the earth radiates passes out freely 
 into space, and thus the earth cools rapidly. 
 
 52. Why is no dew formed on cloudy nights ? 
 
 See last question. 
 
 53. Why will "fanning " cool the face ? 
 
 It brings in contact with the face a current of fresh and 
 generally cooler air. 
 
 54. How are safes made fire-proof? 
 
 By filling the space between the inner and the outer iron 
 plates with a non-conducting material, as plaster, etc., the safe 
 is rendered nearly fire-proof. 
 
IN POPULAR PHYSICS. 57 
 
 55. Why can you heat water quicker in a tin than a 
 china cup ? 
 
 Because the metal is a better conductor of heat than the 
 china. 
 
 56. WJiy will a woolen blanket keep ice from melting ? 
 
 The woolen is a non-conductor of heat. 
 
 57. Does dew form under trees ? 
 
 The trees reflect back the heat radiated by the earth, grass, 
 etc., and so prevent the temperature, in general, from sinking 
 to the dew-point. 
 
 58. Wliat is the principle of heating by steam ? 
 
 The steam is condensed in the pipes, and gives out as tem- 
 perature the energy which had been previously absorbed in 
 changing water to steam. 
 
 59. IFJiat is the cause of " cloud-capped " mountains ? 
 
 The warm, moist air from the valleys rises against the 
 mountain sides. Its vapor, previously invisible, becomes con- 
 densed by the colder air into a cloud of droplets that float in 
 the air. 
 
 60. Show how the glass in a hot-house acts as a trap to 
 
 catch the sunbeam. 
 
 (See Physics, p. 259.) 
 
 61. Does the heat of the sun come in through our ivin- 
 
 doivs ? 
 
 (See Physics, p. 259.) 
 
 62. Does the heat of our stoves pass out in the same 
 
 tvay ? 
 
 (See Physics, p. 259.) 
 
 63. TJie top of a mountain is nearer the sun; why is it 
 
 not ivarmer ? 
 
 (See Physics, pp. 250 and 200.) 
 
 67. Can we find frost on the ivindows and on the stone- 
 flagging the same morning ? 
 
 It requires a much intenser cold to produce the former ef- 
 fect than the latter, as glass is a poorer conductor of heat than 
 
58 ANSWERS TO PRACTICAL QUESTIONS 
 
 stone. We frequently find frost on the nagging early in the 
 fall, but frost on the window is a sign of very severe winter 
 weather. 
 
 68. IFhy will not snow "pack" into balls except in 
 mild weather ? 
 
 The snow must be very near the melting-point for the press- 
 ure of the hand to be sufficient to melt enough of it to pro- 
 duce the phenomena of regelation. (Physics, p. 271, 1st note ; 
 also Tait's Recent Advances in Physical Science, p. 129, and 
 Tyndall's Forms of Water, p. 163.) This principle involves the 
 theory of Glaciers. " The masses of snow can not rest on the 
 steep slopes of Alpine summits. The pressure upon the under 
 layers is too great to allow them to remain upon their sloping 
 beds, and they are forced to descend. This descent is accom- 
 plished in two forms : that of an avalanche, one of the most 
 awful and imposing spectacles to witness ; or of a glacier, 
 which is really an avalanche of ice of extremely slow motion. 
 But the glacier differs from the ordinary avalanche not only in 
 that its motion is so slow, but in that it consists of ice, thick, 
 firm, and hard. The principles involved in this transition of 
 the loose, flaky snow which first falls upon the mountain-top 
 into the solid ice of the glacier, are very well illustrated, as 
 Helmholtz has remarked, in the manufacture of the school- 
 boy's snow-ball or snow-man. Very cold snow is always light 
 and flaky, and can not be made by the pressure of the hands 
 into a cohesive mass ; in order to succeed in that operation, 
 snow is always employed which is already at the melting-point, 
 or only so far below this temperature that the warmth of the 
 hand suffices to bring it to the required temperature, and then, 
 by dint of pressure and molding, an icy ball may be easily 
 produced. So with the formation of the glacier ice. A process 
 of almost simultaneous melting and freezing goes on among 
 the under layers of snow, and under an immense and ever- 
 constant pressure from the weight of the snow above ; thus 
 solid ice is formed. That this ice conforms itself to the various 
 windings, constrictions, and dilatations of its rocky channel 
 during its downward march, is a fact not less familiar than 
 wonderful." 
 
IN POPULAR PHYSICS. 59 
 
 69. WJiy is the sheet of zinc under a stove so apt to be- 
 come puckered ? 
 
 When zinc cools after expansion it does not return quite to 
 its former dimensions, and so becomes " puckered," as it is 
 called. 
 
 70. WJiy does a mist gather in the receiver of the air- 
 pump as the air becomes rarefied ? 
 
 "The remaining air, cooled by rarefaction, absorbs heat 
 from the invisible vapor in combination with it, and renders 
 the water visible. The mist may be removed by continued ac- 
 tion of the machine, or by re-admitting the normal quantity of 
 air." 
 
 (See Arnott's Physics, p. 448.) 
 
 71. Why are the tops of high mountains in the tropics 
 covered ivith perpetual snow ? 
 
 See question 59. 
 
 MISCELLANEOUS QUESTIONS AND 
 PROBLEMS FOE REVIEW. 
 
 1. Does a plumb - line point to the earth's center of 
 figure or center of gravity ? 
 
 2. In a dark room, let the light of a candle pass through 
 a small hole in a card, and the image of the candle on the 
 opposite wall will be inverted. Explain. 
 
 3. How many titties heavier is the earth than an equally 
 large globe of water? 
 
 4:. Why does a rocket ascend into the air ? 
 
 5. Is the water at the foot of Niagara Falls warmer 
 than that in the river above ? 
 
 f>. What causes wheel fire-works to rotate ? 
 
 7. A brass rod covered tightly with thin paper may be 
 held some time in a flame ivithout the paper being scorched; 
 while, if the rod be of wood, the paper will scorch at once. 
 Wliy is this difference? 
 
60 MISCELLANEOUS QUESTIONS. 
 
 8. How would it affect the action of a siphon if it ivere 
 carried up a mountain ? 
 
 9. If a vessel of water containing a floating body be 
 placed under the receiver of an air-pump, and the air 
 gradually exhausted, what will be the effect on the floating 
 body? 
 
 10. How will it change the height of the column of 
 mercury in a barometer to incline the tube ? 
 
 11. In the image of a written page seen in a mirror, 
 why does the writing seem to slope ? 
 
 12. Why does a coin placed in a tumbler look larger 
 when the glass is full of water than when it is empty ? 
 
 13. Two bodies of different volume iveigh the same in 
 water ; which will weigh the more in mercury, the larger 
 or the smaller ? 
 
 14:. How does the wind drift sand, snow, etc. ? 
 
 15. Why does oil " still troubled waters" ? 
 
 16. Why does crouching down at the highest points in 
 a swing, and standing up at the lowest point, increase the 
 velocity ? 
 
 17 What difference would it make in the guinea-and- 
 feather experiment to force into the tube additional air, 
 instead of exhausting it, as ordinarily done ? 
 
ANSWERS 
 
 TO THE 
 
 PRACTICAL QUESTIONS AND PROBLEMS 
 
 IN 
 
 STEELE'S POPULAR CHEMISTRY. 
 
 [The large figures refer to the page of the Chemistry, and the small 
 ones to the number of the questions.] 
 
 26 ! What becomes of the ivater that " dries up " ? 
 Of the wood that " burns up " ? Is there any destruction 
 of the matter they contain ? 
 
 The water is changed into invisible vapor, and wafted thus 
 away. 
 
 The wood is oxidized into CO 3 and H 2 O, which mingle with 
 the air. The ashes consist of SiO 2 , K 2 CO 3 , and the oxides of 
 any other elements present whose compounds with O are not 
 gaseous. 
 
 There is no destruction of the matter contained. 
 
 2. Where is the higher oxide formed, at the forge or in 
 the pantry ? 
 
 There is more complete oxidation at the forge. At low 
 temperatures, decomposition results often in complex products. 
 
 3. Wlty is the blood red in the arteries, and darle in the 
 veins ? 
 
 When specimens of venous and of arterial blood are sub- 
 jected to chemical examination, the differences presented by 
 their solid and fluid constituents are found to be very small and 
 inconstant. As a rule, there is rather more water in arterial 
 blood, and rather more fatty matter. But the gaseous contents 
 of the two kinds of blood differ widely in the proportion which 
 
62 ANSWERS TO PRACTICAL QUESTIONS 
 
 the carbonic acid gas bears to the oxygen ; there being a smaller 
 quantity of oxygen and a greater quantity of carbonic acid, in 
 venous than in arterial blood. And it may be experimentally 
 demonstrated that this difference in their gaseous contents is 
 the only essential difference between venous and arterial blood. 
 For if arterial blood be shaken up with carbonic acid, so as to 
 be thoroughly saturated with that gas, it loses oxygen, gains 
 carbonic acid, and acquires the hue and properties of venous 
 blood ; while, if venous blood be similarly treated with oxygen, 
 it gains oxygen, loses carbonic acid, and takes on the color and 
 properties of arterial blood. HUXLEY'S Lessons in Physiology. 
 
 . Do we need more O in ^v^nter than in summer ? 
 
 Yes, if we are much exposed to the open air, and forced to 
 take abundant exercise in order to keep warm. 
 
 5. Wliicli would starve sooner, a fat man or a lean 
 one ? 
 
 The lean one. A superabundance of flesh, in a time of 
 scarcity, is taken up by the absorbents and thrown into the 
 circulation, thus supplying the place of food in nourishing the 
 body. 
 
 6. How do teamsters ^varm themselves by slapping 
 their hands together' ? 
 
 This exercise promotes the circulation of the blood, and its 
 oxidation is thus quickened. 
 
 7. Could a person commit suicide by holding his 
 breath ? 
 
 Respiration is entirely independent of consciousness, as is 
 seen in sleep, coma, etc. It may be interrupted for a few min- 
 utes, but no effort of the will can enable one to hold his breath 
 until life is extinct. The desire for O, the besoin de respirer, or 
 the respiratory sense, as it is called, becomes at last so great 
 that the strongest resolution yields the struggle. 
 
 8. Wiy do we die ivhen our breath is stopped ? 
 
 " In asphyxia it is difficult to say which destroys life, the 
 absence of oxygen or the presence of carbonic acid." FLINT. 
 
IN POPULAR CHEMISTRY. 63 
 
 There is an absence of oxygen, so essential to every vital 
 operation, and also an accumulation of carbonic acid in the 
 system. 
 
 0. Wiiy do we breathe so slowly when ive sleep ? 
 
 The circulation is less rapid, and various functions of the 
 body are less active. There is hence less need for rapid oxi- 
 dation. 
 
 10. Hoiv does a cold-blooded animal differ from a 
 warm-blooded one ? 
 
 In the imperfection with which the blood is oxygenated. 
 The lungs are often of small capacity, and loose texture, and 
 are sometimes wanting entirely. In reptiles a portion of the 
 blood is not sent to the heart, and hence in the vessels there is 
 a mixture of arterial and venous blood. The breathing is there- 
 fore slow, the motions are languid, and there is little heat. 
 
 11. Why does not the body burn otit like a candle ? 
 
 Because it is renewed by the processes of assimilation and 
 nutrition as rapidly as it is destroyed by the waste of oxida- 
 tion. Whenever the former are in excess we gain flesh ; when 
 the latter, we grow poor. 
 
 12. Do all parts of the body change alike? 
 
 The rate of change varies with the amount of oxidation, 
 and that depends on the use of the organ. The right arm of 
 the blacksmith must be transformed much more rapidly than 
 the left. 
 
 13. WJiat objects would escape combustion if the air 
 were undiluted O ? 
 
 Burnt bodies, i.e., those which are already combined with 
 oxygen. 
 
 14. Why is it difficult to obtain O from the air ? 
 
 Because, although free from combination, it is intimately 
 mixed with N. 
 
 15. What ^veight of O can be obtained from 1O (/rams 
 ofHgO? 
 
64 AtfSWEXS TO PRACTICAL QUESTIONS 
 
 HgO : O : : 10 : jr. 
 216 : 16:: 10: a:. 
 
 16x10 
 
 x = 216 =.74: + , grams. 
 
 16. How much O can be obtained from 6 grains of 
 KCIO 3 ? 
 
 KC1O 3 : O 3 : : 6 : x. 
 122.5 : 48 : : 6 : x. 
 
 17. Hoiv much KCIO Z would be needed to produce 2 
 kilograms of O ? 
 
 3 : KC10 3 : : 2 : x. 
 48 : 122.5 : : 2 : x. 
 
 122.5x2 
 
 x = - j^ - = 5.1 + , kilograms. 
 
 18. How much KCl would be formed in preparing 1 
 kilogram of O ? 
 
 Hence, O 3 : KCl : : 1 : x. 
 
 48 : 74.5 : : 1 : x. 
 74 5 
 x = -j^- = 1.55 + , kilograms. 
 
 19. Is it probable that all the elements fire discovered? 
 
 No. But all new elements lately discovered have proved to 
 be chemical rarities. Probably all of the abundant and gener- 
 ally useful elements have been discovered. 
 
 20. Is heat produced by oxidation ? 
 
 It is a manifestation of chemical change. In this sense it 
 may be considered to be caused by it. 
 
 21. What is the difference betiveen kinetic and potential 
 energy ? 
 
 Kinetic energy is energy of motion ; potential energy is 
 that of position. (Consult Steele's Popular Physics, p. 35.) 
 
 22. ^Vliy does running cause pantiny ? 
 
IN POPULAR CHEMISTRY. 65 
 
 One of several causes is the need of more O to supply the in- 
 creased oxidation in the blood necessitated by unusual exertion. 
 
 23. How does O give us strength ? 
 
 Our muscles, as well as the food from which they are 
 formed, consist of complex molecules. When they are oxidized, 
 potential energy becomes kinetic. 
 
 24. Does the plant produce energy ? ' 
 
 No ; it only absorbs solar energy, and becomes the medium 
 of its transformation. 
 
 25. If we 1>nrn an organic body in a stove it gives off 
 heat; in the animal body it produces also motion. Ex- 
 plain. 
 
 The force set free by the oxidation of the muscles, and of 
 the food within the body, is converted into muscular energy. 
 
 2(>. Why does not blowing cold air on, a fire ivith a bel- 
 lows extinguish it ? 
 
 It may extinguish it if the blast be strong enough. If not 
 strong enough to cool it below its kindling point, the heat of 
 oxidation more than balances the cooling from the air. 
 
 27. IVJiy docs bloiving on a fire hlndle it, and on a 
 lighted lamp extinguish it ? 
 
 The answer to the previous question applies to this one also. 
 
 28. Why can we not ignite hard coal with a match ? 
 
 The heat of the match is not enough to decompose the coal, 
 and thus set free gaseous constituents for the production of flame. 
 
 29. Why ivill an excess of coal put out a fire ? 
 
 The coal is heated at the expense of the fire, and may reduce 
 this below the kindling point unless the supply of O is rapid. 
 
 30. Could a light be extinguislied by merely lowering 
 the temperature ? 
 
 Yes ; by contact of a large body that is a good conductor 
 of heat. 
 
66 ANSWERS TO PRACTICAL QUESTIONS 
 
 31. Why is it beneficial to stir a wood-fire, but not one 
 of anthracite coal? 
 
 The gaseous constituents of wood are more easily separated 
 than those of coal, but the heat evolved in combustion is less. 
 When once well started, the combustion of the coal is hence 
 more apt to be self-sustaining. 
 
 32. Why ivill water put out a fire ? 
 
 It absorbs more heat in proportion to its weight than any 
 other known substance does in changing from liquid to gas. 
 The production of steam is hence at the expense of the heat of 
 combustion, and the fuel is soon cooled below its kindling point. 
 
 33. What should we do if a person's clothes talce fire ? 
 
 Smother the flame by wrapping the person as quickly as 
 possible with a rug, coat, blanket, or any thing of this kind that 
 may be at hand. If water be near, throw it abundantly on 
 the burning garment. . . 
 
 34. Ought the doors of a burning house to be thrown 
 open? 
 
 No, except for the purpose of getting out of it. The in- 
 creased supply of air through the opening promotes the com- 
 bustion. 
 
 35. Hoiv much O can be obtained from 1OO grams of 
 
 Iff/0? 
 
 HgO : O : : 100 : x. 
 
 216 : 16 : : 100 : x. 
 x = 7.4+, grams. 
 
 30. What would be the volume of the O of Question 35 
 under the standard conditions ? 
 
 7.4-*- 1.43 = 5.17 liters. 
 
 37. JVJiat would be the volume of the O at 12 C. and 
 under a pressure of 74O mm. of mercury ? 
 
 x = * x 5 - 17 = 5 - 42 + ' liters - 
 
IN POPULAR UHEMISTKT. 67 
 
 38. What would be the volume of the O of Question 16 
 tit 2O* C. and 75O nun. ? 
 
 1.55 293 760 
 
 39. How much KCIO S must be employed to maize an 
 amount of O which shall measure 1OO liters at 18 C. and 
 7<>O mm. ? 
 
 First find how many liters of O under standard conditions 
 wo aid be expanded to 100 liters at 18 C., the given pressure, 
 760 mm., being itself standard. Call the result V. It is 
 
 273_x_100 
 ~291 * 
 
 Each of these liters weighs 1.43 grams ; hence, the total 
 
 weight is 
 
 27,300x1.43 
 
 291 
 
 Let x = the required weight of KC1O 3 . 
 Then 3 : KC1O 3 : : W : x. 
 
 27,300x1.43 
 48: 122.5:: -- ^_ - : x. 
 
 Hence, _ 27,300x1.43x122.5 
 
 ~291x48 
 
 x = 342.4 grams. 
 
 371. Hoiv could you detect any free O in ajar ofN? 
 
 By passing into it some NO (see p. 34). It will combine 
 with the free O, forming red fumes of NO a . 
 
 2. Hoiv would you remove the product of the test ? 
 
 By allowing the mixture to stand over water, which will 
 dissolve the NO 2 . 
 
 3. In the experiment shown in Fig. ,9, why is the gas 
 red in the flask, but colorless when it bubbles up into the 
 jar ? 
 
68 AXSWRRS TO PRACTICAL QUESTIONS 
 
 In the flask, one fifth of the atmosphere was free O, which 
 produces NO a with the NO as soon as this is evolved. In the 
 jar there is no free O. 
 
 4. How much NH 3 can be obtained from 3 {/rams of 
 sal-ammoniac ? 
 
 From the reaction, 2NH 4 Cl + CaO = 2NH 3 + H 2 O + CaCl 2 , we 
 see that for every molecule of NH 4 C1 used we obtain one mole- 
 cule of NH 3 . Hence, 
 
 NH 4 C1 : NH 3 : : 3 : x. 
 53.5 : 17 : : 3 : x. 
 x = .95 + , gram. 
 
 ft. What will be the volume of the NH Z at 2O C. and 
 770 mm. ? 
 
 Taking H as our standard, the density of NH 3 is half its 
 molecular weight, or : ^ , = 8.5. The density of O is 16, and 
 a liter of it weighs 1.43 grams. Hence, a liter of NH 3 weighs 
 -jr xl.43 grams, or almost exactly .76 gram. The volume oc- 
 cupied by .95 gram of NH 3 under standard conditions is hence 
 
 '-153 of a liter, or 1.25 
 .76 
 
 quired volume will be 
 
 '-153 of a liter, or 1.25 liters. At 20 C. and 770 mm. the re- 
 .76 
 
 _293 760 
 
 ~273 X 770 ' 
 
 x = 1.324 liters. 
 
 0. How much H 2 O will be formed in the process? 
 
 From the reaction we see that one molecule of H 2 O is 
 formed for two molecules of NH 4 C1. Hence, 
 
 2NH 4 C1 : H 3 O : : 3 : x. 
 107 : 18 : : 3 : x. 
 
 7. How much CaO ivlll be needed ? 
 
 From the reaction we see that one molecule of CaO is re- 
 quired with two molecules of NH 4 C1. Hence, 
 
IX POPULAR CHEMISTRY. 69 
 
 2NH 4 C1 : CaO : : 3 : a?. 
 107 : 56 : : 3 : cc. 
 
 x = 1.57 grams. 
 
 S. How much N 2 Ocanbe made from 1 gram of am- 
 monium nitrate ? 
 
 The reaction is 
 
 NH 4 NO 3 = 2H 2 O + N 2 0. 
 Hence, NH 4 NO 3 : N S O : : 1 : x. 
 
 80 . 44 : : 1 : x. 
 x = .55 gram. 
 
 .9. How much nitric acid can be formed from 5O kilos 
 of sodium nitrate (NaNO*)? 
 
 The reaction is 
 
 Hence, NaNO 3 : HNO 3 : : 50 : x. 
 
 85 : 63 : : 50 : x. 
 x = 37 + , kilograms. 
 
 1 O. What causes flesh to decompose so much more easily 
 than wood ? 
 
 It is partly owing to the greater complexity of its molecule, 
 and partly to the presence of the N, which is very unstable in 
 its compounds. 
 
 11. If a tuft of hair be heated wi a lest tube, the liquid 
 formed ivill turn red litmus-paper blue. Explain. 
 
 Ammonia is formed by the decomposition of the hair, and 
 this acting on the red litmus-paper, turns it blue. 
 
 12. Why should care be used in opening a bottle of 
 strong H 3 N in a warm room? 
 
 The space above the liquid is filled with ammonia gas, 
 which had been dissolved in the water at a low temperature. 
 Its expansive force is greatly increased when the temperature 
 is raised. When the stopper is removed, therefore, a concussion 
 may result. 
 
70 ANSWERS TO PRACTICAL QUESTIONS 
 
 13. What weight of Nis there in 1O grams of HNO Z ? 
 
 HNO 3 : 1ST : : 10 : x. 
 63 : 14 : : 10 : x. 
 x = 2.2 grams. 
 
 14. Hoiv much sal-ammoniac would be required to 
 make 2O liters of NH Z measured at 25 C. and 744 mm. ? 
 
 Refer to the answer of Question 5. A liter of NH 3 under 
 standard conditions weighs .76 gram. 
 
 First find how many liters of NH 3 at C. and 760 mm. 
 are required to expand to 20 liters at 25 C. and 744 mm. 
 Call the result V. Then 
 
 Each of these weighs .76 gram. Call the result W. 
 Then NH 3 - NH 4 C1 : : W : x. 
 
 17 . ' 107 ..273x744x20x.76 
 
 298 x 760 
 - 107 x 273 x 744 x 20 x. 76 
 
 17x298x760 
 x = 85.8 grams. 
 
 15. What is the difference between liquid ammonia and 
 liquor ammonice ? 
 
 Liquid ammonia is the result of condensing the gas by cold. 
 Liquor ammoniae is the commercial name often applied to the 
 solution of the gas in water. 
 
 52 1. Why, in filling the hydrogen gun, do ive use 5 
 parts of common air to 2 of II, and only one part of O to 2 
 ofH? 
 
 Because the air is only oxygen, and hence 5 parts of com- 
 mon air are equivalent to 1 part oxygen. 
 
 2. Why are coal cinders often moistened with H s O be- 
 
 fore using ? 
 
 (See Popular Chemistry, p. 45, note.) 
 
 The H 2 O being decomposed by the heat of the fire increases 
 the combustion. 
 
IN POPULAR CHEMISTRY. 71 
 
 3. IFJiat injury may be done by throwiny a small quan- 
 tity of H 2 O on a fire ? 
 
 "No more heat is produced by the action of the H 2 O, but 
 it is in a more available form for communicating heat. The 
 steam in contact with incandescent charcoal is decomposed the 
 O going to the C to form CO 2 , and the H being set free. If 
 the C is abundant, and the heat high, the CO 8 is also decom- 
 posed, and double its volume of CO formed. The inflammable 
 gases, H and CO, mingled with the hydrocarbons always pro- 
 duced, are ignited, making the billows of flame which sweep 
 over a burning building." S. P. SHARPLES. 
 
 4. IVliy does the hardness of ^vater vary in different 
 localities ? 
 
 The hardness of the water will necessarily vary with the 
 solubility of the minerals in different localities. 
 
 5. What causes the variety of minerals in the ocean ? 
 Is the quantity increasing ? 
 
 The ocean contains the washings of the land. Every min- 
 eral soluble in water is borne to the sea. The quantity of min- 
 eral matter in the ocean would therefore seem to be increasing, 
 yet there is a compensation in the return to the soil, of guano, 
 marine plants, and fish, which are driven on shore by winds 
 and waves, or carried by the industry of man. 
 
 Analysis of sea- water (Schweitzer) : 
 
 Water 063. 74 
 
 Sodium chloride 28.05 
 
 Potassium chloride ... .76 
 
 Magnesium chloride 3.66 
 
 Magnesium bromide .02 
 
 Magnesium sulphate 2.29 
 
 Calcium sulphate 1.40 
 
 Calcium carbonate , .03 
 
 Iodine traces 
 
 Ammonia traces 
 
 1,000.00 
 
 6. Is there not a compensation in the sea-plants, fish, 
 etc., which are washed back on the land ? 
 
 (See Answer to Question 5.) 
 
72 ANSWERS TO PRACTICAL QUESTIONS. 
 
 7. Since " all the rivers flow to the sea/' ivliy is it not 
 full? 
 
 Because of the constant evaporation from its surface. 
 
 8. What is the cause of the tonic influence of the sea- 
 breeze? 
 
 There are traces of certain minerals which probably give to 
 the sea-breeze a bracing influence. The air from the ocean is 
 also, doubtless, highly ozonized. It is free from the contamina- 
 tions that so often make the atmosphere of the cities and parts 
 of the country unhealthy. 
 
 9. When fish are taJcen out of the water, and thus 
 brought into a more abundant atmosphere, ivhy do they 
 die? 
 
 Fish inhale O through the fine, silky filaments of their gills. 
 When a fish is drawn out of H 2 O, these dry up, and it is un- 
 able to breathe, although it is in a more plentiful atmosphere 
 than it is accustomed to enjoy. 
 
 1 0. Do all fish die ivhen brought on land ? 
 
 No. Some fish have an apparatus for moistening their gills. 
 They can therefore crawl about in the grass, and even migrate 
 from one stream to another. 
 
 1 /. What weight of water is there in 1OO Ibs. of sodium 
 sulphate (Na 2 SO 4 , 1OH 2 O), or Glauber 9 s salt? 
 
 10H 2 O : Na s SO 4 , 10H,O : : x : 100 Ibs. 
 180 : 322 : : x : 100 Ibs. 
 
 322 x = 18,000 Ibs. 
 
 a = 55.9 Ibs. (H 2 O). 
 
 J2. Wliat weight of water in a ton of alum (KA1 9 
 12H 2 O}? 
 
 12H 3 O : KA1, 2SO 4 , 12H 2 O : : x : 2,000 Ibs. 
 216: 474.5 : : x : 2,000 Ibs. 
 
 474.5 x = 432,000 Ibs. 
 
 x = 910.4 Ibs. (H 2 O). 
 
 13. How does the air purify running water? 
 
IN POPULAR CHEMISTRY. 73 
 
 The O contained in the air absorbed by the H 2 O oxidizes 
 the organic substances, which are the most dangerous impuri- 
 ties. 
 
 14:. WJiatis the action of potassium, permanganate as 
 a disinfectant ? 
 
 It gives up its O to oxidize the organic impurities. 
 
 15. What weight of II can be obtained from a liter of 
 water ? 
 
 The weight of a liter of water under standard conditions is 
 1,000 grams. Of this is H. Hence, the required weight is 
 grams. 
 
 16. Hoiv much Zn must be employed to obtain 1OO 
 grams of H from H<>SO ? 
 
 The reaction is 
 
 Zn + H 8 SO 4 = ZnSO 4 + 2H. 
 Hence, 2H : Zn : : 100 : x. 
 
 2 : 65 : : 100 : x. 
 x = 3,250 grams. 
 
 17. A liter of H under standard conditions weighs 
 O.O896 grant. What volume of Hat 1O C. and 738 mm. 
 can be obtained from H^SO^ by the action of 8 Jcilos of 
 
 Zn? 
 
 Zn + H 2 SO 4 = ZnSO 4 + 2H. 
 
 Zn : 2H : : 8,000 : x in grams. 
 65 : 2 : : 8,000 : x. 
 
 x = 246.15 grams. 
 
 The number of liters under standard conditions is 
 246.15 
 .0896 ' 
 
 At 10 C. and 738 mm., the volume is 
 _ 246.15 283 760 
 " 70896" X 273 X 738' 
 V = 2932.7 liters. 
 
 IS. How much KCIO 3 would be required to evolve suffi- 
 cient O to burn the H produced by the decomposition of 2 
 grams of H Z O? 
 
74 ANSWERS TO PRACTICAL QUESTIONS 
 
 The weight of H from 2 grams of H 2 O is f gram. The 
 weight of O required to unite with it is 8xf, or - 1 /- giam. 
 
 3O : 
 
 48: 122.5 ::%-: x. 
 x = 4.537 grams. 
 
 19. How much O would be required to oxidize the me- 
 tallic Cu which could be reduced from its oxide by passing 
 over it 9 when ivhite-hot 9 2O grams of H gas? 
 
 The amount required to oxidize the Cu is obviously the 
 same as that which would be separated from the CaO by re- 
 duction. The number of grams of O thus separated must be 8 
 times the weight of the H, or 160 grams. 
 
 20. How much O would be required to oxidize the me- 
 tallic Fe which could be reduced in the same manner by 1O 
 grams of H gas ? 
 
 To oxidize 10 grams of H would require 80 grams of O. If 
 this be withdrawn from the oxide of iron, the same amount 
 would be required to oxidize the iron thus reduced. 
 
 21. Why are rose-balloons so buoyant ? 
 
 Because the H which they contain displaces air that is 
 more than 14 times as heavy. 
 
 22. How much H must be burned to produce a ton of 
 water ? 
 
 A ton is 2,000 pounds. The weight of H in a ton of watei 
 is $ x 2,000, or 222f pounds. To find the volume of this we re^ 
 member that the weight of 100 cubic inches of air is 31 grains 
 (see Popular Physics, p. 131). In every 5 parts of air there are 
 4 parts of 1ST, weighing 14 times as much as the same volume 
 
 of H, and 1 part of O, weighing 16 times as much ; ~ -- 
 
 o 
 
 = 14.4, nearly. Hence, air is about 14.4 times as heavy as H. 
 Therefore 31 grains will be the weight of 100 x 14.4 cubic 
 
 inches of H, or of ^-=~- Q of a cubic foot of H. To reduce the 
 
 i, i ,00 
 
77V POPULAR CHEMISTRY. 
 
 7o 
 
 given weight, 222| pounds, to grains, we multiply by 7,000, the 
 
 14,000,000 
 number of grains in a pound, making : ^ grains. 
 
 Then 
 
 14,000,000 1,440 
 
 9 
 
 : x in cubic feet. 
 
 9 ' ' 1,728 
 x 41,817 cubic feet. 
 
 This would be enough to fill a spherical balloon 43 feet in 
 diameter. 
 
 84 1. IVliy will pine-wood ignite more easily than 
 maple ? 
 
 It is richer in hydrocarbons, that are readily volatile. 
 
 2. Wliy is fire-damp more dangerous tlian cholte- 
 damp ? 
 
 Fire-damp, CH 4 , contains no O. At the appropriate tem- 
 perature of kindling, when mixed with air, it is a dangerous 
 explosive. Choke-damp, CO 2 , is already a stable compound con- 
 taining the largest proportion of O that can unite with C. It 
 is, therefore, not explosive. 
 
 3. Hepresent the reaction in malting CO 2 , shoiving the 
 atomic weights, as in the preparation of O on page 12. 
 
 (40+12 + 48) + 2 (1 + 35. 5) = (40 + 71) + (2 + 16) + (12 + 32). 
 100 + 73 = 111 + 18 + 44. 
 173 = 173. 
 
 4. Should one taJce a light into a room where the gas is 
 escaping ? 
 
 No. An important constituent of illuminating gas is the 
 dreaded fire-damp, CH 4 . Mixed with the air in the room, it 
 may be exploded by introducing a lighted match or candle. 
 
 5. irtiy does it dull a Jcnife to sharpen a pencil ? 
 
 The particles of graphite in the pencil are very hard, and 
 the knife edge is worn away by friction. 
 
 6. Where was the C, now contained in the coal, before 
 the Carboniferous age ? 
 
 Probably most of it was combined with O, forming CO 3 in 
 a densely charged atmosphere. 
 
76 ANSWERS TO PRACTICAL QUESTIONS 
 
 7. Must the air have then contained more 2>lctnt food ? 
 
 Probably it did. 
 
 8. What is the principle of the aquarium ? 
 
 The inter-dependence of animals and plants, whereby each 
 supplies the wants of the other. The aquarium is a microcosm 
 a world in miniature.* 
 
 * I have read somewhere a beautiful Persian fablo in which a nightin- 
 gale and a rose are represented as being confined in a cage together, and 
 being dependent upon each other for life. The fable is truth symbolized. 
 The idea has now become more practical, but not less beautiful. In the 
 modern aquarium, or drawing-room fish-pond, we see the world in minia- 
 ture. It is a self-regulating, self-subsisting establishment, and is con- 
 structed on the most perfect principles of chemical economy. 
 
 " Before this truth of compensation between animals and plants was 
 discovered, many attempts were made to keep fish in small glass globes. 
 As they soon exhausted the oxygen, and impregnated the water with car- 
 bonic acid, it was necessary to change it daily. Finally, but a few years 
 since, it was discovered that plants evolve oxygen and consume carbonic 
 acid in the water as well as in the air. Starting out with this idea, about 
 the year 1850, a Mr. "Warrington, an Englishman, set about breeding fish 
 and mollusks in tanks by the aid of marine plants. He succeeded admi- 
 rably for a few days, but after a time a change came over his little world. 
 Without apparent reason, the water became suddenly impure, and the fish 
 died. Here was a new agency at work. "With the aid. of a microscope, Mr. 
 Warrington explored his tank for the poison that was evidently latent 
 there. He soon discovered that some of his plants had reached maturity, 
 and, in obedience to the law of nature, had died. The decaying matter 
 was the poison of which he was in search. How was this to be counter- 
 acted? In nature's tanks seas, rivers, and ponds reflected Mr. Warring- 
 ton, plants must die and decay, yet this does not destroy animal life. Wo 
 must see how nature remedies the evil. He hastened to a pond in the 
 vicinity, and examined its bottom with care. He found, as he had antici- 
 pated, an abundance of vegetable matter decayed. He likewise found 
 swarms of water-snails doing duty as scavengers, and devouring the putre- 
 fying substances before they had time to taint the water. Here was the 
 secret ; so beautiful a contrivance that it is said Mr. Warrington burst into 
 tears when it flashed upon him like a revelation. 
 
 " He, however, quickly dried his eyes, gathered a quantity of snails, 
 and threw a handful into his little tank at home. In a single day the 
 water was clear and pure again. The fish throve and gamboled, grew and 
 multiplied ; the plants resumed their bright colors, and the snails not only 
 rollicked in an abundance of decaying branches, but laid a profusion of 
 eggs, on which the fish dined sumptuously every day." 
 
IN POPULAR CHEMISTRY. 77 
 
 .9. What test should be employed before going down in 
 an old ivell or cellar ? 
 
 A lighted candle should be lowered. If that is dimmed or 
 extinguished, it is not safe for one to descend. 
 
 10. What causes the sparkle of wine and the foam of 
 beer? 
 
 The CO 3 formed in the process of fermentation. 
 
 11. What causes the cork to fly out of a catsup bottle ? 
 
 The CO 3 which is produced when the catsup ferments. 
 
 12. What physical principle does the solidification of 
 CO 2 illustrate ? 
 
 That evaporation is a cooling process. A portion of the 
 liquid CO 3 turns to vapor, and thus abstracts so much heat 
 from the remainder as to freeze it. (See Popular Physics, p. 
 255.) 
 
 13. Why does the division in the chimney shown in 
 Fig. 29 produce tivo currents ? 
 
 For a few moments there is an uncertainty a condition of 
 unstable equilibrium. The heated air is tending to rise, and 
 the cold air tending to come in to supply its place. The situ- 
 ation of the candle in the jar determines the length of time 
 before the currents start. If the candle be placed on one side 
 of the jar, they will be established almost instantly. 
 
 14. What causes the unpleasant odor of coal-gas? Is 
 it useful ? 
 
 Impurities which it contains. Olefiant gas has a faint 
 sweetish odor, while carbonic oxide and hydrogen, when pure, 
 are inodorous. The disagreeable smell is due in part to acety- 
 lene (C 2 H 2 ). The unpleasant odor warns us of the presence of 
 coal-gas. 
 
 15. irJiat causes the sparkling often seen in a gas- 
 light? 
 
 Particles of solid taken up mechanically in the process of 
 purification, or otherwise. 
 
78 ANSWERS TO PRACTICAL QUESTIONS 
 
 16. Why does H in burning give out more heat 
 than C? 
 
 1 Ib. of H burned in O emits heat sufficient to melt 315.2 
 Ibs. of ice ; and 12 Ibs. of carbon converted into CO 2 enough to 
 melt 700 Ibs. of ice. (This subject is quite fully treated in 
 Miller's Chemical Physics, page 294, et seq.) The cause is not 
 as yet fully determined, although it is perhaps safe to say that 
 in ordinary combustion the heat depends on the amount of O 
 which enters into combination with the fuel. 
 
 1 7. Wiiy do not stones burn as well as ivood ? 
 
 Because they are already burned, i.e., combined with O. 
 
 18. Why does not hemlock make good coals? 
 
 Because (1) of its lack of C, and (2) its porous structure. 
 
 19. What adaptation of chemical affinities is shown in 
 a light ? 
 
 If O had the same affinity for C that it has for H, they 
 would be consumed at once, with little light. The fact that 
 the H burns first, and thus heats up to the luminous point the 
 particles of C as they float outward to the air, causes the illu- 
 minating power of the hydro-carbons. 
 
 20. Why does snuffing a candle brighten the flame ? 
 
 Because it removes the charred wick, which diminishes the 
 heat of the flame by both conduction and radiation. 
 
 21. Wliy is the flame of a candle red or yellow, and 
 that of a kerosene oil-lamp white ? 
 
 (See Popular Physics, p. 243). 
 
 The heat of a candle-flame is much less than that of kero- 
 sene, and thus the colors characteristic of a lower temperature 
 are produced. 
 
 22. Why does a street gas-light burn blue on a ivindy 
 night ? Is the light then as intense ? The heat ? 
 
 O is mingled with the flame in sufficient quantities to burn 
 the H and C simultaneously. Thereby the heat is increased, 
 
IN POPULAR CHEMISTRY. 79 
 
 but the light diminished. The principle is that of Bunsen's 
 burner. 
 
 23. Why does not the lime burn in a calcium-light ? 
 
 Lime is a burned body ; its symbol is CaO. 
 
 24. Why is a candle-flame tapering ? 
 
 (See Chemistry, p. 77.) 
 
 The currents of air rushing toward the flame from all sides 
 give it the conical form. 
 
 25. Why does a draught of air cause a light to smoke ? 
 
 It lowers the heat of the flame below the point of union 
 between C and O, and thus the C is precipitated. 
 
 26. Wliat makes the coal at the end of a candle-wick ? 
 
 The wick at the edge of the flame comes in contact with 
 the O of the air, and therefore burns. 
 
 27. Which is the hottest part of a flame ? 
 
 Toward the point of the cone, where the gaseous envelopes 
 meet and make a solid flame. 
 
 28. Why does not a candle-wick burn eoccept at the 
 edge of the flame ? 
 
 There is 110 O at the center of the flame. 
 
 29. How does a chimney enable us to burn without 
 smoke highly carboniferous substances like oil ? 
 
 It prevents the heated products of combustion from becom- 
 ing mixed with cold air. These rise, and new air can come in 
 only at the bottom. The stronger the heat in the chimney the 
 greater is this draught. A flame, in which the combustion is 
 imperfect when O is supplied slowly, becomes much brighter 
 when O is supplied fast enough to produce perfect combustion 
 of the H, and also to oxidize all the C without allowing any to 
 pass off as smoke. 
 
 30. How much CO a in 20O Ibs. of chalk ? 
 
80 ANSWERS TO PRACTICAL QUESTIONS 
 
 CO 3 : CaCO 3 : : x : 200 Ibs. 
 44 : 100 : : x : 200 Ibs. 
 100 x = 8,800 Ibs. 
 x = 88 Ibs. (CO S ). 
 
 ?./. What iveight of CO 2 in a ton of marble ? 
 
 CO 2 : CaCO 3 : : x : 2,000 Ibs. 
 44 : 100 : : x : 2,000 Ibs. 
 100 x = 88,000 Ibs. 
 
 x = 880 Ibs. (CO 3 ). 
 
 32. Why does not a cold saucer held over an alcohol 
 flame blacken, as it does over a candle or gas-light ? 
 
 There is less C in alcohol than in tallow or in coal-gas. 
 
 33. How much CO 2 is formed in the combustion of one 
 ton of C? 
 
 C : CO 2 : : 2,000 Ibs. : x. 
 
 12 : 44 : : 2,000 Ibs. : x. 
 12 x = 88,000 Ibs. 
 
 x = 7333.33 + lbs. (CO 3 ). 
 
 34. IWiat weight of Cis there in a ton of CO 2 ? 
 
 C : CO 2 : : x : 2,000 Ibs. 
 
 12 : 44 : : x : 2,000 Ibs. 
 
 44 x = 24,000 Ibs. 
 
 x = 545.45 + Ibs. (C). 
 
 35. Sow much O is consumed in burning a ton of C? 
 
 In any quantity of CO 2 , T \ of the compound is O, and J S T 
 C. If T 3 T = 2,000 Ibs. (COo), then T 8 T = | of 2,000 Ibs. = 5333.33 
 + lbs. (O). 
 
 36. IVliat weight of sodium carbonate (Na 2 CO 3 , 1O 
 H S O, " carbonate of soda") would be required to evolve 12 
 grams of CO 2 ? 
 
 CO 2 : Na 2 CO 3 10ELO : : 12 gm. : x. 
 44 : 286 : : 12 gm. : x. 
 
 44 x = 2,432 gm. 
 
 x = 50.72 gm. (Na 2 C0 3 , 10H S O). 
 
IN POPULAR CHEMISTRY. 81 
 
 37. How much CO 2 will be formed in the combustion 
 of 3O gm. of CO ? 
 
 CO : CO 3 : : 30 gm. : x. 
 
 f 28 : 44 : : 30 gm. : x. 
 
 28 x = 1,320 gm. 
 
 x = 47.14 gm. (CO 2 ). 
 
 38. What tveight of CaCO s would be required to evolve 
 12 grams of CO 2 ? 
 
 CO 2 : CaCO 3 : : 12 : x. 
 44 : 100 : : 12 : x. 
 x = 2?! 3 T grams. 
 
 39. What would be the volume of these 12 grams of 
 CO 2 at 12 C. and 744 mm. ? 
 
 The molecular weight of CO 2 [12 + 2(16)], is 44. Its density 
 is therefore 22. Under standard conditions 1 liter of H weighs 
 .0896 gm. ; therefore 1 liter of CO 2 weighs 22 x. 0896 gm., or 
 1.97 gm. The number of liters that would weigh 12 gm. is 
 
 12 
 
 hence : r7 r^, or 6.09 liters. At 12 C. and 744 mm. this volume 
 1.97 
 
 would be expanded to 
 
 Ar 285 760 _ no 
 V== 273 X ^4 x6m 
 V = 6.494 liters. 
 
 40. Hoiv much C would be necessary to furnish CO 2 
 enough to fill a gas-holder 1O meters high and 4 meters in 
 diameter when the temperature is 25 C., and the barome- 
 ter stands 754 mm. ? 
 
 First find the capacity of the gas-holder. The volume of a 
 cylinder is equal to its length multiplied by the area of its 
 cross action. In this case it is 10 x 3.1416 x(2) a , or 125.664 
 cubic meters. Since in a cubic meter there are 1,000 liters, this 
 volume is 125,664 liters, the temperature being 25 C., and the 
 pressure 754 mm. Reducing this to standard conditions, we 
 
 070 7^4. 
 have V = 125,664 x x 
 
 V = 114,810.5 liters. 
 
82 
 
 ANSWERS TO PRACTICAL QUESTIONS 
 
 Each of these liters of CO 2 weighs 1.97 gm. (see answer 
 to Question 39). Hence the total weight of CO 2 is 114,210.5 x 
 
 1.97 = 224,995 gm. 
 
 CO 3 :C :: 224,995 : x. 
 
 44 : 12 : : 224,995 : x. 
 x = 61.362 T 3 T grams. 
 Or x = 61.362 + , kilograms. 
 
 41. Write in double columns the different properties of 
 carbon dioxide and carbon monoxide ; thus, 
 
 CO 2 is 1, non-inflammable. 
 
 2. Atomic weight 44. 
 
 3. Specific gravity 1.529. 
 
 4. Will not burn. 
 
 5. A negative poison. 
 
 6. Liquefies at 32, and a press- 
 
 ure of 38.5 atmospheres. 
 
 7. Freely soluble in H 2 O. 
 
 8. Forms salts. 
 
 Etc., etc. 
 
 CO is 1, inflammable. 
 
 2. Atomic weight 28. 
 
 3. Specific gravity .967. 
 
 4. Burns with a blue flame. 
 
 5. A direct poison. 
 
 6. Has never been liquefied. 
 
 7. Sparingly soluble in water. 
 
 Etc., etc. 
 
 I IO 1. If chlorine iv at er stands in the sunlight for a 
 time, it ivill only redden a litmus-solution. Why does it 
 not bleach it ? 
 
 Hydrochloric acid is formed, which reddens the litmus. 
 
 2. Why do tinsmiths moisten with HCl, or sal-ammo- 
 niac, the surface of metals to be soldered ? 
 
 It dissolves the coating of oxide, and leaves the surface of 
 the metal free for the action of the solder. 
 
 3. How much HCl can be made from 25 kilos of com- 
 mon salt ? 
 
 NaCl : Cl : : 25 : x. 
 
 58.5 : 35.5 : : 25 : x. 
 
 x 15.17 kilograms. 
 
 4. What weight of NaCl would be required to form 25 
 kilos of HCl? 
 
IN POPULAR CHEMISTRY. 83 
 
 Each molecule of NaCl thus yields one molecule of HC1. 
 HC1 : NaCl : : 25 : x. 
 36.5 : 58.5 : : 25 : x. 
 x = 40 + , kilograms. 
 
 5. HCl of a specific gravity of 1.2 contains about 4O 
 per cent, of the gas. This is very strong commercial acid. 
 What weight could be formed by the HCl gas produced in 
 the reaction named in the preceding problem ? 
 
 25 kilos = .40 x. 
 x = ~= 62.5 kilos. 
 
 4vJ 
 
 f>. What is the difference betiveen sublimation and dis- 
 tillation ? 
 
 A body is said to sublime when it rises as vapor and con- 
 denses in the solid form ; when it condenses as a liquid it is 
 said to distil. 
 
 7. Why do eggs discolor silver spoons ? 
 
 The sulphur of the egg combines with the Ag, forming 
 silver sulphide. 
 
 8. Explain the principle of hair-dyes. 
 
 The two principal chemicals used for dyeing the hair are 
 lead and silver nitrate. The S in the hair combining with the 
 Ag makes silver sulphide, or with the Pb, lead sulphide, either 
 of which stains the hair ; the former colors the skin as well as 
 the hair, while the latter is absorbed through the skin, causing 
 colics and other diseases such as are common among painters. 
 The "golden yellow color" lately in fashion is produced by a 
 solution of arsenic with the hydrosulphate of ammonia. In or- 
 der to dye the lighter tints, it is necessary to bleach the hair 
 with an alkaline solution. See Fireside Science, page 77. 
 
 9. Ts it safe to mix oil of vitriol and water in a glass 
 bottle ? 
 
 The heat produced by the combination of the two will be 
 liable to break the glass. 
 
84 ANSWERS TO PRACTICAL QUESTIONS 
 
 10. What is the color of a sulphuric acid stain on 
 cloth ? How ^vould you remove it ? 
 
 It is generally red, especially on black woolen cloth. The 
 color may be restored by a few drops of a solution of common 
 "soda," or ammonia. 
 
 11. What causes the milky look when oil of vitriol and 
 water are mimed ? 
 
 Pb from the stills in which the acid is condensed, and which 
 is soluble in strong H 3 SO 4 , is precipitated when the acid is di- 
 luted with H 2 O. 
 
 12. What is the chemical relation bettveen animals and 
 plants ? Wliich perform the office of reduction, and which 
 of oxidation ? 
 
 The animal lives on organized materials, taking up O and 
 evolving CO S , and other oxidized products. The plant lives on 
 unorganised materials, CO 2 , HO, NH 3 , and salts, organizing 
 them and evolving O. The function of the animal is oxidation ; 
 that of the plant, reduction. The food of the plant serves 
 merely to increase its bulk ; that of the animal is employed to 
 replace the material worn out by the active operations of life. 
 The animal obtains the energy necessary for its existence from 
 the oxidation of its own body ; the plant obtains the energy 
 necessary for the organization of its food directly from the 
 sun. 
 
 13. How many pounds of S are contained in 1OO Ibs. 
 
 of H 2 SOt ? 
 
 S : H 2 SO 4 : : x : 100 Ibs. 
 
 32 : 98 : : x : 100 Ibs. 
 98 x = 3,200 Ibs. 
 x = 32ff Ibs. (S). 
 
 14. How much O and H 2 O are needed to change a ton 
 of 8O 2 to JT 2 S0 4 ? 
 
 One ton of SO a will make 1 tons of H a SO 4 : of which ? V 
 is H, if is S, and f-f is O. of this O, or 8 T , comes from the 
 
IN POPULAR CHEMISTRY. 85 
 
 air, and % = - 4 \ from the water. (See process of manufacture, 
 Chemistry, p. 106.) Hence, ^ (O) and ^ (R)=& of the acid, 
 was furnished by the water & of lf. tons = ^ ton (H 2 O). 
 
 1 J. Hoiv much O in a Ib. 
 
 f f of any quantity of sulphuric acid are O ; ? V is H ; and 
 If are S. Hence, in 1 Ib. of H 2 SO 3 there are ff Ib. (O). 
 
 16. State the analogy between the compounds of O 
 and S. 
 
 O. 
 
 H 2 O. 
 
 H 2 O 3 (hydrogen dioxide). 
 
 CO.. 
 
 S. 
 
 H 8 S 2 . 
 CS 2 . 
 
 The corresponding compounds possess not only an analo- 
 gous composition, but also similar chemical properties. 
 
 1 48 ! fn the experiment with Na z SO, on page 
 an accurate thermometer will show that in making the so- 
 lution, the temperature of the liquid will fall, and in its 
 solidification, will rise. Explain. 
 
 (See Popular Physics, p. 250.) 
 
 Energy of temperature is absorbed in doing the work of 
 overcoming molecular cohesion ; hence, the thermometer falls 
 while the salt is becoming liquid. In returning to the solid 
 state it gives out this energy again as temperature. 
 
 2. If, in making a solution of Na s SO^, ive use the salt 
 which lias effloresced, and so become anhydrous, the tem- 
 perature will rise instead of falling as before. Explain. 
 
 This is because a solid hydrate is formed before the salt dis- 
 solves in the H 2 O. The same holds true of other anhydrous 
 bodies, as the chlorides of Zn, Fe, and Cu. 
 
 3. IVliy is KNOg, used instead of NaNO^ for making 
 giuipowder ? 
 
 Sodium nitrate is imported from Chili in large quantities, 
 and attempts have been made to use it for making gunpowder,* 
 
 * Gunpowder is an intimate mechanical mixture of about 1 part niter, 
 1 part sulphur, and 3 parts charcoal. These proportions, however, vary 
 
86 ANSWERS TO PRACTICAL QUESTIONS 
 
 but its tendency to attract moisture has frustrated the plan. It 
 is now extensively used as a fertilizer, and is said to be the 
 cheapest form in which N can be furnished the soil. 
 
 4. Why is a potassium salt preferable to a sodium one 
 in glass-making ? 
 
 Sodium salts give a greenish tint to the glass. 
 
 5. What is the glassy slag so plentiful about a fur- 
 nace ? * 
 
 A silicate of lime or some other base contained in the ore. 
 
 Ordinary Slag from Blast Furnace (Bloxam). 
 
 Silica 43.07 
 
 Alumina 14.85 
 
 Lime 28.92 
 
 Magnesia 5.87 
 
 Oxide of iron 2.53 
 
 Oxide of manganese 1.37 
 
 Potash. 1.84 
 
 Sulphide of calcium 1.90 
 
 Phosphoric acid trace 
 
 100.35 
 
 somewhat in different countries, as well as in different sorts of powder. 
 More charcoal adds to its power, but also causes it to attract moisture from 
 the air, which of course injures its quality. For blasting rocks, where a 
 sustained force, rather than an instantaneous one, is required, the powder 
 contains more sulphur, and is even then often mixed with sawdust to re- 
 tard the explosion. The niter, sulphur, and charcoal, having been ground 
 and sifted separately, are thoroughly mixed, and then made into a thick 
 paste with water. This is ground for some hours under edge-stones, after 
 which it is subjected to immense pressure between gun-metal plates, form- 
 ing what is known as press-cake. These cakes are then submitted to the 
 action of toothed rollers, whereby the granulation of the powder is effected. 
 The grains thus formed are sorted into different sizes by means of a series 
 of sieves, and thoroughly dried at a steam heat. The last operation, that 
 of polishing, is accomplished in revolving barrels, after which the powder 
 is ready for market. The heavier the powder, the greater is its explosive 
 power. Good powder should resist pressure between the fingers, giving no 
 dust when rubbed, and have a slightly glossy aspect. YOTJMANS. 
 
 * The slag is commonly employed for road-making in the neighborhood 
 of the iron-works. Some attempts have been made to turn the slag to ac- 
 count by employing it as a manure for soils deficient in potash, of which 
 
IN POPULAR CHEMISTRY. 87 
 
 6. State the formula? of niter, saleratus, carbonate and 
 bicarbonate of soda, plaster, pearlash, saltpeter, plaster of 
 Paris, gypsum, carbonate and bicarbonate of potash, sal- 
 soda, and soda. 
 
 Niter, saltpeter 
 
 Saleratus, pearlash ........................................ HKCO 3 . 
 
 Carbonate of soda, sal-soda .............................. Na 2 CO 3 . 
 
 Bicarbonate of soda, " soda " ............................ H3STaCO 3 . 
 
 Plaster, gypsum ........................................... CaSO,2H 2 O. 
 
 Plaster of Paris ........................................... CaSO 4 . 
 
 7. Explain hoiv ammonium carbonate is formed in the 
 process of maMng coal-gas. 
 
 Nitrogen exists in small quantities in coal, and when that 
 is distilled at a high temperature, the elements in their nascent 
 state combine to form this compound. 
 
 8. Upon what fact depends the formation of stalactites ? 
 
 Water containing carbonic acid in solution will dissolve car- 
 bonate of lime freely, but when, on exposure to the air, the 
 gas escapes, the carbonate is deposited. 
 
 9. iniy is HF kept in gutta-percha bottles ? 
 
 Because it will dissolve silica, and so destroy a glass bottle. 
 
 10. Explain the use of borax in washing. 
 
 It softens "hard" water by uniting with the soluble salts 
 of lime or magnesia, and making insoluble ones which settle 
 and form a thin sediment in the bottom of pitchers in which it 
 is placed. 
 
 11. How are petrifactions formed ? 
 
 Certain springs contain large quantities of some alkaline 
 carbonate ; their waters, therefore, dissolve silica abundantly. 
 If we place a bit of wood in them, as fast as it decays, parti- 
 
 it will be seen that the above slag contains nearly g^th of its weight, in a 
 form which would be easily rendered available for plants by the combined 
 action of air and moisture. When the slag is run into water, or blown 
 into a frothy condition by the blast, it resembles pumice-stone, and is easily 
 ground to a powder fit for applying to the soil. 
 
88 ANSWERS TO PRACTICAL QUESTIONS 
 
 cles of silica will take its place atom by atom and thus pet- 
 rify the wood. The wood has not been changed to stone, but 
 has been replaced by stone. 
 
 12. In what part of the body, and in ivhat forms, is 
 pJiosphorus found ? 
 
 As a phosphate it is tho principal earthy constituent of the 
 bones. It is also a never-failing ingredient of the brain and 
 nervous system. The susceptibility of phosphorus to oxidation 
 especially adapts it to the rapid changes incident to the struct- 
 ure and offices of the brain.* 
 
 * Phosphorus is an element which can imperceptibly and quickly pass 
 from a condition of great chemical activity to one of equal chemical inert- 
 ness. In virtue of this character, it " may follow the blood in its changes, 
 may oxidize in the one great set of capillaries, and be indifferent to oxygen 
 in the other; may occur in the brain, in the vitreous form, changing as 
 quickly as the intellect or imagination demands, and literally naming that 
 thoughts may breathe and words may burn ; and may be present in the 
 bones in its amorphous form, content like an impassive caryatid, to sustain 
 upon its unwearied shoulders the mere dead weight of stones of flesh. And 
 what is here said of the brain as contrasted with the bones, will apply with 
 equal or similar force to many other organs of the body. All throughout 
 the living system, we may believe that phosphorus is found at the centers 
 of vital action in the active condition, and at its outlying points in the 
 passive condition. In the one case it 13 like the soldier with his loaded 
 musket pressed to his shoulder and his fmger on the trigger, almost antici- 
 pating the command to fire ; in the other it is like the same soldier with 
 his unloaded weapon at his side standing at ease." 
 
 " Further, phosphorus forms with oxygen a powerful acid, capable even 
 of abstracting water from sulphuric acid, and yet perfectly unirritating 
 to the organic textures. Taking up varying quantities of water, phosphoric 
 acid assumes no fewer than three distinct forms, which will unite with 
 one, two, or three atoms of alkali respectively, giving an acid, neutral, or 
 alkaline reaction. Thus it is available for the most varied uses in the 
 body. A child is beginning to walk, and tho bones of its limbs must be 
 strengthened and hardened ; phosphoric acid, accordingly, carries with it 
 three units of lime to them, and renders them solid and iirir. But the 
 bones of its skull must remain comparatively soft and yielding, for it has 
 many a fall, and the more elastic these bones are, the less will it suffer 
 when its head strikes a hard object ; so that in them we may suppose the 
 phosphoric acid to retain biit two units of lime, and to form a softer, less 
 consistent solid. And the cartilages of the ribs must be still more supple 
 and elastic, so that in them the phosphoric acid may be sxipposed to be 
 
IN POPULAR CHEMISTRY. Si) 
 
 13. Why are matches poisonous? What is the anti- 
 dote ? 
 
 Because of the phosphorus in the match. Turpentine has 
 been proposed as a remedy, but is not known to be reliable. 
 
 14. Will the burning phosphorus ignite the wood of the 
 match ? 
 
 It does not give off enough heat in its oxidation to raise the 
 temperature of the wood to the igniting point. Some substance 
 of low kindling point, such as sulphur, or which contains a 
 large amount of O, such as KC1O ;J , is added to produce violent 
 oxidation and kindle the wood. 
 
 15. What principle is illustrated in the ignition of a 
 match by friction ? 
 
 The conversion of motion into heat. 
 
 l(t. How much H Z O would be required to dissolve a 
 pound of KNO Z ? 
 
 3i Ibs. of cold water, or i Ib. of hot water. 
 
 17. What causes the bad odor after the discharge of a 
 gun ? 
 
 The potassium sulphide gradually gives up its S to form 
 
 combined with, but one unit of base. On the other hand, its teeth must 
 be harder than its hardest bones, and a new demaiid is made on the lirae- 
 phosphates to associate themselves with other lime-salts (especially fluoride 
 of calcium), to form the cutting edges and grinding faces of the incisors 
 and molars. All the while, also, the blood must be kept alkaline, that oxi- 
 dation of the tissues may be promoted, and albumen retained in solution ; 
 and yet it must not be too alkaline, or tissues and albumen will both be 
 destroyed, and the carbonic acid developed at the systemic capillaries 
 will not be exchanged for oxygen when the blood is exposed to that gas 
 at the lungs. So phosphoric acid provides a salt containing two units 
 of soda and one of water, which is sufficiently alkaline to promote oxida- 
 tion, dissolve albumen, and absorb carbonic acid, and yet holds the latter 
 so loosely, that it instantly exchanges it for oxygen when it encounters 
 that gas in the piilmonary capillaries. Again, the flesh juice must be kept 
 acid (perhaps in opposition to the alkaline blood, as affecting the trans- 
 mission of the electric currents which traverse the tissues), and phosphoric 
 acid provides a salt, containing two units of water and one of potash, 
 which secures the requisite acidity. 11 DR. G. WILSON, Edinburgh Essays, 1856. 
 
90 ANSWERS TO PRACTICAL QUESTIONS 
 
 18. Write in parallel columns the properties of com- 
 mon and of red phosphorus. 
 
 Common phosphorus. 
 
 1. Specific gravity 1.83. 
 
 2. Burns at 111. 
 
 3. Odor of garlic. 
 
 4. Soluble in CS 2 . 
 
 5. Colorless, or straw-yellow. 
 
 6. A deadly poison. 
 
 Amorphous phosphorus. 
 
 1. Specific gravity 2.14. 
 
 2. Burns at 500. 
 
 3. Odorless. 
 
 4. Insoluble in CS 3 . 
 
 5. Brownish red. 
 
 6. Harmless. 
 
 19. IVTiat causes the difference between fine and coarse 
 salt ? 
 
 (See Chemistry, p. 132.) 
 
 The rapidity of evaporation in the process of manufacture. 
 
 20. WJiy do the figures in a glass paper-weight look 
 larger when seen from the top than from the bottom ? 
 
 The form of the glass acts like a convex lens to magnify 
 the apparent size of the figures. 
 
 21. What is the difference between water-slacked and 
 air-slacked lime ? 
 
 The former is simply calcium hydrate, CaO, H 2 O, while the 
 latter has absorbed both H 2 O and CO 3 from the air. 
 
 22. Why do oyster-shells on the grate of a coal-stove 
 prevent the formation of clinkers ? 
 
 The lime of the shells acts as a flux with the iron in the 
 coal, thus dissolving the clinkers, if any form. 
 
 23. How is lime-water m,adefrom oyster-shells ? 
 
 The shells are burned, driving off the CO 2 combined with 
 the CaO in the CaCO 3 , and the lime thus formed is slightly 
 soluble in water. 
 
 24. IVliy do newly plastered walls remain damp so 
 long? 
 
 The plaster or mortar in drying gives off the water the 
 lime took up in slacking. 
 
AY POPULAR CHEMISTRY. 91 
 
 25. Will lime lose its beneficial effect upon a soil after 
 frequent applications ? 
 
 Lime acts in various ways to improve the fertility of a soil. 
 It corrects its acidity, aids in the decomposition of the rocky 
 constituents, hastens the decay of the humus, and also makes 
 the soil more -porous. It does not, however, benefit the grow- 
 ing plant directly, but works up other materials in the soil. It 
 therefore loses its effect after a time. The Belgian farmers 
 have a proverb : 
 
 " Much, lime and no manure, 
 Make farm and farmer poorer." 
 
 26. What causes plaster of Paris to harden again after 
 being moistened ? 
 
 (Seo Chemistry, p. 141.) 
 
 It recombines with water, which was driven off in the 
 process of its manufacture. 
 
 27 What is the difference between sulphate and sul- 
 phite of lime? 
 
 The former is a compound of sulphuric acid ; the latter of 
 sulphurous acid. 
 
 28. What two classes of rays are especially abundant 
 in the magnesium light ? 
 
 (See Popular Physics, p. 243.) 
 
 The actinic and the luminous rays. The former are less than 
 ^u^Tnr of an mcn m length, and produce chemical change. 
 
 29. What rare metals would become useful in the arts 
 if the process of manufacture were cheapened ? 
 
 Magnesium, aluminum, sodium, etc. 
 
 30. Why is lime placed in the bottom of a leach-tub ? 
 
 The potash of the ashes is generally in the form of a car- 
 bonate, the acid neutralizing in part the strength of the alkali. 
 The lime combines with the CO 2 . 
 
 31. Is saleratus a salt of IL or of Na? 
 
 It should be a carbonate of K, but, on account of its 
 cheapness, the corresponding salt of Na is often sold instead. 
 
92 ANSWERS TO PRACTICAL QUESTIONS 
 
 32. Why iv ill Na burst into a Maze wJien thrown on 
 hot water, or put on wetted blotting paper ? 
 
 The oxidation of the JSTa produces heat, part of which is 
 absorbed by the cold water, over which the pellet moves rap- 
 idly about, so that the kindling point of H i3 not quite reached. 
 If the water be previously heated, or if the Na is prevented 
 from moving abcut, by resting it on wetted blotting paper, the 
 H from the H 2 O is quickly raised to its kindling point. It 
 burns by taking O from the air, and its flame is colored yellow 
 by volatilizing some of the Na while the rest is taking O from 
 the water, and its hydrate is passing into solution. 
 
 33. Why are certain Kinds of brick white ? 
 
 They contain no iron, this being the substance which by its 
 oxidation gives the color to common brick. 
 
 34. Illustrate the power of chemical affinity. 
 
 Half the crust of the earth is made up of oxides, whose 
 constituents are held together by chemical affinity. To separate 
 the O from these elements, with which it is united, is exceed- 
 ingly difficult ; so much so that the attempt is but rarely ever 
 made. 
 
 35. Why does not a candle lowered into a jar of Cl go 
 on burning indefinitely ? 
 
 The Cl around it becomes mixed with HC1 fumes, which 
 stop the action. 
 
 181 1. Pb is softer than Fe ; whij is it not wore 
 malleable ? 
 
 The facility with which a mass of metal can be hammered 
 or rolled into a thin sheet without being torn, must depend 
 partly upon its softness, and partly upon its tenacity. If it 
 depended upon softness alone, lead should be the most malleable 
 of ordinary metals ; but, although it is easy to hammer a 
 mass of lead into a, flat plate, or to squeeze it between rollers, 
 any attempt to reduce it to an extremely thin sheet fails, from 
 its want of tenacity, which causes it to be worn into holes by 
 percussion or friction. On the other hand, if malleability were 
 
IN POPULAR CHEMISTRY. 
 
 93 
 
 entirely regulated by tenacity, iron would occupy the first place, 
 whereas, on account of its hardness, it is the least malleable of 
 metals in ordinary use ; while gold, occupying an intermediate 
 position with respect to tenacity, is the most malleable, which 
 appears surprising to those who are only acquainted with gold 
 in its ordinary forms of coin and ornament, in which it is 
 hardened and rendered much less malleable by the presence of 
 copper and silver. 
 
 I. Relative Malleability of the Metals. 
 
 1. Gold. 4. Tin. 
 
 2. Silver. 5. Platinum. 
 
 3. Copper. 6. Lead. 
 
 TL. Relative Tenacity of the Metale. 
 
 7. Zinc. 
 
 8. Iron. 
 
 Tin 
 
 3.3 
 
 Platinum 
 
 l(i 
 
 Zinc 
 
 2 
 
 Copper. 
 
 18 
 
 Palladium 
 
 114 
 
 Iron 
 
 ..' 27 1 
 
 Gold... 
 
 ..12 
 
 Steel.... 
 
 .. 42 
 
 1. Gold. 
 
 2. Silver. 
 
 3. Platinum. 
 
 4. Iron. 
 
 III. Relative Ductility of the Metal*. 
 5. Copper. 
 
 6. Palladium. 
 
 7. Aluminum. 
 
 8. Zinc. 
 
 0. Tin. 
 
 10. Lead. 
 
 BLOXAM. 
 
 2. WJiat is the cause of the chanf/iitfs color often seen in 
 thf scum on standing ivater? 
 
 (See " Interference of Light, 1 ' Popular Physics, p. 220.) 
 The thin pellicles of iron-rust on standing H 8 O produce a 
 beautiful iridescent appearance, the color changing with the 
 thickness of the oxide. A soap-bubble exhibits in the same way 
 a play of variegated colors according to the thickness of the 
 film in different parts. 
 
 3. How can the spectra of the metals be obtained ? 
 
 (See Astronomy, p. 285.) 
 
 By looking through a prism at a flame containing minute 
 portions of the volatilized metal, and no solid particles of C. 
 
 4. Ought cannon, car-axles, etc., to be nsed until they 
 break or wear out ? 
 
94 ANSWERS TO PRACTICAL QUESTIONS 
 
 Cannon are condemned and recast after being fired a cer- 
 tain number of times, even though they show no flaw, as the 
 jarring to which they are exposed causes the iron to take on a 
 crystalline form, and become less fibrous and tough. A cast- 
 iron gun of 10-inch bore or less, ought to stand 1,000 rounds ; 
 larger calibers, a smaller number. 
 
 5. IVliy is " chilled iron" used for safes ? 
 
 The iron being cooled so instantaneously, the crystals are 
 exceedingly small, and the metal is correspondingly harder than 
 when cast in the ordinary way. 
 
 6. Docs a blacksmith plunge his ivork into water 
 merely to cool it? 
 
 The metal is harder when cooled quickly, and therefore re- 
 sists wear longer. 
 
 7. What causes the white coating made ^vhen we spill 
 water on zinc ? 
 
 The oxide of zinc which is formed on the surface of the 
 metal through the favoring influence of the water. 
 
 8. Is it well to scald pickles, make sweetmeats, or fry 
 cakes in a brass kettle ? 
 
 (See Chemistry, p. 161.) 
 
 9. WJiat danger is there in the use of lead pipes ? Is a 
 lining of Zn or Sit a protection ? 
 
 (See Chemistry, p. 162, and Fireside Science, p. 149.) 
 Zinc and tin are corroded by oxygen, though less readily 
 than Pb, and, while their salts are poisonous, the lead is soon 
 laid bare, and this also oxidizes. 
 
 10. Is ivater which It as stood in a metal-lined ice- 
 pitcher healthful ? 
 
 (See Chemistry, p. 159.) 
 
 The dissimilar metals fastened with solder, which corrodes 
 
 in the presence of water, develop a voltaic current which, 
 
 hastens the oxidation. The salts thus formed are very dan 
 gerous. 
 
IN POPULAR CHEMISTRY. 95 
 
 11. If yon ask for " cobalt" at a drug-store, tvhat will 
 you get? If for "arsenic"? 
 
 Impure metallic arsenic is sold as "cobalt," while arsenious 
 anhydride is called "arsenic." 
 
 12. What two elements are fluid at ordinary tempera- 
 tures ? 
 
 Bromine and mercury. 
 
 13. Should we touch a gold ring to mercury ? 
 
 The mercury will form with the gold an amalgam. 
 
 14. Wliy does silver blacken if handled ? 
 
 The perspiration of the body contains S, which combining 
 with the metal forms silver sulphide, which is black. 
 
 15. IVIiy does silver tarnish rapidly where coal is used 
 for fires ? 
 
 S, which is present in coal, forms a silver sulphide. 
 
 16. Why is a solution of coin blue ? 
 
 From the Cu which is contained in silver coin forming Ou 
 (NO 3 ) 2 , which is blue. 
 
 17. MTIiy will a solution of silver nitrate curdle brine ? 
 
 A white, curdy precipitate of silver chloride is formed. 
 
 18. Wliy does writing with indelible ink turn black 
 when exposed to the sun, or to a hot iron ? 
 
 By the decomposition of the silver salt contained in the 
 ink, and consequent production of Ag 2 O, which stains organic 
 matter black. 
 
 19. What alloys resemble gold ? 
 
 Oroide, aluminum-bronze, etc. 
 
 2O. WJiy does a fish-hook " rust out" the line to which 
 it is fastened ? 
 
 Ferric oxide and ferric hydrate act as conveyers of O, ab- 
 sorbing it from the air and giving it up to organic bodies with 
 which they are in contact. 
 

 96 ANSWERS TO PRACTICAL QUESTIONS 
 
 21. Why do the nails in clap-boards loosen ? 
 
 See Question 20. 
 
 22. Show that the earth's crust is mainly composed of 
 
 burnt metals. 
 
 (See Cooke's Religion and Chemistry.) 
 
 It consists largely of potassium, magnesium, calcium, alu- 
 minum, sodium, etc., in combination with O. These compounds 
 are the products of combustion. 
 
 The elements O, Si, Al, Mg, Ca, K, Na, Fe, C, S, H, Cl, 
 and N 13 in all probably make up T 9 ^ of the earth's crust. 
 
 23. What kind of iron is used for a magnet ? For a 
 magnetic needle ? 
 
 Steel for a permanent magnet, and therefore for a magnetic 
 needle ; pure soft iron for an electro-magnet. 
 
 24. Why does a "tin" pail so quickly rust out when 
 once the tin is worn through ? 
 
 These pails are made of sheet iron, which is covered with a 
 coating of tin, which causes the popular name for them. If 
 this is scratched through, the iron and tin in contact are ex- 
 posed to the water ; voltaic action is started, and the iron rap- 
 idly rusts. 
 
 25. Wlty is the zinc oacide found in Neiv Jersey red 9 
 when zinc rust is white ? 
 
 The oxide in New Jersey is colored by compounds of iron 
 and manganese. 
 
 26. Should we filter a solution of permanganate of 
 potash through paper ? 
 
 (See Chemistry, p. 157, note.) 
 No. The salt will give up O and corrode the filter. 
 
 27 Why is woody cordage, etc., sometimes soaked in a 
 solution of corrosive sublimate ? 
 
 This salt possesses strong antiseptic properties. 
 
 28. Why does the ivhite paint around a sink turn 
 black? 
 
IN POPULAR CHEMISTRY. 97 
 
 H 2 S is set free, which, acting on the paint, forms lead sul- 
 phide, which is black. 
 
 29. Why is aluminum, rather than platinum, used for 
 making the smallest weights ? 
 
 Because of its low specific gravity as compared with that 
 of platinum. 
 
 30. How would you detect the presence of iron particles 
 in Mack sand ? 
 
 By a magnet. 
 
 31. Which metals can be welded ? 
 
 Iron and platinum, most easily ; others also by using a pow- 
 erful electric current to heat the ends of the pieces of metal. 
 
 32. When the glassy slag from a blast-furnace has a 
 dark color, ^vhat does it show ? 
 
 It might be anticipated that the appearance of the slag 
 would convey to the experienced eye some useful information 
 with respect to the character of the ore and the general prog- 
 ress of the smelting operation. A good slag is liquid, nearly 
 transparent, of a light-gray color, and has a fracture somewhat 
 resembling that of limestone. A dark slag shows that much 
 of the oxide of iron is escaping unreduced. Streaks of blue 
 are commonly found when ores containing sulphur are being 
 smelted, possibly from the presence of a substance similar to 
 ultramarine, the constituents of which are all present in the 
 slag. Again, the slags obtained in smelting ores containing 
 titanium generally present a peculiar blistered appearance. 
 BLOXAM. 
 
 33. In welding iron the surfaces to be joined are some- 
 times sprinkled with sand. Explain. 
 
 The silica acts as a flux with the oxide upon the surface, 
 and lays bare the metal for welding. 
 
 34. Wliat is the difference between an alloy and an 
 amalgam ? 
 
 An amalgam is composed of mercury and some other 
 metal. An alloy consists of any metals whatever. 
 
98 ANSWERS TO PRACTICAL QUESTIONS 
 
 35. Steel articles (ire blued to protect from rusting, by 
 heating in a sand-bath. Explain. 
 
 A thin coating of oxide is formed on the surface of the 
 metal. 
 
 36. Give the formulas for copperas and white lead. 
 
 1. FeSO 4 = FeO,SO 3 . 
 
 2. PbCO 3 = PbO,C0 3 . 
 
 37. Why is Hg used for filling thermometers ? 
 
 Because it is fluid at all ordinary temperatures. 
 
 38. What oxides are formed by the combustion of Na 9 
 K, Zn, 8, Fe, Pb, Cti, P, etc. ? Which are bases ? Anhy- 
 drides ? Give the common name of each. 
 
 (1.) Na 2 O is formed when ISTa oxidizes in dry air, or oxy- 
 gen at a low temperature. This takes up water with great 
 avidity, forming HNaO (NaHO), sodium hydroxide. Na 2 O 2 is 
 made when Na is heated to 200 C. HNaO is. the caustic soda 
 of commerce, and is an alkaline base. 
 
 (2.) K in a similar manner, depending upon the tempera- 
 ture, forms K 2 O, K 2 O 2 , and K 2 O 4 . The first, with water, 
 forms the ordinary caustic potash, HKO, of commerce. It is 
 an alkaline base. 
 
 (3.) ZnO is the only known oxide of zinc. It forms salts. 
 
 (4.) Seven compounds of S and O are known, but only two 
 are of interest the familiar anhydrides, SO 2 and SO 3 . 
 
 (5.) The oxides of iron are four in number : (1) the mon- 
 oxide, or ferrous oxide, FeO, from which the green ferrous salts 
 are derived ; (2) the sesquioxide, or ferric oxide, Fe 2 O 3 , yield- 
 ing the yellow ferric salts; (3) the magnetic or black oxide, 
 Fe 3 O 4 , which does not form any definite salts ; (4) ferric acid, 
 H 2 FeO 4 , a weak acid, forming colored salts with potassium. 
 
 (6.) Pb forms two oxides, the monoxide and the dioxide. 
 The former is the well-known litharge, which is the base of 
 the lead salts. 
 
 (7.) Cu has two oxides the cuprous (Cu a O) and cupric 
 (CuO), both of which form salts, thus giving rise to two series, 
 
IN POPULAR CHEMISTRY. 99 
 
 the cuprous and the cupric salts. The two oxides are com- 
 monly known as the red and the black. 
 
 (8.) Phosphorus forms two oxides, phosphorous anhydride 
 (P 2 O 3 ) and phosphoric anhydride (P 2 O 5 ). 
 
 39. Is charcoal lighter than H 2 O ? 
 
 Charcoal appears at first sight to be lighter than water, as 
 a piece of it floats on the surface of this liquid ; this is, how- 
 ever, due to the porous nature of the charcoal, for if it be 
 finely powdered it sinks to the bottom of the water. ROSCOE. 
 
 40. Name the.vitriols. 
 
 The compounds of sulphuric acid, commonly called "the 
 vitriols," are as follows: 
 
 1. Sulphate of iron, Green vitriol. 
 
 2. Sulphate of copper, Blue vitriol. 
 
 3. Sulphate of zinc, White vitriol. 
 
 41. Is My univalent or bivalent ? Zn ? 
 
 Mg belongs to the zinc class of metals which comprises 
 magnesium, zinc, cadmium, and indium. These are all bivalent. 
 
 42. Name some dibasic acid. 
 
 Sulphuric acid. 
 
 43. Name a neutral salt. An acid salt. 
 
 Sodium sulphate is neutral (Na 2 SO 4 ). Hydro-sodium sul- 
 phate is acid (HNaSOJ. 
 
 44. Calculate the percentage of water contained in 
 crystallized copper sulphate. Sodium sulphate. Calcium 
 sulphate. Alum. 
 
 (1.) CuSO 4 , 5H 3 O = 249.5. 
 5H 2 = 90. 
 
 Hence, -$% = .36 = 36 % of copper sulphate is water. 
 
 (2.) Na 2 SO 4 , 10H 2 O = 322. 
 10H 2 O = 180. 
 
 Hence, iff = .55 = 55 % of sodium sulphate is water, 
 
100 ANSWERS TO PRACTICAL QUESTIONS 
 
 (3.) CaSO 4 , 2H 2 O = 172, 
 
 '2H 2 O = 36. 
 Hence, -^ = .20 = 20 % of gypsum is water. 
 
 (4.) A1 2 K 2 , 4SO 4 +24H 2 O = 949. 
 24H 2 O = 432. 
 Hence, $ff = .45 45 % of potash alum is water. 
 
 45. What is the test for Ay ? Ca ? 
 
 Ag can be easily detected when in solution by the precipi- 
 tation of the white, curdy chloride, insoluble in H 2 O and 
 HNO 3 , and soluble in H 3 N : the metal can be obtained in 
 malleable globules before the blowpipe, and is reduced from its 
 solutions by Fe, Cu, P, and Hg. Ag is estimated quantita- 
 tively either as the chloride or as the metal. 
 
 Copper may be tested (1) by the black insoluble sulphide ; 
 (2) by the blue hydrate turning black on heating ; (3) by the 
 deep-blue coloration with ammonia ; (4) by the deposition of 
 red metallic copper upon a bright surface of iron placed in the 
 solution. 
 
 40. What weight of crystallized "tin salts" (SnCl 2 , 
 2H 2 O) can be prepared from one ton of metallic tin ? 
 
 Sn : SnCl 2 , 2H 3 O : : 2,000 Ibs. : x. 
 118 : 225 :: 2,000 Ibs. : x. 
 
 118 x = 450,000 Ibs. 
 
 x = 3813.56 Ibs. (SnCU, 2H 2 O). 
 
 47. 1OO parts by weight of silver yield 132.87 parts of 
 silver chloride. Given the atomic iveiyht of chlorine (35.4], 
 required that of silver. 
 
 32.87 : 100 : : 35.4 : x. 
 
 48. What is the composition of slacked lime ? 
 
 (See Chemistry, p. 139.) 
 OaO,H 2 0. 
 
 49. How is ferrous sulphate obtained? How many 
 tons of crystals can be obtained by the slow oxidation of 
 
IN POPULAR CHEMISTRY. 
 
 101 
 
 23O tons of iron pyrites containing 37.5 per cent, of 
 
 sulphur ? 
 
 (See Cfiemistry, p. 158.) 
 
 3?i % of 230 = 86.25 tons, the weight of S contained in the 
 pyrites. 
 
 S : FeSO 4 , 7H 2 O : : 86.25 : x. 
 
 32: 278 :: 86.25 : x. 
 
 x = 749.296 tons of FeSO 4 , 7H 2 O. 
 
 50. Required 5OO tons of soda crystals; what willbe 
 the weight of salt and pure sulphuric acid needed ? 
 
 Find (1) how much Na there is in 500 tons of "soda," and 
 (2) how much NaCl would be needed to furnish that amount of 
 the metal in case all were utilized. 
 
 (1.) Na 2 : Na 2 CO 3 , 10H 2 O : : x : 500 tons. 
 46 : 286 : : x : 500 tons. 
 
 286 x 23,000 tons. 
 
 x = 80.42 - tons (Na). 
 
 (2.) Iff of any amount of NaCl is Na ; hence, to furnish 
 80.42 tons of Na would require ff|x80.42 tons = 204.546 tons 
 (Nad). 
 
 (3.) By comparing the atomic weights of the substances, it 
 will be seen that for 46 parts of Na there must be 98 of pure 
 H 2 SO 4 . ft x 204.546 tons = 435.771 tons (H 2 SO 4 ). 
 
 51. Describe the uses of lime in agriculture. 
 
 Lime acts in various ways to improve the fertility of a soil. 
 It corrects its acidity, aids in the decomposition of the rocky 
 constituents, hastens the decay of the humus, and also makes 
 the soil more porous. It does not, however, benefit the grow- 
 ing plant directly, but works up other materials in the soil. It 
 therefore loses its effect after a time. 
 
 52. Hoiv many tons of oil of vitriol, containing 7O per 
 cent, of pure acid (Jf 2 O 4 ), can be prepared from 25O tons 
 of iron pyrites, containing 42 per cent, of sulphur ? 
 
 (1.) (See Question 49.) 250 tons x. 42 = 105 tons (S). 
 (2.) S : H 3 SO 4 : : 105 tons : x. 
 32 : 98 : : 105 tons : x. 
 32 x = 10,290 tons. 
 
 x = 321.56 tons (H 8 SO 4 ). 
 
102 ANSWERS TO PRACTICAL QUESTIONS 
 
 (3.) If 321.56 tons (H 2 SO 4 ) is 70 % of the given oil of vit- 
 riol, the entire amount would be 321.56 tons x -^ = 459.28 tons 
 (oil of vitriol). 
 
 247 1. Hoiv would you prove the presence of tannin 
 in tea ? 
 
 By adding a few drops of a solution of ferrous sulphate. 
 This would form a dark precipitate of iron tannate. 
 
 2. How would you test for Fe in a solution ? 
 
 (See MUler's Inorganic Chemistry, p. 625.) 
 
 A solution of nutgalls will give a bluish-black, inky precipi- 
 tate. The ferrous- or proto-salts are distinguished by their light 
 green color, and by their solutions giving (1) a white precipi- 
 tate, with caustic alkalies ; (2) a light blue precipitate, with po- 
 tassium ferrocyanide, which rapidly becomes dark; while the 
 ferric- or per-salts are yellow-colored, and their solutions yield 
 (1) a deep reddish-brown precipitate, with the caustic alkalies ; 
 and (2) a deep-blue precipitate (Prussian blue), with potassium 
 ferrocyanide. 
 
 3. Why can we settle coffee with an egg ? 
 
 The albumen of the egg coagulates by heat, and, entan- 
 gling the particles of coffee, mechanically carries them to the 
 bottom. 
 
 4. How would you show the presence of starch in a 
 potato ? 
 
 A solution of iodine will form the blue iodide of starch. 
 
 5. IVJiy is starch stored in the seed of a plant? 
 
 For the growth of the young plant. 
 
 6*. Why are unbleached cotton goods dark-colored ? 
 
 Because of the dirt gathered in the process of manufacture. 
 The cotton balls are snowy white. 
 
 7. Why do beans, rice, etc. 9 swell when cooked ? 
 
 On account of the bursting of the starch granules. 
 
 8, Wliy does decaying wood darken ? 
 
IN POPULAR CHEMISTRY. 103 
 
 On account of the formation of humus, which contains car- 
 bon in excess. 
 
 9. How would you show that C exists in sugar ? 
 
 By heating it until the H and O are all driven off. A mass 
 of porous charcoal remains on the plate. 
 
 1O. Whyr do fruits lose their sweetness when over-ripe ? 
 
 (See Miller's Organic Chemistry, p. 875.) 
 
 The vegetable acid contained in the fruit when green, oxi- 
 dizes as the ripening process continues, O being absorbed, and 
 CO 3 evolved. If this continues too long, the sugar itself be- 
 comes oxidized. 
 
 11. Why does maple-sap lose its sweetness when the leaf 
 starts ? 
 
 The sugar of the sap is applied to the wants of the grow- 
 ing tree. 
 
 12. Should yeast-cakes be allowed to freeze? 
 
 A cold of 32 will kill the ferment. 
 
 13. Why will ivine sour if the bottle be not well corked ? 
 
 The presence of air will cause the continuation of the oxi- 
 dizing process into the second or acetic stage. 
 
 14. W7iy can vinegar be made from sweetened water 
 and brown paper ? 
 
 The paper acts as a ferment, while the sugar or molasses is 
 oxidized into alcohol, and thence into acetic acid. 
 
 15. Why should the vinegar-barrel be kept in a warm 
 place ? 
 
 Fermentation takes place to the best advantage at a special 
 temperature, about 70 F. 
 
 16. Why does "scalding" check the "working" of 
 preserves ? 
 
 The ferment which causes the fermentation is killed by the 
 heat. 
 
104 ANSWERS TO PRACTICAL QUESTION'S 
 
 1 7. Is the oxalic acid in the pie-plant poisonous ? 
 
 It is neutralized by the alkaline base, with which it is com- 
 bined in the plant. 
 
 18. How may ink-stains be removed ? 
 
 By a solution of oxalic acid, forming an iron oxalate which 
 is soluble in water, and hence may be washed out. 
 
 W. Wliy is leather black on only one side ? 
 
 The solution of copperas, which blackens the leather, is ap- 
 plied on only one side. 
 
 20. JfJiy do drops of tea stain a knife-blade ? 
 
 The tannic acid of the tea combines with the iron, forming 
 an iron tannate.* 
 
 21. Why will not coffee stain it in the same way ? 
 
 (See Miller's Organic Chemistry, p. 549.) 
 
 The modification of tannin contained in coffee, unlike that 
 in tea, turns a solution of ferrous sulphate green, and will not 
 precipitate one of gelatin. 
 
 22. Why does ivriting-fluid darken oti exposure to the 
 air? 
 
 It absorbs O, the iron changing to ferric oxide. 
 
 23. IfJiat causes the disagreeable smell of a smolder- 
 ing ^vick ? 
 
 A volatile substance, termed acrolein, is produced in the de- 
 composition of the oil. 
 
 24. IVJiy does ink corrode steel pens ? 
 
 The free sulphuric acid of the ink combines with the iron 
 of the pen. 
 
 * The tannic acid of the tea tans the albumen of the milk used in 
 seasoning the tea, forming flakes of real leather. It has been calculated 
 that an average tea-drinker, in this way, makes and drinks enough leather 
 each year to make a pair of shoes. The albumen of milk uniting with the 
 tannic acid of tea, softens its flavor. This is generally preferred to the 
 harsh, clear beverage. 
 
IN POPULAR CHEMISTRY. 105 
 
 25. How does a bird obtain the CaCO 3 for its egg 
 
 shells ? 
 
 (See chemistry of a lien's egg in Fireside Science.) 
 
 A common hen's egg is 95 per cent, carbonate of lime, one 
 per cent, phosphate of lime and magnesia, and two per cent, 
 animal matter. The shell would weigh over 100 grains, so that 
 a hen laying 100 eggs in a season would require nearly 1^ Ibs. 
 of CaCO 3 . The hen must in part secrete this from her food, 
 and in part gather it from the sand, pebbles, etc., she picks up 
 amid her incessant scratching and searching. 
 
 26. Why does new soap act on the hands more than 
 old ? 
 
 The spent lye, which contains the excess of alkali, gradu- 
 ally separates from the soap, leaving only the salts in which 
 the alkali is neutralized by the fatty acids. Also a more com- 
 plete combination takes place, whereby some free alkali is 
 taken up by the acids, perhaps before uncombined. The for- 
 mer statement is especially true in the case of soft or home- 
 made soap. 
 
 27. What is the shiny coat on certain leaves and fruits ? 
 
 A species of wax secreted by the plant. 
 
 28. Why does tiwpentine burn with so much, smoke ? 
 
 Because it contains an excess of carbon. 
 
 20. Wliy is the nozzle of a turpentine bottle so sticky ? 
 
 The turpentine on exposure to the air oxidizes, turning to 
 rosin. 
 
 30. Why does kerosene give more light than alcohol ? 
 
 It contains more carbon, which, when heated in the flame 
 of the burning H, gives out a white light. 
 
 31. IVliat is the antidote to oxalic acid ? Why ? 
 
 Magnesia or chalk, forming an insoluble oxalate. 
 
 32. Would you iveaken camphor spirits with ivater ? 
 
106 ANSWERS TO PRACTICAL QUESTIONS. 
 
 No ; since camphor is insoluble in dilute alcohol. The prin- 
 ciple is the same as that of the precipitation of lead from 
 dilute sulphuric acid. 
 
 35. What is the difference between rosin and resin ? 
 
 Rosin is an oxidized resin. Rosin is a species, and resin a 
 genus. 
 
 34. IVJiy does skim -milk look blue and new milk 
 white ? 
 
 The globules of butter contained in new milk reflect the 
 light, and so make it look white ; but when they are removed, 
 by the separation of the cream, more light is transmitted, and 
 only the blue is reflected to the eye. 
 
 35. Wliy does an ink-spot turn yellow after washing 
 with soap ? 
 
 The free alkali of the soap combines with the tannic acid 
 of the ink, leaving the oxide of iron (ferric oxide), which stains 
 the cloth yellow. 
 
ANSWERS 
 
 TO THE 
 
 QUESTIONS 
 
 IN THE 
 
 NEW DESCRIPTIVE ASTRONOMY. 
 
 32. 1. Hotv high is the North Star above your hori- 
 
 zon? 
 
 (See Astronomy, p. 218.) 
 
 It should be remembered that the North Star revolves 
 around the true North Pole at a distance of about 1 ; hence 
 it marks the exact height of the Pole above the horizon only 
 twice in twenty-four hours. 
 
 2. What is the sun's right ascension at the autumnal 
 equinox ? At the vernal equinox ? 
 
 At the vernal equinox, the sun is in Aries, and its R. A.=0. 
 At the autumnal equinox, it is in Libra, and its R. A. = 180. 
 
 3. What ^vas the first discovery made by the telescope ? 
 
 (See Astronomy, p. 20 ; articles in Appletons 1 Cyclopedia on Telescope 
 and Gt-alileo ; and, also, Routledge's History of Science, p. 107.) 
 
 Galileo's telescope was constructed on the principle of an 
 opera-glass. 
 
 4. How high above the horizon of any place are the 
 equinoctial points when they pass the meridian ? 
 
 (See Astronomy, note, p. 27.) 
 The co-latitude of the place. 
 
 5. Jupiter revolves around the sun in 12 of our years. 
 Assuming the earth's distance from the sun to be 93,OOO,- 
 OOO miles 9 compute Jupiter's distance by applying Kep- 
 ler's third law. 
 
 (See Astronomy, note, p. 19.) 
 
108 ANSWERS TO PRACTICAL QUESTIONS 
 
 If we square the period of any planet, expressed in years, 
 and extract the cube root of this product, the result will be the 
 mean distance from the sun, expressed in astronomical units, 
 i.e., in radii of the earth's orbit. Jupiter's period of 12 years 
 will give a result of 5.2028. 93,000,000 miles x 5.2028 = 483,- 
 860,400 miles. 
 
 6. The latitude of Albany is 42 39' N. ; what is the 
 sun's meridian altitude at that place ivJien it is in the celes- 
 tial equator ? 
 
 (See Astronomy, note, p. 27.) 
 
 90- 42 39'= 47 21'. 
 
 7. Wliat is the co-latitude of a place ? 
 
 (See Astronomy, note, p. 27.) 
 
 The co-latitude is the complement of the latitude. 
 
 8. Wliafis the declination of the zenith of the place in 
 which you reside ? 
 
 (See Astronomy, note, p. 27.) 
 
 It equals the latitude. 
 
 .9. Why are the stars generally invisible by day ? 
 
 (See Astronomy, p. 25.) 
 
 The stars would be visible in the day-time if it were not for 
 the atmosphere. Compare the description of a lunar sky, on 
 page 134 of the Astronomy. 
 
 10. Why is the ecliptic so called ? 
 
 (See Astronomy, note, p. 58.) 
 
 11. Who first taught that the earth is round ? 
 
 The discovery of the rotundity of the earth has been as- 
 cribed to Thales ; others attribute it to Aristotle. 
 
 12. IVliat is Astrology ? 
 
 A magic art that pretends to foretell events by means of 
 the stars. 
 
 13. How can ive distinguish the fixed stars from the 
 
 planets ? 
 
 (See Astronomy, pp. 2 and 203.) 
 
IN DESCRIPTIVE ASTRONOMY. 109 
 
 14. How long ivas the Ptolemaic system accepted? 
 
 It was taught in the schools for about 1400 years, or until 
 the time of Galileo the 17th century. 
 
 15. In ivhat respect did the Copernican system, differ 
 from the one now received ? 
 
 (See Astronomy, p. 14.) 
 
 10. For what is Astronomy indebted to Galileo? To 
 Neivton ? 
 
 Galileo discovered the structure of the moon ; the existence 
 of Jupiter's moons and their revolution around their primary ; 
 the stars of the milky way ; and the rotation of the sun on 
 its axis (as proved by the appearance of the spots). Newton 
 discovered the law of gravitation, and by means of it explained 
 the specific gravity of the planets, the cause of the tides, the 
 shape of the earth, the theory of precession of the equinoxes, 
 and the paths of the comets. Bead Brewster's Life of Newton; 
 also, Buckley's History of Natural Science. 
 
 17. What is the amount of the obliquity of the ecliptic ? 
 
 (See Astronomy, p. 29.) 
 
 18. Define Zenith. Nadir. Azimuth. Altitude. Equi- 
 noctial. Right Ascension. Declination. Equinox. Eclip- 
 tic. Colure. Solstice. Polar distance. Zenith distance. 
 The Zodiacs 
 
 These terms are defined under the various subjects on pp. 
 26-30 of the Astronomy. 
 
 IV. If the H.A.of the sun be 8O\ state in ^vhat sign he 
 is then located. 16O. 28O. 
 
 (See Astronomy, table on p. 31.) 
 
 1 sign = 30. 80 would locate the sun in Gemini ; 160, in 
 Virgo ; 280, in Capricornus. 
 
 2O. Why does the angle which the ecliptic makes with 
 the horizon vary ? 
 
 (See Astronomy, p. 29.) 
 
 The angle between the horizon and the celestial equator is 
 constant ; the ecliptic being oblique to the equator, the angle 
 that it makes with the horizon must vary as it revolves. 
 
110 ANSWERS TO PRACTICAL QUESTIONS 
 
 21. W7iy is the angle which the celestial equator makes 
 with the horizon constant ? 
 
 (See Astronomy, p. 29.) 
 
 The celestial equator is perpendicular to the axis of the 
 heavens, and hence all parts of it make the same angle with 
 the celestial axis and with the horizon. 
 
 I 98 1. Would the earth rise and set to a Lunarian ? 
 
 (See Astronomy, p. 134.) 
 
 The earth would not rise or set, as the moon does with us, 
 but would merely oscillate to and fro through a few degrees. 
 A Lunarian would see the earth constantly in the sky, under- 
 going all the phases the moon presents to the earth. But when 
 it is full moon to us, it is new earth on the moon. During the 
 first and last quarters, the changes would occur during the day- 
 time ; during the second and third, in the night. The rapid 
 rotation of the earth, repeated fifteen times during a lunar 
 night, must greatly diversify the appearance of the earth. See 
 Olmstead's Letters on Astronomy, p. 180. 
 
 2. Could there be a transit of Jupiter ? 
 
 (See Astronomy, p. 67.) 
 
 No. Jupiter is a superior planet. 
 
 3. IVliy does Mars' inner-moon rise in the west ? 
 
 (See Astronomy, note on p. 153.) 
 
 This satellite performs a revolution in its orbit in less than 
 half the time that Mars revolves on its axis. In consequence, 
 to the inhabitants of Mars, it would seem to rise in the west 
 and set in the east. The revolution of the moon around the 
 earth and of the earth on its axis, are both from west to east ; 
 but, the latter revolution being the more rapid, the apparent 
 diurnal motion of the moon is from east to west. In the case 
 of the inner satellite of Mars, however, this is reversed, and it 
 therefore appears to move in the actual direction of its orbital 
 motion. The rapidity of its phases is also equally remarkable. 
 It is less than two hours from new moon to first quarter. New- 
 comb and Holden's Astronomy, p. 339. 
 
IN DESCRIPTIVE ASTRONOMY. Ill 
 
 4. In wJiat part of the ski/ do you always look for the 
 planets ? 
 
 Within the limits of the Zodiac. A few of the asteroids 
 only pass outside this belt of the heavens. 
 
 .5. Show how it was impossible for the darkness that 
 occurred at the time of the Crucifixion of Christ to have 
 been caused by an eclipse of the sun. 
 
 The Feast of the Passover took place at full moon. "With 
 the Jews, a month began when the new moon was seen. Per- 
 sons were appointed to watch, about the time it was expected, 
 on the tops of mountains. As soon as they saw its light, they 
 gave notice by sounding trumpets and building fires." Kevin's 
 Biblical Antiquities. 
 
 0. Is there any danger of a collision between the earth 
 
 and a comet ? 
 
 (See Astronomy, p 192.) 
 
 A collision between the earth and a comet must be a rare 
 occurrence. Babinet computed that one would strike the earth, 
 on the average, every 15,000,000 years. There are certainly, 
 however, comets whose orbits cross the earth's path, and if we 
 should happen to reach the crossing at the same time with one 
 of them, there would be a collision. We should probably never 
 know of the event unless we were watching for it. 
 
 7. Hoiv are aerolites distinguished ? 
 
 (See Astronomy, pp. 177, 178.) 
 
 Aerolites, when found, generally have an exterior crust of 
 fused material, presenting a glossy, pitch-like appearance. An 
 analysis of the interior commonly presents a combination of 
 elements that is so characteristic as to identify the body as an 
 aerolite even when not seen to fall. Large masses have been 
 found in Northern Mexico which are thus known to be of me- 
 teoric origin. 
 
 " The meteoric stones may be divided into two distinct 
 groups meteoric iron, and meteoric stones proper. 
 
 " 1. Meteoric iron is an alloy of iron and nickel, containing 
 about 10 per cent, of nickel, and small quantities of cobalt, 
 
112 ANSWERS TO PRACTICAL QUESTIONS 
 
 manganese, magnesium, tin, copper, and carbon. This alloy has 
 not been found among terrestrial minerals. 
 
 " 2. The meteoric stones proper are composed of minerals 
 of volcanic origin, and such as are found abundantly in terres- 
 trial lavas and trap-rocks, viz. : 
 
 Magnetic iron, Olivine, 
 
 Sphene, Anorthite, 
 
 Chrome iron, Labradorite, 
 
 Apatite (?), Augite, 
 
 together with a varying proportion of the meteoric iron-nickel 
 alloy." Haughton's Astronomy. 
 
 8. When do ive see the old moon in the ivest after sun- 
 rise ? 
 
 (See Astronomy, p. 127.) 
 
 .9. When do we see the moon high in the eastern sky in 
 the afternoon before the sun sets ? 
 
 (See Astronomy, p. 127.) 
 
 During the second quarter, before she comes into opposition. 
 
 10. When is a planet morning, and when evening, 
 
 star ? 
 
 (See Astronomy, pp. 65, 70.) 
 
 11. Is the sun really hotter in summer than in ^vinter ? 
 
 (See Astronomy, p. 101.) 
 
 12. IVliy is a planet invisible at conjunction ? 
 
 (See Astronomy, p. 65.) 
 
 13. Must an inferior planet always be in the same part 
 of the sUy as the sun ? A superior planet ? 
 
 (See Astronomy, pp. 64 and 67.) 
 
 14. IVJty, in summer, does the sun, at rising and at set- 
 ting, shine on the north side of certain houses ? 
 
 Since at the summer solstice the sun rises and sets north of 
 the E. and "W. points, it will rise and set on the north side of 
 a house which stands exactly N. and S. At the winter solstice 
 the sun rises and sets S. of the E. and W. points. 
 
 15. Wliat effect does the volume of a planet have upon 
 the force of gravity at its surface ? 
 
 (See Astronomy, pp. 40, 80.) 
 
IN DESCRIPTIVE ASTRONOMY. 113 
 
 16. In what part of the heavens do we see the new 
 moon ? The old moon ? The crescent moon ? 
 
 (See Astronomy, p. 127 et seq.) 
 
 It is a very interesting experiment to notice how soon after 
 conjunction we can observe the new moon. Observers have de- 
 tected her when twenty-three hours old, and an instance is on 
 record of the moon's thin crescent being seen early one morn- 
 ing before sunrise, and after sundown the following day. 
 
 17. What is the Golden Number in the almanac? 
 
 (See Astronomy, p. 145.) 
 
 18. Why do we have more lunar than solar eclipses ? 
 
 (Soc Astronomy, p. 146.) 
 
 Really, solar eclipses occur more frequently than lunar eclipses, 
 but the latter are . of tener seen at any particular place, because 
 they are visible over a larger area of territory on the earth. 
 
 19. In ivhat direction do the horns of the moon turn ? 
 
 (See Astronomy, p. 127.) 
 
 20. Is the " tidal wave " a progressive movement of 
 
 the ivater ? 
 
 (See Astronomy, note, p. 148.) 
 
 The wind raises the particles of water, and gravity draws 
 them back again. They thus vibrate up and down, but do not 
 advance. The forward movement of the wave is an illusion. 
 The form of the wave progresses, but not the water of which 
 it is composed, any more than the thread of the screw which 
 we turn in our hand, or the undulations of a rope or carpet 
 which is shaken, or the stalks of grain which bend in billows 
 as the wind sweeps over them. Near the shore the oscillations 
 are shorter, and the waves, unbalanced by the deep water, are 
 forced forward till the lower part of each one is checked by the 
 friction on the sandy beach, the front becomes well-nigh ver- 
 tical, and the upper part curls over and falls beyond. 
 
 21. Why does the sun "cross the line" in some years 
 on March 21, and, in others, on March 22 ? 
 
 (See Astronomy, p. 99.) 
 
 Leap-year also throws the dates back one day. 
 
114 ANSWERS TO PRACTICAL QUESTIONS 
 
 22. Do we ever see the sun where it really is ? 
 
 (See Astronomy, p. 114.) 
 
 Both refraction and aberration of light change the apparent^ 
 place of the sun. 
 
 23. " At Edinburgh) Scotland, there are times when 
 the sun rises at 3% o'clock A.M., and sets at 8^ o'clock 
 P.M., and the twilight lasts the entire night. 9 ' When and 
 
 why is this ? 
 
 (See Astronomy, p. 116.) 
 
 The latitude of Edinburgh is 55 57'. Any place north of 
 48 33' will have twilight at midnight in midsummer ; for 90 
 23 27' (the sun's declination) 18 3 (at which twilight ceases) 
 = 48 33'. The hours named in the problem are the times for 
 the rising and setting of the sun at Edinburgh at the summer 
 solstice. 
 
 24. Which is the longest day of the year ? 
 
 (See Astronomy, p. 99.) 
 
 The summer solstice points out the longest day of the year. 
 
 25. Ts the moon nearer to us ivlien it is at the horizon , 
 or at the zenith ? 
 
 (See Astronomy, p. 124.) 
 
 The moon is nearer to ur, when it is at the zenith than 
 when it is at the horizon. 
 
 26. How many solar eclipses ivould happen each year 
 if the orbits of the sun and the moon ^vere in the same 
 plane ? 
 
 (See Astronomy, p. 138.) 
 
 In that case a solar eclipse would occur every new moon. 
 
 27. Is there any heat in moonlight ? 
 
 (See Astronomy, p. 125.) 
 
 28. Can ive see the moon during a total eclipse ? 
 
 (See Astronomy, p. 146.) 
 
 29. WTiicJi of the planets are repeating a portion of the 
 earth's history ? 
 
 Spectrum Analysis renders it possible, perhaps probable, 
 that Jupiter and Saturn, and, may be, Uranus and Neptune, 
 
IN DESCRIPTIVE ASTRONOMY. 115 
 
 have not yet attained that degree of density which must neces- 
 sarily precede the formation of a solid surface. They are, 
 therefore, now in a geologic age similar to that in which the 
 earth existed before its crust had become solidified. (See Schel- 
 len's Spectrum Analysis, p. 337.) 
 
 SO. Hoiv many titties does the moon turn on her axis 
 
 each year ? 
 
 (See Astronomy, p. 123.) 
 
 The moon turns on her axis once each month. 
 
 31. Can you explain the different signs used in the 
 
 almanac ? 
 
 (See "Astronomical Signs" in the Dictionary.) 
 
 32. Shoiv how the moon is a prophecy of the earth's 
 future. 
 
 The moon is a worn-out globe, and presents the same ap- 
 pearance that the earth will probably offer ages hence. 
 
 33. Does the sun really rise and set ? 
 
 (See Astronomy, pp. 14, 87.) 
 
 No. This is only an optical illusion, being an illustration of 
 our tendency to transfer motion. 
 
 34. Are the bright portions of the noon mountains or 
 plains ? 
 
 The lofty portions, or mountains, of the moon reflect the 
 light to the earth most strongly, and hence appear the bright- 
 est. The deep valleys, lying in shadow, look dark. 
 
 35. Which of the heavenly bodies are self-luminous ? 
 
 (See above, Question 29 ; also Astronomy, note, p. 163.) 
 Jupiter and Saturn probably emit light, at least from the 
 brighter spots of their surface. Read Newcomb's Astronomy, p. 
 342. 
 
 36. Why is not a solar eclipse visible over the whole 
 
 earth ? 
 
 (See Astronomy, p. 140.) 
 
 37. What is meant by the "mean distance" of a 
 planet ? 
 
 The "mean distance" is the average distance. 
 
116 ANSWERS TO PRACTICAL QUESTIONS 
 
 38. What keeps the earth in motion around the situ ? 
 
 (See Astronomy, p. 22.) 
 
 According to the First Law of Motion, "Every body con- 
 tinues in its state of rest or of uniform motion in a straight 
 line, except in so far as it may be compelled by impressed 
 forces to change that state." 
 
 .7.9. Do we ever see the sun after it sets ? 
 
 (Sec Astronomy, p. 114.) 
 
 The refraction of the atmosphere tends to raise all objects 
 toward the zenith, and, at the horizon, this is no less than 35', 
 or 3' more than the mean diameter of the sun (32'). 
 
 40. When does the earth move the most rapidly in its 
 orbit ? 
 
 (See Astronomy, p. 18.) 
 The earth moves most rapidly in perihelion. 
 
 4:1. Have ive conclusive evidence that any planet is in- 
 habited ? 
 
 (See Astronomy, p. 61; also note, p. 297.) 
 
 May it not be that the same lavish hand that scatters flow- 
 ers and seeds in such profusion (not one in a thousand coming 
 to the perfection and end of its being), sows space with worlds, 
 a few only reaching the full fruition of life ? 
 
 42. When is tivilight the longest? The shortest? Why? 
 
 (See Astronomy, p. 116.) 
 
 Twilight is usually reckoned to last until the sun's depres- 
 sion below the horizon amounts to 18 ; this, however, varies ; 
 in the tropics a depression of 16 or 17 is sufficient to put an 
 end to the phenomenon, but in England a depression of 17 to 
 21 is required. The duration of twilight differs in different 
 latitudes ; it varies also in the same latitude at different sea- 
 sons of the year, and depends, in some measure, on the meteoro- 
 logical condition of the atmosphere. Strictly speaking, in the 
 latitude of Greenwich there is no true night from May 22 to 
 July 21, but constant twilight from sunset to sunrise. Twilight 
 reaches its minimum three weeks before the vernal equinox, 
 and three weeks after the autumnal equinox, when its duration 
 
IN DESCRIPTIVE ASTRONOMY. 117 
 
 is 1 hr. 50 min. At midwinter it is longer by about seven- 
 teen minutes ; but the augmentation is frequently not percepti- 
 ble, owing to the greater prevalence of clouds and haze at 
 that season of the year, which intercept the light, and hinder 
 it from reaching the earth. The duration is least at the equa- 
 tor (1 hr. 12 min.), and increases as we approach the poles ; 
 for at the former there are two twilights every twenty-four 
 hours, but at the latter only two in a year, each lasting about 
 fifty days. At the north pole the sun is below the horizon for 
 six months, but from January 29 to the vernal equinox, and 
 from the autumnal equinox to November 12, the sun is less 
 than 18 below the horizon ; so that there is twilight during 
 the whole of these intervals, and thus the length of the actual 
 night is reduced to 21 months. The length of the day in these 
 regions is about six months, during the whole of which time 
 the sun is constantly above the horizon. The general rule is, 
 that to the inhabitants of an oblique sphere the twilight is longer in 
 proportion as the place is nearer the elevated pole, and the sun is 
 farther from the equator on the side of the elevated pole. Cham- 
 bers' Astronomy. 
 
 When the sun rises or sets most obliquely to the horizon, 
 then the least time is required to pass through the necessary 
 18, and, of course, the length of twilight is the least. When 
 the sun rises or sets least obliquely, the most time is required 
 to pass through 18, and the length of twilight is greatest. If 
 the sun's path is perpendicular to the horizon, the sun will 
 pass over the 18 in 1 hr. 12 min.; for 15= 1 hr.; and hence 
 18 =1^ hr. 
 
 43. What is a moon ? 
 
 A moon is a secondary body, or satellite, revolving about a 
 primary body, or planet. 
 
 44. To a person in the south temperate zone, where 
 would the sun be at noon ? 
 
 On the meridian north of the observer. 
 
 45. Is it correct to say that the moonrevolvcs about the 
 earth 9 ivhen ive know tit at f according to the law of Phys- 
 
118 ANSWERS TO PRACTICAL QUESTIONS 
 
 icSf they must both revolve about their common center of 
 
 gravity ? 
 
 (See Astronomy, note, p. 200.) 
 
 The earth is not stationary as regards the moon, for both 
 it and our satellite revolve together about their common center 
 of gravity. Again, it is not the earth alone which revolves 
 about the sun in the elliptical orbit, but this common center of 
 gravity. The sun, also, is not stationary, but it and the planets 
 revolve about the common center of gravity of the whole 
 system. 
 
 46. During a transit of Venus, do we see the body of 
 the planet itself on the face of the sun ? 
 
 (See Astronomy, p. 277.) 
 
 During a transit, Venus appears as " a perfectly round Nock 
 spot on the disk of the sun." The planet turns its unillumined 
 side toward us, and is, strictly speaking, invisible. 
 
 47. How many real motions has the sun ? How many 
 apparent ones ? 
 
 It has two real motions : one around its axis, and one with 
 the solar system around the Pleiades. It has three apparent 
 motions : one along the ecliptic, its yearly motion ; one through 
 the heavens, its daily motion ; and one north and south. 
 
 48. Hoiv many real motions has the earth ? 
 
 Three. One on its axis ; one around the sun ; and a third, 
 its "wabbling motion," which causes Precession. 
 
 49. Can an inferior planet have an elongation of9O ? 
 
 No. Venus recedes only 48 from the sun. 
 
 50. How do ive know the intensity of the sun's lit/lit on 
 the surface of any of the planets ? 
 
 The intensity of the heat and light varies inversely as the 
 square of the distance. 
 
 51. IVJiy is the Tropic of Cancer placed where it is ? 
 
 Because it is the farthest place north where the sun is ever 
 seen directly overhead. 
 
IN DESCRIPTIVE ASTRONOMY. 119 
 
 52. What planets would float in water ? 
 
 According to Chambers' Astronomy, the density of Saturn 
 is .68 that of water ; Uranus, .99 ; Neptune, .96. According to 
 Newcomb, Saturn's density is .75. 
 
 53. How must the moons of Jupiter appear during 
 their transit across the disk of that planet ? 
 
 The satellites appear on the disk of their primary as round 
 luminous spots, preceded or followed by their shadows, which 
 show as round black or blackish spots. CHAMBERS. 
 
 54. " The shadow of the satellite precedes the satellite 
 itself when Jupiter is passing from conjunction to oppo- 
 sition) but follows it between opposition and conjunc~ 
 tion." Explain. 
 
 "When actually in conjunction, the shadow is in a right line 
 with the satellite, and the two may be superposed. 
 
 55. What facts point to the conclusion that Mars may, 
 perhaps, have passed his planetary prime ? 
 
 The proportion of land and water, and the appearance of 
 the seas, all point to a conclusion somewhat similar to the one 
 stated in the following quotation : 
 
 " Mars' orbit being outside the earth's, he was probably 
 formed earlier. The mass of Mars is not much more than \ 
 the earth's, and the surface about |- ; if he possessed the same 
 degree of heat as the earth, he would have only \ the amount 
 to radiate, and the supply would not last so long. Though 
 having only \ the surface of the earth, he would still cool off 3 
 times as rapidly as the earth. Mars must, therefore, be at 
 least three times as far on the way toward planetary decrepi- 
 tude and death as our earth." Proctor's Poetry of Astronomy. 
 
 50. Why may ^ve conceive that Saturn and Jupiter are 
 yet in their planetary youth ? 
 
 (See Astronomy, note, p. 163.) 
 
 Vast planets, like Saturn and Jupiter, must have required 
 for cooling a far longer time than the earth, and thus the va- 
 rious stages of development would occupy a much greater 
 
120 ANSWERS TO PRACTICAL QUESTIONS 
 
 length of time. (Read Proctor's " When the Sea was Young," 
 in Poetry of Science.) 
 
 57 Show how, if the Nebular Hypothesis be accepted, 
 the fashioning of a planet must require an enormous 
 
 length of time. 
 
 (See Astronomy, p. 255.) 
 
 The experiments of Bischof upon basalt show that the earth 
 would require 350 millions of years to cool down from 2,000 
 C to 200 0. This enormous period would represent only one 
 stage in the process of the earth's development. (Read Win- 
 chell's World Life.) 
 
 58. Do we know the cause of gravitation ? 
 
 (See Astronomy, note, p. 23.) 
 
 283 1. In what constellation is Job's Coffin? The 
 Letter Y? The Scalene Triangle? The Dipper? The 
 Kids ? The Triangles ? 
 
 Job's Coffin is in Delphinus ; the Letter Y, in Aquarius ; 
 the Scalene Triangle, in Aries ; the Big Dipper, in Ursa Major ; 
 the Kids, in Auriga; and the Triangles, between Almach and 
 Arietis. 
 
 2. Name some facts in the solar system for ivhich the 
 Nebular Hypothesis fails to account. 
 
 It is very difficult to explain, on the basis of the Nebular 
 Hypothesis, why the axes of certain of the planets are so 
 greatly inclined, and, especially, why the velocity of the rota- 
 tion of the inner moon of Mars should so far exceed that of 
 Mars itself. 
 
 3. Which is probably hotter, a yellow or a red star ? 
 
 (See Astronomy, note, p. 241.) 
 
 When we heat a piece of iron, it first becomes red-hot, 
 then, as the temperature rises, other colors appear, until, 
 finally, it becomes dazzling white. (See Physics, p. 183.) 
 
 4. Are any of the stars likely to collide with each other ? 
 
 Nothing strikes the astronomer more forcibly than the 
 thought of the desolateness of space. A vast gulf, more than 
 
IN DESCRIPTIVE ASTRONOMY. 121 
 
 twenty-five trillions of miles in width, separates Neptune from 
 the nearest fixed star. It has been estimated that the average 
 distance between two of the sixty millions of fixed stars visible 
 to our largest telescopes, is about nine millions of millions of 
 miles. With this amount of "elbow-room," a collision between 
 any two such remote neighbors would be almost impossible. 
 Yet, Sir Wm. Thomson remarks: "It is as sure that collisions 
 must occur between great masses moving through space, unless 
 guided in their paths, as it is that ships, steered without intelli- 
 gence, could not cross and recross the Atlantic for thousands of 
 years with immunity from collisions." 
 
 t>. Is the real day longer or shorter than the apparent 
 one? 
 
 (See Astronomy, p. 264.) 
 
 6. Do we ever see the stars ? . 
 
 (See Astronomy, p. 203.) 
 
 7. What fined star is nearest the earth ? 
 
 (See Astronomy, pp. 204, 241.) 
 
 8. Hoiv often is Polaris on the meridian of a place? 
 
 As Polaris revolves about the true pole in a circle, the 
 radius of which is nearly l|-, it follows that in every twenty- 
 four hours it is once on the meridian below the pole, and, also, 
 once above it. The diameter of this circle is the length of 
 Orion's Belt, the stars at the right and the left of the central 
 one representing the distance the polar star goes to the right 
 and left of the pole. 
 
 9. How do we Jcnow that the stars are suns ? 
 
 (See Astronomy, pp. 205, 261.) 
 Spectrum analysis proves this to be the fact. 
 
 10. Can a watch keep apparent time? 
 
 (See Astronomy, p. 265.) 
 
 11. How could a child be eight years old before a re- 
 turn of its birthday ? 
 
 An infant born on Feb. 29, 1796, did not have a birthday 
 proper until Feb. 29, 1804, since the year 1800, not being 
 
122 ANSWERS TO PRACTICAL QUESTIONS 
 
 divisible by 400, was not a leap-year. Many other such dates 
 may be named. 
 
 12. When will a watch and a sun-dial agree ? 
 
 (See Astronomy, p. 265.) 
 
 13. What star will be the Pole Star next after Polaris ? 
 
 (See Astronomy, p. 217.) 
 
 14. Why is the birthday of Washington celebrated on 
 Feb. 22, ivhen he ivas born Feb. 11, 1732 (O. 8.} ? 
 
 (See Astronomy, note, p. 312.) 
 
 15. Does the tide have any effect on the length of the 
 
 day? 
 
 (See Astronomy, notes, pp. 89, 303.) 
 
 16. Will the jBiff Dipper always look as it does now ? 
 
 (See Astronomy, note, p. 217.) 
 
 The following figure, taken from Proctor's Easy Star Les- 
 sons, represents the location of the seven stars comprising the 
 Big Dipper, as they will be seen 100,000 years hence : 
 
 */? 
 
 17 Hoiv many times docs the earth turn on its axis 
 every year ? 
 
 (See Astronomy, p. 264.) 
 
 18. Does the spectroscope tell us any thing concerning 
 the constitution of the moon, or any of the planets ? 
 
 These bodies shine, in general, by reflected light ; therefore, 
 the light examined comes from the sun. By comparing this re- 
 flected light with solar light, the change produced by the planet's 
 atmosphere may be detected. The lunar spectrum exactly 
 accords with the solar spectrum. The spectra of Venus, Mars, 
 Jupiter, and Saturn contain absorption lines indicating aqueous 
 vapor. Bead Schellen's Spectrum Analysis, p. 333. 
 
 19. When the United States bought Alaska from Rus- 
 sia, the calendar used there was found to be one day ahead 
 of our reckoning. Why was this ? 
 
IN DESCRIPTIVE ASTRONOMY. 123 
 
 One going around the world westward will lose a day in 
 his reckoning ; one going eastward will gain a day. The Alaska 
 calendar was established by those who came from the West to 
 this continent, and their Tuesday corresponded to our Monday. 
 
 20. Why do the dates of the solstices and equinoxes 
 vary a day in different years ? 
 
 (See Astronomy, p. 99.) 
 
 Leap-year advances the dates one day. 
 
 21. Why are not forenoon and afternoon of the same 
 day, as given in the almanac, of equal length ? 
 
 (See Astronomy, p. 265.) 
 
 Apparent noon marks the middle of the day ; but mean 
 noon may be either before or after the apparent noon; i.e., 
 the time when the real sun is on the meridian. 
 
 22. In ivhat part of the heavens (in our latitude) do 
 the stars apparently move from west to east? 
 
 The northern circumpolar constellations revolve about the 
 North Pole, and, during a part of their paths, they apparently 
 move from west to east. 
 
 23. What year was only nine months and sioc days 
 
 long ? 
 
 (See Astronomy, note, p. 312.) 
 
 24. What day ivill be the last day of the nineteenth 
 century ? 
 
 December 31, 1900. 
 
 25. If one should watch the sky, on a winter's evening, 
 from 6 P.M. to 6 A.M., ivhat portion of the celestial 
 sphere would he be able to see ? 
 
 All that is ever seen in his latitude. 
 
 26. How do ive know that the moon has little, if any, 
 atmosphere ? 
 
 Because when the moon occults a star, there is no refrac- 
 tion of the star's true place. 
 
124 ANSWERS TO PRACTICAL QUESTIONS 
 
 27. lit, Greenland, at what part of the year will the 
 midnight sun be seen due north ? 
 
 At all places whose latitude is 66 30' N., the sun will be 
 on the northern horizon at midnight of the summer solstice. 
 At all places north of the Arctic Circle the sun will remain 
 above the horizon, even at midnight, for a certain portion of 
 the summer, the number of days increasing with the latitude. 
 Read Ball's Elements of Astronomy, p. 142. 
 
 28. Can you give any other proof of the rotundity of 
 the earth 9 besides that named in the teoct (p. 85) ? 
 
 (See Astronomy, note, p. 299.) 
 
 A sphere is the only body that always presents to us the 
 form of a circle, no matter in what direction we view it. At 
 sea, the circular form of the horizon is even more evident than 
 on land. 
 
 29. Point out the error in tJie following passage from 
 Byron's "Darkness," where the poet, in describing the 
 effect of tJie sun's destruction, says : 
 
 " I had a dream, . . . 
 
 . . . which, was not all a dream ; 
 The bright sun was extinguished, and the stars 
 Did wander darkling in the external space 
 Eayless and pathless." 
 
 The fixed stars would be unaffected by the extinction of the 
 sun's light. 
 
 30. Explain the rernarh of the First Carrier in Scene 
 I., Act II., King Henry IV. : "An't be not four by the day, 
 I'll be hanged: Charles' wain is over the new chimney." 
 
 (See Astronomy, note, p. 311.) 
 
 Since the two great stars which mark the summit and the 
 foot of the Cross have nearly the same right ascension, it fol- 
 lows that the constellation is almost perpendicular at the mo- 
 ment when it passes the meridian. This circumstance is known 
 to every nation that lives beyond the tropics or in the Southern 
 Hemisphere. It has been observed at what hour of the night, 
 in different seasons, the Cross of the south is erect or inclined. 
 It is a time-piece that advances very regularly near four min- 
 

 AV DESCRIPTIVE ASTRONOMY. 125 
 
 utes a day, and no other group of stars exhibits to the naked 
 eye an observation of time so easily made. How often have 
 we heard our guides exclaim in the savannas of Venezuela, or 
 in the desert extending from Lima to Truxillo, "Midnight is 
 past, the Cross begins to bend ! " How often those words re- 
 minded us of that affecting scene, where Paul and Virginia, 
 seated near the sources of the river of Lataniers, conversed 
 together for the last time, and where the old man, at the sight 
 of the Southern Cross, warns them that it is time to separate. 
 HUMBOLDT. 
 
 31. Why does not the earth move with equal velocity in 
 all parts of its orbit ? 
 
 Because at perihelion it is nearer the sun than when in 
 aphelion, and hence the attraction is stronger. 
 
 32. How many Jovian-years old are you ? 
 
 A Jovian-year equals 11.86 earth-years. 
 
 33. Why is the sky blue ? 
 
 The blue light of the firmament is light reflected by solid 
 particles generally of aqueous vapor in the air. It is notice- 
 able that early in the morning and late at night, when the 
 sun's rays fall obliquely upon the atmosphere, they are polar- 
 ized by reflection. The reflected light is blue ; the transmitted 
 light of the sky is orange or red. (Read Tyndall's Light, p. 
 152.) 
 
 34. At ivhat season of the year does CJiristmas occur in 
 
 Australia ? 
 
 (See Astronomy, Art. vii., p. 98.) 
 
 35. Wliat causes the apparent movement of the sun 
 nortJi and south ? 
 
 (See Astronomy, p. 95.) 
 
 It is caused by the fact that the axis of the earth is inclined 
 to the plane of the ecliptic, while the earth is revolving about 
 the sun. 
 
 36. On what part of the earth is the twilight tlie long- 
 est? Tlie shortest? 
 
 (See Astronomy, p. 116 ; Manual, p. 116.) 
 
126 ANSWERS TO PRACTICAL QUESTIONS 
 
 " Where the air is unusually full of condensed vapor, as 
 occurs in polar regions, the twilight is greatly lengthened ; 
 where the air is unusually dry, as occurs in the tropics, twilight 
 is said sometimes to be shortened to fifteen minutes." 
 
 37. Name the causes which make our summer longer 
 than winter. 
 
 (See Astronomy, p. 102.) 
 
 38. Why is not total darkness produced when a dense 
 cloud passes between us and the sun ? 
 
 (See Astronomy, p. 117.) 
 
 39. Why does the time of the tide vary each day ? 
 
 (See Astronomy, p. 148.) 
 
 40. Why is an annular longer than a total eclipse ? 
 
 (See Astronomy, p. 140.) 
 
 4:1. Why is it colder in winter than in summer ? 
 
 (See Astronomy, pp. 97, 98.) 
 
 42. Do the solar spots affect our iveather ? 
 
 (See Astronomy, p. 48.) 
 
 43. Can the moon be eclipsed in the day-time ? 
 
 (See Astronomy, p. 114.) 
 
 44. Why are the sidereal days of uniform length ? 
 
 Because of the almost absolute uniformity of the earth's 
 rotation. 
 
 45. Why are not the solar days of uniform length ? 
 
 (See Astronomy, p. 266.) 
 
 46. What do the moon 9 s phases prove ? 
 
 The moon's phases prove that she is spherical, and shines 
 by the reflected light of the sun. 
 
 47. Why do the sun and moon appear flattened when 
 
 near the horizon ? 
 
 (See Astronomy, p. 115.) 
 
 48. How many stars can we see with the naked eye ? 
 
 No one sees more than 6,000, and few more than 4,000 stars. 
 
'IN DESCRIPTIVE ASTRONOMY. 127 
 
 49. Is there ever an annular eclipse of the moon ? 
 
 (See Astronomy, p. 146.) 
 
 50. " While the sun rises and sets 365 times, a star 
 rises and sets 366 times." Explain. 
 
 /, p. 264.) 
 
 51. How many moons are there in the solar system ? 
 
 Twenty have been discovered. 
 
 52. What causes the twinkling of the stars ? 
 
 (See Astronomy, p. 207.) 
 
 Some attribute the twinkling of the stars to the inequality 
 of refraction due to the constant changes in the density of the 
 air, produced by the constant changes in the heat. 
 
 53. Name some of the uses of the stars. 
 
 (See Astronomy, pp. 212, 285.) 
 
 54. Describe the methods by which we determine the 
 distance of the sun from the earth. 
 
 (See Astronomy, p. 275.) 
 
 55. Why do not the signs and the constellations of the 
 
 Zodiac agree ? 
 
 (See Astronomy, pp. 106, 211.) 
 
 56. Wlien we look at the North Star, how long since the 
 light that enters our eye has left that body ? 
 
 (See Astronomy, p. 218.) 
 
 57. In what direction does a comet's tail generally 
 
 point ? 
 
 (See Astronomy, note, p. 306.) 
 
 58. What is the cause of shooting stars ? 
 
 (See Astronomy, p 182.) 
 
 59. Why does the crescent moon appear larger than 
 the dark body of the moon ? 
 
 (See Astronomy, p. 123.) 
 
 60. THiat is the real path of the moon ? 
 
 (See Astronomy, pp. 123, 301.) 
 
 61. What ^vould be the result if the aocis of the earth 
 were parallel to the plane of its orbit ? 
 
 (Sec Astronomy, Article xx., p. 103.) 
 
128 ANSWERS TO PRACTICAL QUESTIONS 
 
 62. Do we see the same stars at different seasons of the 
 
 year ? 
 
 (See Astronomy, pp. 92, 93.) 
 
 63. Why do we not perceive the earth's motion in 
 space ? 
 
 Because all the objects around us partake of its motion. 
 
 64. Did the earth ever shine as a star ? Does it now 
 shine as a planet ? 
 
 The earth, doubtless, shone as a star while it was yet a 
 glowing mass ; now, it reflects the sun's light, like the other 
 planets. 
 
 65. IVJiat is the nebular hypothesis ? 
 
 (See Astronomy, p. 255.) 
 
 66. JVJiat is the cause of the solar spots ? 
 
 (See Astronomy, p. 54.) 
 
 6*7. Would it make the new moon " drier " or " wetter " 
 if the moon's path ran north of, instead of on,, the ecliptic 
 at the time of new moon ? 
 
 The moon's latitude varies from 5 N. to 5 S. (exactly 5 
 8' 47" 9). If the new moon were 5 1ST., this would increase 
 the angle of 72^ (note, p. 30) to 77, and thus make the line 
 joining the moon's cusps more nearly parallel to the horizon. 
 It may be easily seen that whenever the plane of the lunar 
 orbit lies so as to carry the moon past conjunction above the 
 sun, then the crescent is more nearly horizontal ; when below, 
 then it is more nearly vertical. 
 
 68. Under what conditions are we accustomed to trans- 
 fer motion ? 
 
 (See Astronomy, pp. 85, 86.) 
 
 69. Wliy do not the planets twinkle ? 
 
 (See Astronomy, note, p. 207.) 
 
 70. IVliy is the horizon a circle ? 
 
 (See Manual, p. 124, Question 28.) 
 
 7 ! What causes are gradually increasing the length of 
 
 the day ? 
 
 (See Astronomy, notes, pp. 89, 303.) 
 
DESCRIPTIVE ASTRONOMY. 
 
 129 
 
 year ? 
 
 IVliat distance does the moon gain in her orbit each 
 
 (See Astronomy, notes, pp. 89, 302.) 
 
 75. State the general argument which renders it prob- 
 able that other worlds are inhabited. 
 
 (See Astronomy, p. 63; also, note, p. 297.) 
 
 74. Illustrate the uniformity of Nature. What thought 
 does this suggest ? 
 
 (See Astronomy, p. 55; also, note, p. 297.) 
 
 So far as we can judge, the laws of Nature, the properties 
 of matter, etc., are uniform throughout the universe, and re- 
 veal the workmanship of one Creator. 
 
 75. At ^vhat rate are we traveling througJi space? 
 How is this determined ? 
 
 The mean orbital velocity of the earth is 18.4 miles per 
 second. Knowing the circumference of its yearly path, the rate 
 of motion is easily calculated. 
 
 76. Why does the length of a degree of latitude increase 
 in going from the equator toward either pole of the earth ? 
 
 Because the form of the earth is not perfectly spherical, but 
 is flattened at the poles and bulged at the equator. 
 
 LENGTH OF DEGREE OF LATITUDE. 
 
 COUNTRY. 
 
 LATITUDE. 
 
 LENGTH OF 
 DEGREE. 
 
 Sweden 
 
 66 C 
 66 
 58 
 56 
 54 
 54 
 52 
 52 
 52 
 46 
 44 
 42 
 39 
 16 
 12 
 1 
 33 
 35 
 
 20' 
 19 
 17 
 3 
 58 
 8 
 32 
 35 
 2 
 52 
 51 
 59 
 12 
 8 
 32 
 31 
 18 
 43 
 
 10" N. 
 37 
 37 
 55-5 
 26 
 13-7 
 16'6 
 45 
 19'4 
 2 
 2*5 
 
 
 21-5 
 20-8 
 0-4 S. 
 30 
 20 
 
 Feet. 
 365744 
 367086 
 365368 
 365291 
 365420 
 365087 
 365300 
 364971 
 364951 
 364872 
 364572 
 364262 
 363786 
 363044 
 362956 
 363626 
 364713 
 364060 
 
 Sweden 
 
 Russia 
 
 Russia 
 
 Prussia .... 
 
 Denmark .... 
 
 Hanover .... 
 
 England. 
 
 England 
 
 Prance 
 
 France 
 
 Rome. . .... 
 
 America . . . 
 
 India . 
 
 India .... 
 
 Peru 
 
 Cape of Good Hope 
 
 Cape of Good Hope 
 
130 ANSWERS TO PRACTICAL QUESTIONS 
 
 77. How can you detect the yearly motion of the sun 
 among the stars ? 
 
 (See Astronomy, first note, p. 94.) 
 
 78. Have you actually traced the movement of any one 
 of the planets, so as to understand its peculiar and irregu- 
 lar wandering among the stars ? 
 
 Pupils should be encouraged to watch the various move- 
 ments of the heavenly bodies. Read a thoughtful and sug- 
 gestive article upon Astronomy in High Schools, in Popular 
 Science Monthly, Vol. xx., p. 300. 
 
 79. Hoiv do you explain the varied aspect of the heav- 
 ens in the different seasons of the year ? 
 
 (See Astronomy, p. 92.) 
 
 80. How does the spinning of a top illustrate the sub- 
 ject of precession? 
 
 (See Astronomy, p. 109.) 
 
 81. Why do solar eclipses come on from the west and 
 cross to the east, while lunar eclipses come on from the east 
 and cross to the west ? 
 
 The moon is moving from west to east around the earth. 
 In a solar eclipse, her shadow first strikes the western edge of 
 the sun ; in a lunar eclipse, the eastern edge of the moon first 
 strikes the shadow of the earth. 
 
 The monthly motion of the moon from west to east should 
 be carefully distinguished from the daily motion caused by the 
 earth's rotation. 
 
 82. Newcomb, in his Astronomy, says that, " If, when 
 the inoon is near the meridian, an observer could in a mo- 
 ment jump from New York to Liverpool, keeping his eye 
 fioced upon that body, he could see her apparently jump in 
 the opposite direction about the same distance." Explain. 
 
 This is an illustration of transferred motion. 
 
 83. Wlien, and by whom, was the basis of the calendar 
 we now use fully established ? 
 
 The Koman calendar had become involved in confusion, 
 
IN DESCRIPTIVE ASTRONOMY. 131 
 
 when Julius Caesar, who possessed no little astronomical knowl- 
 edge, called to his assistance a Greek astronomer named Sosig- 
 enes, and adjusted the civil year to the astronomical year. 
 By intercalating the extra day of leap year, he introduced 
 what is known as the Julian Calendar, which is still in use. 
 
 The Persian Calendar, invented in the eleventh century as 
 a correction of the Julian, is remarkable for its accuracy; it 
 consists in making every fourth year bissextile seven times in 
 succession, and making the change for the eighth time in the 
 fifth year instead of the fourth. This is equivalent to reckon- 
 ing the tropical year as SGS^ days, which exceeds the period 
 determined by astronomers only by 0.0001823 of a day, or 
 only | of a second, so that it would require a great number of 
 centuries to displace sensibly the commencement of the civil 
 year. 
 
 The Gregorian Calendar usually employed is somewhat less 
 exact, but it is more easily reduced to days, years, and centu- 
 ries, which is one of the most important objects of a calendar. 
 It consists in employing a bissextile year every fourth year, 
 suppressing three bissextiles in three centuries, and replacing 
 one in the fourth. Thus in every 400 years there are reckoned 
 only 97 leap years, making the length of the year 365^, 
 which exceeds the tropical year by 0.0002581 of a day, or very 
 nearly one second. 
 
 If, following the analogy of the Gregorian Calendar, our 
 successors shall suppress a bissextile every 4,000 years, so as to 
 make 969 instead of 970 leap years in that interval, the length 
 of the year would become 365 9 ^ days, or 365.2422500 days, 
 instead of 365.242219 days, as determined by observation. 
 Haughton's Astronomy. 
 
 84. How much is the Russian reckoning of time be- 
 hind ours ? 
 
 The Russian reckoning is twelve days behind us. 
 
 85. Is there any gain in having the astronomical and 
 the calendar year agree ? 
 
 It is difficult to show what practical object is attained by 
 such coincidence. It is important that summer and winter, 
 
132 ANSWERS TO PRACTICAL QUESTIONS 
 
 seed-time and harvest, shall occur at the same time of the year 
 through several successive generations ; but it is not of the 
 slightest importance that they should occur now at the same 
 time that they did 5,000 years ago. Read Newcomb's As- 
 tronomy, p. 50. 
 
 86. What religious festival is fixed each year by the 
 motion of the moon ? 
 
 Easter occurs on the Sunday after the first full moon fol- 
 lowing the spring equinox. Read article on Easter, in Apple- 
 tons' Cyclopedia. 
 
 87. Wliy can we, at different times, see both poles of 
 the planet Mars ? 
 
 Because the axis of the planet is so much inclined to the 
 plane of the ecliptic. 
 
 88. Wliat famous astronomical discovery was made 
 on the first day of this century ? 
 
 (See Astronomy, p. 155.) 
 
 89. Do the stars rise and set at the poles ? 
 
 (See Astronomy, p. 102.) 
 
 "At one of the poles of the earth, the axis of the earth's 
 rotation would be vertical, and pass through the zenith, and 
 consequently all the celestial objects would appear to travel in 
 horizontal circles, parallel to the horizon, traversing these hori- 
 zontal circles once in 23 hours 56 minutes 4 seconds." 
 
 90. Name and locate the stars of the first magnitude 
 which are seen in our sky. 
 
 The twenty brightest stars in the heavens, or first magni- 
 tude stars, are as follows: they are given in the order of 
 brightness. LOCKYER. 
 
 Sirius, in the constellation Canis Major. 
 
 Canopus, " Argo. 
 
 Alpha, " Centaur. 
 
 Arcturus, " Bootes. 
 
 Rigel, " Orion. 
 
 Capella, " Auriga. 
 
IN DESCRIPTIVE ASTRONOMY. 133 
 
 Vega, in the constellation Lyra. 
 
 Procyon, " Canis Minor. 
 
 Betelgeuse, " Orion. 
 
 Achernar, " Eridanus. 
 
 Aldebaran, " Taurus. 
 
 Beta Centauri, " Centaur. 
 
 Alpha Crucis, " Crux. 
 
 Antares, " Scorpio. 
 
 Altair, " Aquila. 
 
 Spica, " Virgo. 
 
 Fomalhaut, " Piscis Australis. 
 
 Beta Crucis, " Crux. 
 
 Pollux, " Gemini. 
 
 Begulus, " Leo. 
 
 91. Name three bright stars which lie near the first 
 meridian. 
 
 a Andromedae ; y Pegasi ; and j3 Cassiopeiae. 
 
 92. What events ivere transpiring in our history a 
 Saturnian century ago ? 
 
 A Saturnian-year equals 29.45 Earth-years ; a " Saturnian 
 century ago" was, therefore, 2,945 years since, or about 1060 
 B.C. This was about the time of the rise of Tyre, the reign of 
 King David, etc. Read Barnes' General History, p. 79. 
 
 93. What is the sun's declination at the winter solstice ? 
 At the autumnal equinox ? 
 
 (1.) 23| S. (2.) 0. 
 
 94. Will the width of the terrestrial zones always re- 
 main exactly as now ? 
 
 (See Astronomy, p. 111.) 
 
 95. Is it always noon at 12 o'clock ? 
 
 (See Manual, p. 123, Question 21.) 
 
 96. Wlien the sun's declination is 23^ N. 9 in what sign 
 is he then located, and what is his It. A.? 
 
 (See Astronomy, p. 31.) 
 
 This is the time of the summer solstice, and the sun is in 
 Cancer, the fourth sign. 
 
134 ANSWERS TO PRACTICAL QUESTIONS 
 
 97. What is the apparent diameter of the sun ? 
 
 The mean apparent diameter of the sun is 32'. 
 
 98. How can a sailor find Jtis latitude and longitude at 
 
 sea? 
 
 (See Astronomy, p. 280.) 
 
 99. How many miles on the solar disk represent a sec- 
 ond of apparent diameter ? 
 
 V on the solar disk equals 450.3 miles. YOUNG. "The 
 spider-line used in a large telescope will cover a portion of the 
 sun's surface \ of a second in breadth, or hide a strip over 100 
 miles wide." 
 
 100. At what latitude will there be twilight during the 
 entire midsummer night ? 
 
 (See Manual, p. 114, Question 23.) 
 
 "When the sun crosses the meridian at midnight, its distance 
 below the horizon is greater than when the sun is at any other 
 part of its diurnal path. If, therefore, the depression of the 
 sun bellow the horizon at midnight be not greater than 18, the 
 sun will, during the entire night, be within 18 of the horizon, 
 and hence the twilight will be continuous. It will be noticed in 
 solving all the problems connected with twilight (as, for ex- 
 ample, Question 23, p. 114, and Question 27, p. 124), that the 
 result will be slightly changed if the exact amount of the 
 obliquity of the ecliptic (23 27' 15") be used, instead of the 
 ordinary statement, 23|. 
 
 ADDED QUESTIONS AND ANSWERS. 
 
 1. Did Tycho Srahe have a telescope ? 
 
 No. Galileo invented the telescope. 
 
 2. Suppose one should watch the sky, on a winter's 
 evening, from 6 P.M. to 6 A.M., what portion of the celes- 
 tial sphere would he see ? 
 
 All that is ever seen in his latitude. 
 
 3. How do we find tvhat proportion of the sun's heat 
 reaches the earth ? 
 
IN DESCRIPTIVE ASTRONOMY. 135 
 
 Calculate the surface of a sphere whose radius is the dis- 
 tance of the earth from the sun, and then estimate what pro- 
 portion of that area the earth occupies. 
 
 4 . Hoiv do we know the heat of the sun's rays at any 
 planet ? 
 
 The intensity of the heat and light varies inversely as the 
 square of the distance. 
 
 5. Can you give any other proof than that named in 
 the booh of the rotundity of the earth ? 
 
 Aeronauts, when at a proper height, can distinctly see the 
 curving form of the earth's surface. 
 
 6. In what way is the force ivhich acts on a spinning- 
 top opposite to that ivhich produces precession ? 
 
 Gravity, acting on the top, tends to draw C P (Fig. 40) 
 from the perpendicular. The attraction of the sun, acting on 
 the bulging mass of the earth's equator, tends to draw C P 
 toward the perpendicular. 
 
 7. IVIiy is the Tropic of Cancer so called ? 
 
 "When named, the sun was probably in that constellation at 
 the time of the summer solstice. Now, owing to the preces- 
 sion of the equinoxes, the sun is in the constellation G-emini, 
 and to be exact, it should be called the Tropic of Gemini. It 
 is still, however, the sign Cancer, as before. The same reason- 
 ing applies to the Tropic of Capricorn, which is now in the 
 constellation Sagittarius. 
 
 8. In Greenland, at what part of the year will the 
 midnight sun be seen due north ? 
 
 At the summer solstice. 
 
 9. Wlien is the moon seen high in the eastern sJcy in the 
 afternoon, long before the sun sets ? 
 
 During the second quarter before it comes into opposition. 
 
 10. WJiy is the Ecliptic so called ? 
 
 Because eclipses always occur in or near it. 
 
136 EXPLAINING MIRRORS AND LENSES. 
 
 EXPLAINING MIRRORS AND LENSES. 
 
 The author has met with the best success in explaining mir- 
 rors and lenses to his pupils by using the following method : 
 
 A Concave Mirror. Holding up before his eye the fore- 
 finger of each hand, he represents to the pupil how the rays 
 of light enter his eye converging ; how he then sees the object 
 on diverging rays : thus the visual angle being increased, the 
 apparent size of the object is correspondingly increased. By 
 crossing his two forefingers before his eye he represents the 
 focus, and shows how diverging rays then enter the eye ; the 
 object is seen on converging rays, the visual angle is decreased, 
 and the apparent size of the object correspondingly decreased. 
 
 A Convex Mirror. Using the fingers in the same way, he 
 illustrates how diverging rays enter the eye, the object is seen 
 on converging rays, the visual angle is diminished, and the ap- 
 parent size of the object correspondingly diminished. The rays 
 of light are not brought to a focus, hence the second effect of a 
 concave mirror can not be seen. 
 
 The same illustration can be used in explaining lenses, re- 
 membering that the effect of a convex lens is like that of a 
 concave mirror, and of a concave lens that of a convex mirror. 
 
 At the close of the explanation and illustration with the 
 fingers, the following formula is put on the blackboard, and the 
 pupil applies it to each class of mirrors and lenses : 
 
 CONVERGING (diverging) RAYS ENTER THE EYE, THE OBJECT is 
 
 SEEN ON DIVERGING (converging) RAYS ; HENCE THE VISUAL ANGLE 
 
 is INCREASED (decreased), AND THE IMAGE is LARGER (smaller) 
 
 THAN LIFE. 
 
 ASTRONOMY WITH AN OPERA-GLASS. 
 
 In schools where there is no telescope, teachers may find 
 valuable suggestions for class observations in the articles en- 
 titled "Astronomy with an Opera-Glass," by Garrett P. Serviss, 
 in the Popular Science Monthly, April, June, August, and No- 
 vember, 1887, and February, 1888. 
 
TABLE OF THE MINOR PLANETS. 
 
 137 
 
 TABLE OF THE MINOR PLANETS,* 
 
 including alt that have been discovered to date (Oct., 1887). 
 
 ISO. 
 
 NAME. 
 
 DATE OF DISCOVERY. 
 
 DISCOVEKEK. 
 
 1 
 
 Ceres 
 
 1801, January 1 
 
 Piazzi. 
 
 2 
 
 Pallas 
 
 1802, March 28 
 
 Olbers. 
 
 3 
 
 
 1804 Sept 1 
 
 Harding. 
 
 4 
 
 Vesta. 
 
 3 807, March 20 
 
 Olbers. 
 
 5 
 
 
 1845 Dec 8 
 
 Hencke. 
 
 g 
 
 Hebe 
 
 1847 July 1 
 
 Hencke. 
 
 7 
 
 Iris . ... 
 
 1847, August 13 
 
 Hind. 
 
 8 
 9 
 10 
 
 Mora 
 Metis 
 Hygieia 
 
 1847, October 18 
 1848, April 25 
 1849, April 12 
 
 Hind. 
 Graham. 
 Gasparis. 
 
 11 
 12 
 
 Parthenopo 
 
 1850, May 11 
 1850 Sept 13 
 
 Luther. 
 Hind 
 
 13 
 14 
 
 Egeria 
 Irene 
 
 1850, Nov. 2 
 1851 May 19 
 
 Gasparis. 
 Hind 
 
 15 
 
 Eunomia . 
 
 1851 July 29 
 
 Gasparis. 
 
 16 
 
 Psyche 
 
 1852 March 17 
 
 Gasparis. 
 
 17 
 
 Thetis 
 
 1852 April 17 
 
 Ijuther. 
 
 18 
 
 Melpomene 
 
 1852, Juno 24 
 
 Hind. 
 
 19 
 
 Fortuna 
 
 1852 August 22 
 
 Hind. 
 
 20 
 
 Massalia 
 
 1852 Sept 19 
 
 Gasparis. 
 
 21 
 
 Lutetia 
 
 1852, Nov. 15 
 
 Goldschmidt. 
 
 2 
 
 Calliope 
 
 1852 Nov. 16 
 
 Hind. 
 
 23 
 
 Thalia 
 
 1852, Dec. 15 
 
 Hind. 
 
 24 
 
 Themis 
 
 1853, April 5 
 
 Gasparis. 
 
 25 
 
 Phocsea 
 
 1853, April 7 
 
 Chacornac. 
 
 26 
 
 27 
 
 Proserpina 
 
 Euterpe 
 
 1853, May 5 
 1853 Nov. 8 
 
 Luther. 
 Hind. 
 
 28 
 on 
 
 Bellona 
 
 1854, March 1 
 1854 March 1 
 
 Luther. 
 Marth 
 
 30 
 
 Urania. 
 
 1854 July 22 
 
 Hind. 
 
 31 
 
 Euphrosyne 
 
 1854, Sept. 1 
 
 Ferguson. 
 
 32 
 
 Pomona . 
 
 1854 October 26 
 
 Goldschmidt. 
 
 33 
 34 
 
 Polyhymnia 
 Circe. 
 
 1854, October 28 
 1855, April 6 
 
 Chacornac. 
 Chacornac. 
 
 35 
 
 Leucothea 
 
 1855, April 19 
 
 Luther. 
 
 36 
 
 -A-talanta . 
 
 1855, October 5 
 
 Goldschmidt. 
 
 37 
 
 Fides 
 
 1855, October 5 
 
 Luther. 
 
 38 
 
 Leda 
 
 1856, January 12 
 
 Chacornac. 
 
 39 
 
 Leetitia 
 
 1856, February 8 
 
 Chacornac. 
 
 
 
 
 
 * The numerical order is that adopted by the authority of the Berlin 
 Ephemeria. 
 
138 
 
 TABLE OF THE MINOR PLANETS. 
 
 
 NO. 
 
 NAME. 
 
 DATE OF DISCOVERY. 
 
 DISCOVERER. 
 
 40 
 
 Harmonia . . 
 
 1856 March 31 
 
 
 41 
 
 Daphne 
 
 1856 May 22 
 
 
 42 
 
 Isis 
 
 1856 May 23 
 
 
 43 
 
 Ariadne 
 
 1857 April 15 
 
 
 44 
 45 
 
 Nysa 
 Eugenia 
 
 1857, May 27 
 1857 June W 
 
 Q-oldschmidt. 
 
 46 
 
 Hestia. 
 
 1857 August 16 
 
 
 47 
 
 Aglaia. 
 
 1857 Sept 15 
 
 
 48 
 
 Doris. 
 
 1857 Sept 19 
 
 frol c\ ^rOi mi c\t 
 
 49 
 
 Pales 
 
 1857 Sept 19 
 
 fro! rl <^rT"i m i rJ t 
 
 50 
 
 Virginia. 
 
 1857 October 4 
 
 
 51 
 
 Nemausa .. 
 
 1858 January 2 
 
 
 52 
 
 Europa . 
 
 1858 February 4 
 
 Q-oldschniidt 
 
 53 
 
 Calypso 
 
 1858 April 4 
 
 
 54 
 
 Alexandra 
 
 1858 Sept 10 
 
 Q-oldschmidt 
 
 55 
 
 56 
 
 Pandora 
 Melete* 
 
 1858, Sept. 10 
 1857 Sept 9 
 
 Searle. 
 
 57 
 
 Mnemosyne . 
 
 1859 Sept 2 
 
 
 58 
 
 Concordia 
 
 1860 March 4 
 
 
 59 
 
 Elpis 
 
 1860 Sept 1 
 
 
 60 
 
 Echo. . 
 
 1860 Sept 15 
 
 
 61 
 
 Danae. 
 
 1860 Sept 9 
 
 G/oldschmidt 
 
 62 
 
 Erato . 
 
 1860 Sept 14 
 
 
 63 
 
 Ausonia .. 
 
 1861 Feb 10 
 
 Gasparis 
 
 64 
 
 Angelina 
 
 1861 March 4 
 
 Tempel 
 
 65 
 
 Cybele . . . 
 
 1861 March G 
 
 Tempel 
 
 66 
 
 Maia .. 
 
 186 1 April 9 
 
 Tuttle 
 
 67 
 
 Asia. . . . 
 
 1801 April 17 
 
 Pogson 
 
 68 
 
 Leto . 
 
 1861 April 29 
 
 Luther 
 
 69 
 
 
 1861 April 29 
 
 Schiaparelli 
 
 70 
 
 Panopea .. . 
 
 1861 May 5 
 
 G-oldschmidt 
 
 71 
 
 Niobe 
 
 1861 August 13 
 
 Luther. 
 
 72 
 
 Eeronia . 
 
 1861 May 29 
 
 Peters & Safford. 
 
 73 
 
 Clytie 
 
 1862 April 7 
 
 Tuttle. 
 
 74 
 
 Galatea 
 
 1862, August 29 
 
 Tempel. 
 
 75 
 
 Eurydice 
 
 1862 Sept 22 
 
 Peters 
 
 76 
 
 Freia . . 
 
 1862 October 21 
 
 d' Arrest. 
 
 77 
 
 Frisrera 
 
 1862 Nov 12 
 
 Peters. 
 
 78 
 
 Diana ..... 
 
 1863 March 15 
 
 Luther. 
 
 79 
 
 Eurynome 
 
 1863 Sept 14 
 
 "Watson. 
 
 80 
 
 Sappho 
 
 1864 May 2 
 
 Pogson. 
 
 81 
 
 Terpsichore 
 
 1864 Sept 30 
 
 Tempel. 
 
 82 
 
 Alcmene . . 
 
 1864 Nov 27 
 
 Luther. 
 
 
 
 
 
 
 * Goldschmidt at first believed it to be Daphne (41), but Schubert find- 
 ing its period different, called it Pseudo-Daphne. It was not seen from 1857 
 to 1861, when Luther rediscovered it, and named it Melete. 
 
 
TABLE OF THE MINOR PLANETS. 
 
 139 
 
 NO. 
 
 NAME. 
 
 DATE OF DISCOVERY. 
 
 DISOOVEEEK. 
 
 83 
 
 Beatrix 
 
 1865, April 26 
 
 Grasparis 
 
 84 
 85 
 
 Clio 
 lo 
 
 1865, August 26 
 1865 Sept 19 
 
 Luther. 
 Peters 
 
 86 
 
 
 1866, January 4 
 
 Tietjen 
 
 87 
 
 Sylvia 
 
 1866 May 16 
 
 
 88 
 
 Thisbe 
 
 1866 June 15 
 
 Peters 
 
 89 
 
 
 1866 August 6 
 
 Stephan 
 
 90 
 
 Antiope 
 
 1866, October 11 
 
 Luther. 
 
 91 
 
 JEgina 
 
 1866, Nov. 4 
 
 Stephan. 
 
 92 
 
 Undina 
 
 1867, July 7 
 
 Peters. 
 
 93 
 
 Minerva 
 
 1867, August 24 
 
 Watson. 
 
 94 
 
 Aurora 
 
 1867, Sept. 6 
 
 Watson. 
 
 95 
 
 Arethusa 
 
 1867, Nov. 23 
 
 Luther. 
 
 96 
 
 ^?Egle 
 
 1 868, February 17 
 
 Coggia . 
 
 97 
 98 
 
 Clotho 
 lanthe 
 
 1868, February 17 
 1868, April 18 
 
 Tempel. 
 Peters. 
 
 99 
 
 Dike 
 
 1868, May 28 
 
 Borelly 
 
 100 
 
 Hecate .. 
 
 1868, July 11 
 
 Watson. 
 
 101 
 
 Helena 
 
 1868, August 15 
 
 "Watson. 
 
 102 
 
 Miriam 
 
 1868, August 22 
 
 Peters. 
 
 103 
 
 Hera 
 
 1868, Sept. 7 
 
 Watson. 
 
 104 
 
 Clymene . 
 
 1868, Sept. 13 
 
 Watson. 
 
 105 
 
 Artemis 
 
 1868, Sept. 16 
 
 Watson. 
 
 106 
 
 Dione . . 
 
 1868, October 10 
 
 Watson. 
 
 107 
 
 Camilla 
 
 1868, Nov. 17 
 
 Pogson . 
 
 108 
 
 
 1869, April 2 
 
 Luther. 
 
 109 
 
 Felicitas 
 
 1869, October 9 
 
 Peters. 
 
 110 
 
 Lydia 
 
 1870, April 19 
 
 Borelly. 
 
 111 
 
 Ate 
 
 1870, August 14 
 
 Peters. 
 
 112 
 
 Iphigenia 
 
 1870, Sept. 19 
 
 Peters. 
 
 113 
 
 Amalthea. 
 
 1871, March 12 
 
 Luther. 
 
 114 
 
 Cassandra ... 
 
 1871, July 23 
 
 Peters. 
 
 115 
 
 Thyra 
 
 1871, August 6 
 
 Watson. 
 
 116 
 
 Sirona. 
 
 1871, Sept. 8 
 
 Peters. 
 
 117 
 
 Lomia. 
 
 1871, Sept 13 
 
 Borelly. 
 
 118 
 
 Peitho . 
 
 1872, March 15 
 
 Luther. 
 
 119 
 
 Althsea 
 
 1872, April S 
 
 Watson. 
 
 120 
 
 Lachesis 
 
 1872, April 10 
 
 Borelly. 
 
 121 
 
 Hermione 
 
 1872 May 12 
 
 Watson 
 
 122 
 
 Gerda . 
 
 1872 July 31 
 
 Peters 
 
 123 
 
 Brunhilda . 
 
 1872 July 31 
 
 Peters. 
 
 124 
 
 Alceste 
 
 1872 August 23 
 
 Peters. 
 
 125 
 
 Liberatrix . 
 
 1872 Sept 11 
 
 Prosper Henry. 
 
 126 
 
 Velleda 
 
 1872 Nov. 5 
 
 Paul Henry. 
 
 127 
 
 Johanna . 
 
 1872 Nov. 5 
 
 Prosper Henry. 
 
 128 
 
 Nemesis. 
 
 1872 Nov 25 
 
 Watson. 
 
 129 
 
 Antigone.. 
 
 1873 February 5 
 
 Peters. 
 
 130 
 
 Electra,... . . 
 
 1873, February 17 
 
 Peters. 
 
 
 
 
 
140 
 
 TABLE OF THE MINOR PLANETS. 
 
 NO. 
 
 NAME. 
 
 DATE OF DISCOVERY. 
 
 DISCOVERER. 
 
 131 
 
 "Vala . . . 
 
 1873 May 26 
 
 Peters. 
 
 132 
 
 .^Ethra 
 
 1873 June 13 
 
 "Watson. 
 
 133 
 
 Gyrene 
 
 1873 August 16 
 
 "Watson. 
 
 134 
 
 Sophrosyne 
 
 1873, Sept. 27 
 
 Liuther. 
 
 135 
 
 Hertha . . 
 
 1874 Feb 18 
 
 Peters. 
 
 130 
 
 Austria. 
 
 1874 March 18 
 
 Palisa. 
 
 137 
 
 Melibcea 
 
 1874 April 21 
 
 Palisa. 
 
 138 
 
 Tolosa . 
 
 1874 May 19 
 
 Perrotin. 
 
 139 
 
 Juewa 
 
 1874 October 10 
 
 Watson. 
 
 140 
 
 Siwa 
 
 1874 October 13 
 
 Palisa. 
 
 141 
 
 Lumen 
 
 1875 January 13 
 
 Paul Henry. 
 
 142 
 
 Polana. 
 
 1875, January 28 
 
 Palisa. 
 
 143 
 
 Adria . 
 
 1875, Feb. 23 
 
 Palisa. 
 
 144 
 
 "Vibilia . . 
 
 1875, June 3 
 
 Peters. 
 
 145 
 
 Adeona .... 
 
 1875, June 3 
 
 Peters. 
 
 146 
 
 Lucina ... 
 
 1875, Juno 
 
 Borelly. 
 
 147 
 
 Protogeneia .... 
 
 1875, July 11 
 
 Schulhof. 
 
 148 
 
 Gallia 
 
 1875, August 7 
 
 Prosper Henry. 
 
 149 
 
 Medusa 
 
 1875, Sept. 21 
 
 Perrotin. 
 
 150 
 
 Nuwa 
 
 1875, October 18 
 
 "Watson. 
 
 151 
 152 
 
 Abundantia 
 Atala 
 
 1875, Nov. 1 
 1875, Nov. 2 
 
 Palisa. 
 Paul Henry. 
 
 153 
 
 Hilda 
 
 1875 Nov 2 
 
 Palisa 
 
 154 
 
 Bertha 
 
 1875 Nov A 
 
 Prosper Henry 
 
 155 
 156 
 157 
 
 Scylla 
 Xantippo 
 Dejanira 
 
 1875, Nov. 
 1875, Nov. 22 
 1875, Dec. 1 
 
 Palisa. 
 Palisa. 
 Borelly. 
 
 158 
 
 
 1876 January 4 
 
 Knorre. 
 
 159 
 160 
 
 Emilia 
 "Una 
 
 1876, January 26 
 1870, February 20 
 
 Paul Henry. 
 Peters. 
 
 161 
 
 
 1876 April 18 
 
 "Watson 
 
 162 
 
 Laurentia 
 
 187G, April 21 
 
 Prosper Henry. 
 
 163 
 
 
 1876, April 26 
 
 Perrotin. 
 
 164 
 
 Eva 
 
 1876 July 12 
 
 Paul Henry. 
 
 165 
 
 Hioreley 
 
 1876, August 
 
 Peters. 
 
 166 
 
 Uhodopo 
 
 1876, August 15 
 
 Peters. 
 
 167 
 
 Urda 
 
 1876 August 28 
 
 Peters. 
 
 168 
 
 Sibylla 
 
 1876, Sept. 28 
 
 Watson. 
 
 169 
 
 Zelia 
 
 1870, Sept. 28 
 
 Prosper Henry. 
 
 170 
 
 
 1877 January 10 
 
 Perrotin. 
 
 171 
 
 Ophelia 
 
 1877, January 13 
 
 Borelly. 
 
 172 
 173 
 
 Bancis 
 Ino 
 
 1877, February 5 
 1877, August 2 
 
 Borelly. 
 Borelly. 
 
 174 
 175 
 176 
 
 Phaedra 
 Andromache 
 Idunna 
 
 1877, Sept. 3 
 1877, October 1 
 1877, October 14 
 
 "Watson. 
 Watson. 
 Peters. 
 
 177 
 178 
 
 Irma 
 Belisana 
 
 1877, Nov. 5 
 1877 Nov 6 
 
 Prosper Henry. 
 Palisa. 
 
 179 
 
 Clytemnestra 
 
 1877, Nov. 12 
 
 Watson. 
 
 
 
 
 
TABLE OF THE MINOR PLANETS. 
 
 141 
 
 NO. 
 
 HAME. 
 
 DATE OF DISCOVERT. 
 
 DISCOVERER. 
 
 180 
 
 
 1878, January 29 
 
 Perrotin 
 
 181 
 
 Eucharis 
 
 1878, February 2 
 
 Cottenot 
 
 182 
 
 Elsa 
 
 1878 February 7 
 
 Palisa 
 
 183 
 
 Istria 
 
 1878, February 8 
 
 Palisa 
 
 184 
 
 Deiopeia 
 
 1878 February 28 
 
 Palisa 
 
 185 
 
 Eunike 
 
 1878 March 1 
 
 Peters 
 
 186 
 
 Celuta 
 
 1878, April 6 
 
 Prosper Henry 
 
 187 
 188 
 
 Lamberta 
 Menippe. 
 
 1878, April 11 
 1878 June 18 
 
 Coggia. 
 Peters 
 
 189 
 
 Ph.th.ia 
 
 1878 Sept 9 
 
 Peters. 
 
 190 
 
 Ismene 
 
 1878 Sept 22 
 
 Peters 
 
 191 
 
 Kolga 
 
 1878 Sept 30 
 
 Peters 
 
 192 
 193 
 194 
 
 Nansicaa 
 Ambrosia 
 Procne 
 
 1879, February 17 
 1879, February 28 
 1879 March 21 
 
 Palisa. 
 Coggia. 
 Peters 
 
 195 
 
 Eurycleia. ... 
 
 1879 April 22 
 
 Palisa 
 
 196 
 
 Philomela. 
 
 1879 May 17 
 
 Peters 
 
 197 
 
 Arete... 
 
 1879 May 21 
 
 Palisa 
 
 198 
 
 -A_mpella 
 
 1879 June 13 
 
 Borelly 
 
 199 
 
 Byblis 
 
 1879 July 9 
 
 Peters 
 
 200 
 
 Dynamene 
 
 1879 July 27 
 
 Peters 
 
 201 
 
 
 1879 August 7 
 
 Palisa 
 
 202 
 203 
 
 Chryseis 
 Pompeia 
 
 1879, Sept. 11 
 1879, Sept. 25 
 
 Peters. 
 Peters 
 
 204 
 205 
 206 
 
 Callisto 
 Martha 
 Hersilia 
 
 1879, October 8 
 1879, October 13 
 1879 October 13 
 
 Palisa. 
 Palisa. 
 Peters 
 
 207 
 
 Hedda 
 
 1879 October 17 
 
 Palisa 
 
 208 
 
 Lacrymosa . 
 
 1879 October 21 
 
 Palisa 
 
 209 
 
 Dido 
 
 1879 October 22 
 
 Peters 
 
 210 
 
 Isabella 
 
 1879, Nov 12 
 
 Palisa 
 
 211 
 
 Isolda 
 
 1879, Dec 10 
 
 Palisa 
 
 212 
 
 Medea.... 
 
 1880 February G 
 
 Palisa 
 
 213 
 
 Ldlisea 
 
 1880 February 16 
 
 Peters 
 
 214 
 
 Aschera 
 
 1880 March 1 
 
 Palisa 
 
 215 
 
 CEnone 
 
 1880 April 7 
 
 
 216 
 217 
 218 
 219 
 
 Cleopatra ... 
 Eudora 
 Bianca 
 Thusnelda 
 
 1880, April 10 
 1880, August 30 
 1880, Sept. 4 
 1880, Sept. 30 
 
 Palisa. 
 Coggia. 
 Palisa. 
 Palisa 
 
 220 
 
 Stephania 
 
 1881 May 20 
 
 Palisa 
 
 221 
 
 Eos 
 
 188^ January 18 
 
 Palisa. 
 
 222 
 223 
 
 Lucia 
 Uosa 
 
 1882, February 9 
 1882, March 9 
 
 Palisa. 
 Palisa. 
 
 224 
 
 Oceana 
 
 1882 March 30 
 
 Palisa. 
 
 225 
 
 Henrietta 
 
 1882, April 19 
 
 Palisa. 
 
 226 
 
 "Weringia. 
 
 1882 July 19 
 
 Palisa. 
 
 227 
 228 
 
 Philosophia 
 Agathe . . . 
 
 1882*, August 12 
 1882, August 19 
 
 Paul Henry. 
 Palisa. 
 
 
 
 
 
142 
 
 TABLE OF THE MINOR PLANETS. 
 
 NO. 
 
 NAME. 
 
 DATE OF DISCOVERY. 
 
 DISCOVEBEB. 
 
 229 
 
 Adelinda . 
 
 1882 August 22 
 
 Palisa 
 
 230 
 
 Athamantis. . 
 
 1882 Sept 3 
 
 De Ball 
 
 231 
 
 "Vindobona 
 
 1882 Sept 10 
 
 Palisa 
 
 232 
 
 Russia 
 
 1883 January 31 
 
 Palisa 
 
 233 
 
 Asterope 
 
 1883 May 11 
 
 Borelly 
 
 234 
 
 Barbara 
 
 1883 August 13 
 
 Peters. 
 
 235 
 
 Caroline 
 
 1883 Nov 29 
 
 Palisa. 
 
 236 
 
 Honoria 
 
 1884 April 26 
 
 Palisa. 
 
 237 
 
 Coelestina . 
 
 1884 June 27 
 
 Palisa 
 
 238 
 
 
 1884 July 1 
 
 Knorre 
 
 239 
 
 Adrastea 
 
 1884 August 18 
 
 Palisa. 
 
 240 
 
 "Vanadis 
 
 1884 August 27 
 
 Borelly. 
 
 241 
 
 G/ermania 
 
 1884 Sept 12 
 
 Luther. 
 
 242 
 
 Kriemhild. . .. 
 
 1884 Sept 2 
 
 Palisa 
 
 040 
 
 Ida 
 
 1884 Sept 20 
 
 Palisa 
 
 244 
 
 Sita 
 
 1884 October 14 
 
 Palisa. 
 
 245 
 
 Vera 
 
 1885 February G 
 
 Poison 
 
 246 
 
 Asporina .... .... 
 
 1885 March 
 
 Borelly 
 
 247 
 
 Eukrate . . . 
 
 1885 March 14 
 
 Luther 
 
 248 
 
 Tjiii i iciji 
 
 1885 June 5 
 
 Palisa 
 
 249 
 
 Use 
 
 1885 August 17 
 
 Peters 
 
 250 
 
 Bettina 
 
 1885 Sept 3 
 
 Palisa 
 
 251 
 
 Sophia 
 
 1885 October 4 
 
 Palisa 
 
 Of>Q 
 
 
 1885 October 27 
 
 
 253 
 
 OCA 
 
 Mathilda 
 
 1885, Nov. 12 
 1886 March 31 
 
 Palisa. 
 Palisa 
 
 255 
 
 Oppavia 
 
 1886 March 31 
 
 Palisa. 
 
 0-f 
 
 
 1886 April 3 
 
 Palisa 
 
 257 
 
 Silesia 
 
 1886 April 5 
 
 Palisa. 
 
 258 
 
 Tyche 
 
 1886 May 4 
 
 Luther. 
 
 259 
 
 Altheia 
 
 1886 June 28 
 
 Peters. 
 
 260 
 
 Huberta 
 
 1886 October 3 
 
 Palisa. 
 
 261 
 
 
 1886 October 31 
 
 Peters. 
 
 262 
 
 Valda 
 
 1886 Nov 3 
 
 Palisa. 
 
 263 
 
 Dresda . 
 
 1886 Nov. 3 
 
 Palisa. 
 
 264 
 
 Libussa 
 
 1886, Dec. 17 
 
 Peters. 
 
 265 
 
 Anna . 
 
 1887, February 25 
 
 Palisa. 
 
 266 
 
 Aline 
 
 1887, May 17 
 
 Palisa. 
 
 267 
 
 Tirza . . 
 
 1887, May 27 
 
 Charlois. 
 
 268 
 
 
 1887, June 9 
 
 Borelly. 
 
 269 
 
 
 1887, Sept. 21 
 
 Palisa. 
 
 270 
 
 
 1887, October 8 
 
 Peters. 
 
 271 
 
 
 1887, October 16 
 
 Knorre. 
 
 
 
 
 
 Prom this Table, it will be observed that, next to Palisa, of Vienna, 
 Austria, the one investigator who has discovered the largest number of 
 asteroids is our own Dr. Peters, of Clinton, N. Y. It is probable that all 
 the larger asteroids have now been identified. 
 
ANSWERS 
 
 TO THE 
 
 QUESTIONS 
 
 IN THE 
 
 HYGIENIC PHYSIOLOGY. 
 
 23 ! Why does not a fall hurt a child as much as it 
 does a grown person ? 
 
 The bones of a child are largely cartilaginous, and so do not 
 transmit a shock, or readily yield to a blow. They are also well 
 padded with fat. 
 
 2. Should a young child ever be urged to stand or 
 walk? 
 
 No ; bow-legs are often caused by the premature use of the 
 lower limbs in standing or walking. Nature is the best guide 
 in such matters. 
 
 3. What is meant by " breaking one's neck " ? 
 
 The dislocation of the vertebrae and consequent injury of 
 the spinal cord. 
 
 4. Should chairs or benches have straight backs ? 
 
 The backs should conform to the natural shape of the spine. 
 This tends to prevent curvatures and other distortions of the 
 vertebral column. 
 
 5. Should a child's feet be allowed to dangle from a 
 high seat ? 
 
 The position is as unnatural and painful for a child as for a 
 grown person. 
 
 6. Why can ^ve tett whether a fowl is young by pressing 
 on the point of the breast-bone ? 
 
144 ANSWERS TO PRACTICAL QUESTIONS 
 
 Because that part of the breast-bone is not ossified in a 
 young fowl. 
 
 7. What is the use of the marrow in the bones ? 
 
 It contains the blood-vessels carrying material for the growth 
 of the bone, and also diffuses any shock which the bone may 
 receive. 
 
 8. Why is the shoulder so often put out of joint ? 
 
 Because of the shallowness of the socket in the scapula. 
 f>. Hoiv can you tie a knot in a bone ? 
 
 By removing the mineral matter, and thus softening a rib- 
 bone, a knot can be easily tied in it. 
 
 10. Why are high, pillows injurious ? 
 
 They elevate the head, and so give an unnatural position to 
 the spine. For the pads between the vertebrae to assume their 
 proper shape during the night they should be relieved of all 
 pressure. 
 
 11. Is a stooping posture a healthy position ? 
 
 No. Such a posture, made habitual, contracts the chest, 
 changes the outline of the spine, and diminishes the vitality 
 of the system. 
 
 12. Ought a boot to have a heel-piece ? 
 
 A low and broad heel-piece probably aids in walking ; a 
 narrow or high one weakens and enlarges the ankle, produces 
 bunions, corns, etc., by throwing the weight forward upon the 
 toes, and makes the gait exceedingly ungraceful. 
 
 13. Why should one always sit and walk erect ? 
 
 Because then all the organs are in their natural position. 
 An erect carriage is as conducive to health as to beauty. 
 
 14. Why does a young child creep rather than walk ? 
 
 (See Physiology, p. 50.) 
 
 Its bones not yet being fully ossified, nature teaches it not 
 to bear its weight upon them. Besides, it has not yet learned 
 the difficult art of balancing itself. 
 
IN HYGIENIC PHYSIOLOGY. 145 
 
 15. What is the natural direction of the big toe ? 
 
 The natural direction of the big toe is in a line with the 
 long axis of the foot, but the conventional boot, which insists 
 upon an even-sided symmetry, and often upon a narrow tip, 
 tends to crowd the extremity of this toe toward the middle line 
 of the sole. If well-developed feet are placed side by side and 
 heel to heel, the two great toes will be found to be parallel to 
 each other, and to touch each other almost to their very ends. 
 If the same feet, clad in the shoes of the period, are placed in 
 the same position, it will be found that, while the heels are in 
 contact, the tips of the two great toes will be considerably 
 separated. 
 
 16. IVTiat is the difference between a sprain and a 
 fracture ? A dislocation ? 
 
 In a sprain, the ligaments which bind the bones of a joint 
 are strained, twisted, or torn from their attachments ; in a 
 fracture, the bone itself is broken ; in a dislocation, the bone is 
 displaced from its socket. 
 
 17. Does the general health of the system affect the 
 strength of the bones ? 
 
 Certainly. Impoverished blood will not make healthy bone. 
 
 46 1. IVliat class of lever is the foot ivhen ive lift a 
 iveiglit on the toes ? 
 
 The third class. The ankle-joint is the fulcrum, the weight 
 is at the toes, and the power is in front of the ankle, where 
 the muscle which lifts the toes (the extensor digitorium) is at- 
 tached to the foot. 
 
 2. Explain the movement of the body baclwvard and 
 forward, ^vhen resting upon the tfiigh-botie as a ful- 
 crum. 
 
 The weight is at the center of gravity of the head and 
 trunk, high above the hip-joints, where the fulcrum is situated. 
 The flexor muscles of the thigh are the power, and act close to 
 the fulcrum. The weight is sometimes directly over the ful- 
 crum, and may be on any side of it. This seems to the author 
 
146 ANSWESS TO PRACTICAL QUESTIONS 
 
 to be an example of the first or second class of lever. Huxley 
 gives it as an illustration of the third class. 
 
 3. What class of lever do ive use wJien we lift the foot 
 while sitting down ? 
 
 The third class. The fulcrum is the knee-joint ; the weight 
 is at the center of gravity of the foot and leg, and the power 
 is applied by the ligament which passes over the patella. 
 
 4. Explain the swing of the arm from the shoulder. 
 
 (See Physiology, p. 34 ) 
 
 The third class. The fulcrum is the shoulder- joint ; the 
 weight is at the center of gravity of the arm and hand, and 
 the power is applied by the biceps or triceps muscle at its at- 
 tachment near the elbow. 
 
 5. What class of lever is used in betiding our fingers ? 
 
 The fulcrum is at the junction of the finger with the palm ; 
 the weight is at the center of gravity of the finger, and may 
 play about the fulcrum as stated in second question. It is the 
 third class of lever, especially when force is exerted at the ex- 
 tremity of the fingers. 
 
 6. What class of lever is our foot when we tap the 
 ground with our toes ? 
 
 (See Physiology, Fig. 14, Tc.) 
 
 The first class. The weight is at the toe when the force is 
 exerted ; the fulcrum is at the ankle ; and the power is applied 
 by the gastrocnemius muscle at its attachment to the heel. 
 
 7. Wliat class of lever do we use when we raise our- 
 selves from a stooping position ? 
 
 The third class. See second question. If we are attempt- 
 ing to lift a heavy burden, the bones act on the principle of 
 the toggle-joint. "When one stoops to take a heavy weight 
 upon his back or shoulder, he puts both the knee and the hip- 
 joints into the condition that the toggle-joint is when it is bent; 
 and then, as he straightens up, the weight is raised by an ac- 
 tion of the joints precisely similar to that of the toggle-joint in 
 machinery. In the case of the knee, the straightening of the 
 
IN HYGIENIC PHYSIOLOGY. 147 
 
 joints is done by the muscles on the front part of the thigh, 
 that draw up the knee-pan with the tendon attached to it. 
 This is using the principle of the toggle-joint in pressing up- 
 ward. It is also sometimes used in pressing downward. In 
 crushing any thing with the heel, we give great force to the 
 blow on the principle of the toggle-joint, by flexing the knee 
 and straightening the limb as we bring down the heel upon the 
 thing to be crushed. In pushing any thing before us, we bend 
 the elbow as preparatory to the act, and then thrust the arm 
 out straight, thus exemplifying the toggle-joint. The horse 
 gives great force to his kick in the same way. The great 
 power exerted by beasts of draught and burden is to be re- 
 ferred very much to the principle of the toggle-joint. When a 
 horse is to draw a heavy load, he bends all his limbs, especially 
 the hinder ones, and then as he straightens them, he starts the 
 load. In this case the ground is the fixed block of the mechan- 
 ism, the body of the horse to which the load is attached is the 
 movable one, and his limbs are so many toggle-joints. By this 
 application of the principle, we see draught horses move very 
 heavy loads." HOOKER'S Physiology. "So (admitting fable to be 
 fact), when the farmer, in answer to his petition for assistance, 
 was commanded by Hercules to exert himself to raise his wagon 
 from the pit, he placed his shoulder against the wheel, and 
 drawing his body up into a crouching attitude, whereby all his 
 joints are flexed, and making his feet the fixed points, by a 
 powerful muscular effort, he straightened the toggle-joints of 
 his limbs, and the wheel was raised from its bed of miry clay. 
 His horses at the same moment extending their joints, the 
 heavily laden wagon was carried beyond the reach of further 
 detention. " G-BISCOM. 
 
 8. What class of lever is the foot when we walk ? 
 
 In the first stage it is clearly the second class. (See Physi- 
 ology, Fig. 18.) The fulcrum is the ground on which the toes 
 rest ; the power is applied by the gastrocnemius muscle (see 
 Fig. 14, ft) to the heel ; the resistance is so much of the weight 
 of the body as is borne by the ankle-joint of the foot, which of 
 course lies between the heel and the toes. 
 
148 ANSWERS TO PRACTICAL QUESTIONS 
 
 9. Why can we raise a heavier iveight with our hand 
 when liftinrj with the elbow than from the shoulder? 
 
 Because we bring the fulcrum .nearer the power. In the 
 former case it is at the elbow ; in the latter, at the shoulder. 
 
 10. Wliat class of lever do ^ve employ when ive are hop- 
 ping, the thigh-bone being bent up toward the body and 
 not used ? 
 
 In this case the fulcrum is at the hip-joint. The power 
 (which may be assumed to be furnished by the rectus muscle* 
 of the front of the thigh) acts upon the knee-cap ; and the po- 
 sition of the weight is represented by that of the center of 
 gravity of the thigh and leg, which will lie somewhere between 
 the end of the knee and the hip. HUXLEY. 
 
 11. Describe the motions of the bones when we are 
 using a gimlet. 
 
 The radius rolls on the ulna at the elbow, while the ulna 
 rolls on the radius at the wrist. The two combined produce a 
 free, rotary motion. 
 
 12. Wliy do we tire when we stand erect ? 
 
 (See Physiology, p. 37.) 
 
 Because so large a number of muscles must be in constant 
 action to maintain this position. 
 
 13. Why does it rest us to change our work ? 
 
 "We thereby bring into use a new set of muscles. 
 
 14. !V7iy and when is dancing a beneficial exercise? 
 
 When dancing is performed out-of-doors, or in a well-ven- 
 tilated room, and at proper hours, it is doubtless a beneficial 
 exercise, since it employs the muscles and pleasantly occupies 
 the mind. Late at night, in a heated room, with thin clothing 
 and exciting surroundings, it is simply a dangerous dissipation, 
 ruinous to the health, alike of body and soul. 
 
 * This muscle is attached above to the haunch-bone or ileum, and be- 
 low to the knee-cap. The latter bone is connected by a strong ligament 
 with the tWa. 
 
IN HYGIENIC PHYSIOLOGY. 149 
 
 15. Why can ive exert greater force with the back teeth 
 than with the front ones ? 
 
 (See Physiology, p. 35.) 
 
 The lower jaw is a lever of the second class. In the former 
 case the resistance to be overcome, i.e., the weight, is situated 
 much nearer the power. 
 
 16. Wliy do ive lean forward ivhen ive wish to rise from 
 
 a chair ? 
 
 (See Popular Physics, p. 57.) 
 
 In order to bring the center of gravity over the feet. 
 
 17' IVliy does the projection of the heel-bone make 
 ivalkiiig easier ? 
 
 (See Frontispiece, and also Fig. 18 in Physiology.) 
 It brings the power further from the fulcrum or weight. 
 
 18. Does a horse travel ivith less fatigue over aflat than 
 a hilly country ? 
 
 No. The variety of travel in a hilly country, other things 
 being equal, tends to rest the horse, and enable him to better 
 endure the fatigue of the journey. 
 
 19. Can you move your upper jaw ? 
 
 All the bones of the face, except the lower jaw, are firmly 
 and immovably articulated with one another and with the cra- 
 nium. LEIDY. 
 
 20. Are people naturally right or left-handed ? 
 
 Many persons are naturally either right or left-handed ; but 
 most can and should learn to use either hand with equal 
 facility. 
 
 21. Why can so few persons move their ears by the 
 muscles ? 
 
 Perhaps because of lack of practice ; more probably, how- 
 ever, the muscles (see Physiology, p. 53 and Fig. 14) are de- 
 veloped in few persons. 
 
 22. Is the blacksmith's right arm healthier than the 
 left? 
 
150 ANSWERS TO PRACTICAL QUESTIONS 
 
 By no means. Strength is not essential to health. The 
 right arm may be stronger, but the functions of the left may 
 be as active and well-performed. 
 
 23. Soys often, though foolishly, thrust a pin into the 
 flesh just above the knee. Why is it not painful ? 
 
 The muscles of the leg there end in tendons, which are in- 
 sensible. 
 
 24. Will ten minutes 9 practice in a gymnasium answer 
 for a day's exercise ? 
 
 Spasmodic or violent exercise is not beneficial. It should be 
 comparatively quiet, gentle, and continuous to produce the best 
 effect. Moreover, the vitalizing influences of the sun and pure 
 air demand that we should exercise out-of-doors. 
 
 25. Why would an elastic tendon be unfitted to trans- 
 mit the motion of a muscle ? 
 
 Force would be lost by its transmission through an elastic 
 medium. 
 
 26. IVlien one is struck violently on the head, why does 
 he instantly fall ? 
 
 The body is kept erect only by the constant exercise of 
 many muscles. These perform their functions through the un- 
 conscious action of the brain and spinal cord. A blow para- 
 lyzes the nervous system, the muscles at once cease to act, and 
 the body falls by its weight. 
 
 27 What is the cause of the difference between light 
 and dark meat in a fowl ? 
 
 The amount of blood which circulates through different 
 parts of the body. The organs of a fowl which are used the 
 most become the darkest. 
 
 69 1. If a hair be plucked out, will another grotv in 
 its place ? 
 
 Yes. A new hair will always grow out so long as the pa- 
 pilla at the bottom of the follicle remains uninjured. 
 
IN HYGIENIC PHYSIOLOGY. 151 
 
 2. Wliat causes the hair to i( stand on end" when we 
 
 are frightened ? 
 
 (See Physiology, p. 53.) 
 
 Many of the unstriated muscular fibers from the true skin 
 pass obliquely down from the surface of the dermis to the 
 under side of the slanting hair-follicles. The contraction of 
 these fibers erects the hairs, and by drawing the follicles to the 
 surface and drawing in a little point of the skin, produces that 
 roughness of the integument called "goose-skin," or Cutis Anser- 
 ina. The standing on end of the hair of the head, as the re- 
 sult of extreme fright, may be partly due to the contraction of 
 such fibers, as well as to the action of the occipito-frontalis 
 muscle. CUTTER. 
 
 3. Why is the skin roughened by riding in the cold ? 
 
 (See Physiology, p. 53 ; also Answer to Q uestion 2.) 
 
 4. Why is the back of a washer-woman's hand less 
 water-soaked than the palm? 
 
 The difference depends upon the relative abundance of the 
 oil-glands in different parts of the body. 
 
 5. WJiat would be the length of the perspiratory tubes 
 in a single square inch of the palm, if placed end to end ? 
 
 (See Physiology, p. 61.) 
 
 The length of the perspiratory tubes differs not only in dif- 
 ferent persons but in different parts of the same body. Some 
 authorities estimate the average length at \ of an inch, while 
 others and, generally, later authorities give only -^ of an inch. 
 If we assume the former measurement, we have : 2,800 x in. 
 = 21^00 i n . = 58 ft. 4 in. If the latter, we have 2,800x T V in. 
 = Af$a in. = 14 ft. 7 in. 
 
 6. JVTiat colored clothing is best adapted to all seasons ? 
 
 (See Physiology, p. 67 ; Popular Physics, p. 260.) 
 
 Light-colored clothing is cooler in summer and warmer in 
 winter. 
 
 7. What is the effect of paint and powder on the skin ? 
 
 (See Physiology, p. 62.) 
 
152 ANSWERS TO PRACTICAL QUESTIONS 
 
 They fill the pores of the skin, and thus prevent the pas- 
 sage of the perspiration. Moreover, they often contain sub- 
 stances which are poisonous, and being carried in by the absorb- 
 ents cause disease. 
 
 8. Is water-proof clothing healthful for constant wear ? 
 
 No. It retains the insensible perspiration by which waste 
 matter is being constantly thrown off from the system. 
 
 9. Why are rubbers cold to the feet ? 
 
 They retain the insensible perspiration. The moisture which 
 gathers absorbs the heat of the feet, and readily conducts it 
 from the body. 
 
 10. Why does the heat seem oppressive ivhen the air is 
 moist ? 
 
 In the moisture-laden atmosphere, the evaporation of the 
 insensible perspiration from the surface of the body goes on 
 slowly. The heat, which would otherwise pass off through the 
 pores, is retained in the system. 
 
 11. Why is friction of the skin invigorating after a 
 cold bath ? 
 
 (See Physiology, p. 64, 65.) 
 
 The friction produces heat, expands the veins, etc., on the 
 surface, and, calling the blood in that direction, produces a 
 vigorous circulation. In other words, it causes a reaction.* 
 
 * Strength in the living body is maintained by the full but natural 
 exercise of each organ ; and, as we have seen, the actions of these por- 
 tions of the nervous system is made dependent upon influences conveyed 
 to them by the sensitive nerves distributed over the various parts of the 
 body. And among these the nerves passing to the skin are the chief. The 
 full access of all healthful stimuli to the surface, and its freedom from all 
 that irritates or impedes its functions, are the first external conditions of 
 the normal vigor of this nervous circle. Among these stimuli, fresh air 
 and pure water hold the first place. Sufficient warmth is second. The 
 great and even wonderful advantages of cleanliness are partly referable to 
 the direct influence of a skin healthily active, open to all the natural 
 stimuli, and free from morbid irritation, upon the nerve-centers of which 
 it is the appointed excitant. This influence is altogether distinct from 
 those cleansing functions which the healthy skin performs for the blood ; 
 and in any just estimate of its value is far too important to be over- 
 looked. HINTOJT. 
 
IN HYGIENIC PHYSIOLOGY. 153 
 
 12. Why does the hair of domestic animals become 
 roughened in ivinter ? 
 
 (See Question 2.) 
 
 It is a wise provision of Nature, since more air a non-con- 
 ductor of heat is retained by the hair, and thus the rough 
 winter-coat of an animal is warmer than its smooth summer- 
 coat. 
 
 13. Why do fotvls spread their feathers before they 
 
 perch for the night ? 
 
 (See Question 12.) 
 
 This is the same wise provision of Nature to protect the 
 fowl against the chilliness of the night. More air is confined 
 by the roughened feathers, and thus the internal heat of the 
 bird is prevented from radiating. 
 
 14. Hoiv can an extensive burn cause death by conges- 
 tion of the lungs ? 
 
 (See Physiology, p. 63.) 
 
 The insensible perspiration is stopped upon the burned sur- 
 face, and the excretions are sent to the lungs, which are over- 
 worked and overloaded by the excess. 
 
 15. Why do ive perspire so profusely after drinking cold 
 water ? 
 
 The vital organs being chilled for an instant, the blood is 
 sent to the surface, a reaction is produced, the skin acts more 
 vigorously as an excretory organ, and the insensible perspira- 
 tion is thrown off more rapidly. 
 
 16. What are the best means of preventing skin dis- 
 eases, colds, and rheumatism ? 
 
 The skin should be kept in a healthy state by bathing, rub- 
 bing, etc. Exposure to sudden changes of temperature should 
 be avoided as far as possible. Flannel worn next the skin, in 
 all seasons of the year, is an excellent precaution against un- 
 avoidable exposure. 
 
 17 What causes the difference between the hard hand 
 of a blacksmith and the soft hand of a woman ? 
 
 (See Physiology, p. 50.) 
 
 The varying thickness of the cuticle. 
 
154 ANSWERS TO PRACTICAL QUESTIONS 
 
 18. Wliy should a painter avoid getting paint on the 
 
 palm of his hand ? 
 
 (See Physiology, p. 62.) 
 
 19. Why should we not use the soap or the soiled towel 
 at a hotel ? 
 
 Because of the danger of contracting disease through the 
 
 absorbents of the skin. (See Physiology, p. 62.) There is a 
 
 similar danger in using a hair-brush or a comb at a barber 
 shop. 
 
 20. Wliich teeth cut like a pair of scissors ? 
 
 The "back teeth," as we commonly call them, when moved 
 laterally, cut somewhat in this way. In chewing the food, all 
 the "front teeth" act like scissors, as may be readily seen by 
 noticing their movements. 
 
 21. Which teeth cut like a chisel? 
 
 The incisors, or four front teeth of each jaw, have knife 
 edges ; the canine teeth have wedge-shaped edges ; the bicus- 
 pids and molars have broader crowns. "We can work the jaws 
 so as to make the front teeth either pierce like wedges or cut 
 like scissors. 
 
 22. Which should be clothed the warmer, a merchant 
 or a farmer ? 
 
 The merchant is liable to more sudden and violent changes 
 of temperature, and his body is less likely to be hardened by 
 exposure and habit to resist them. 
 
 23. Why should we not crack nuts with our teeth ? 
 
 The brittle enamel is very liable to crack, and once broken 
 can never be restored. 
 
 24. Do t he edges of the upper and lower teeth meet ? 
 
 (See Question 21.) 
 
 25. Wlien fatigued, should you take a cold bath ? 
 
 Certainly not. The system is not vigorous enough to pro- 
 duce a reaction, and the effect might be dangerous. 
 
IN HYGIENIC PHYSIOLOGY. 155 
 
 26. Why is the outer surface of a kid glove finer than 
 the inner ? 
 
 This illustrates the difference in texture between the cutis 
 and cuticle ; the dermis and epidermis. 
 
 27 WJiy will a brunette endure the sun's rays better 
 
 than a blonde ? 
 
 (See Physiology, p 51.) 
 
 The skin is perhaps of a coarser texture, and not so sensi- 
 tive to heat. May it not be also that the black pigment ab- 
 sorbs the heat and radiates it again rather than transmits it 
 directly to the internal organs ? It has also been suggested that 
 there is an increased flow of blood in the darker skin, and 
 hence increased perspiration. 
 
 28. Does patent-leather form a healthful covering for 
 the feet? 
 
 No. The pores of the leather are partly filled, and hence 
 the insensible perspiration is largely restrained. 
 
 29. IVIiy are men more frequently bald than women ? 
 
 This is to some extent the effect of the close, unventilated 
 head-covering commonly worn by men. 
 
 30. On what part of the head does baldness commonly 
 occur ? 
 
 On that part most fully covered by the hat or cap. 
 
 31. WJiat does the combination in our teeth of canines 
 and grinders suggest as to the character of our food ? 
 
 That we are to eat a mixed diet of vegetable and animal 
 food.* 
 
 * The question of the use of animal or vegetable food may well be re- 
 mitted to the arbitrament of nature, as expressed in the desires ; by which 
 it would be victoriously decided, in all such climates as ours, in favor of 
 the flesh-eater. But the sufficiency of vegetable food, if widely varied, to 
 maintain health and even strength, is not to be questioned, for those who 
 like it. When we hear that the ancient Persians lived a good deal on 
 water-cress, we naturally connect in our minds their physical inferiority 
 
156 ANSWERS TO PRACTICAL QUESTIONS 
 
 32. la a staid, formal promenade suitable exercise? 
 
 No. There is an intimate relation between the brain and 
 the muscles. The mind should be pleasantly employed to ob- 
 tain the full effect of any exercise.* The sports of children are 
 often the very perfection of healthful gymnastic exercises. 
 
 33. Is there any danger in changing the warm clothing 
 of our daily wear for the thin one of a party ? 
 
 Very great. The body is not so well protected as usual 
 against a sudden change of temperature, as in going from a 
 heated room to the carriage, and a cold is often the conse- 
 quence. This may lay the foundation of fatal disease. 
 
 34. Should we retain our overcoat, shawl, or furs, when 
 we come into a warm room ? 
 
 No. The body will become over-heated, the pores be opened, 
 and the skin be rendered susceptible to the change of tempera- 
 ture when we return into the open air. 
 
 with, the poverty of their diet ; but finding, on the other hand, that the 
 Romans, in the best period of the Republic, largely sustained themselves 
 on turnips, and that degeneracy came in as turnips went out, we are com- 
 pelled to reconsider our opinion. In brief, an exclusively vegetable food 
 may be best suited to those by whom it really is preferred. Children in 
 this respect exhibit the greatest difference ; some, with manifest advan- 
 tage, eat meat in large quantity others can hardly be prevailed on to taste 
 it, and yet retain perfect vigor. Similar differences, in all probability, exist 
 among adults; but a vegetarianism self-imposed against the promptings 
 of desire, would tend, as a vigorous writer says, to make us " not the chil- 
 dren, but the abortions of Paradise." HINTON. 
 
 * The mental operations, like all others, are connected with changes in 
 the material of the body. In all our consciousness the chemical tenden- 
 cies of the substance of the brain come into play, and thus a chain of 
 action is set up which extends throughout the system. The influence of 
 these brain-changes is felt wherever a nerve travels, and modifies, invigor- 
 ates, or depraves the action of every part. Experience gives ample proof 
 of this fact to every one, as in the sudden loss of appetite a piece of bad 
 news will cause, or in the watering of the mouth excited by the thought 
 of food. And the history of disease abounds in evidence of a similar kind : 
 hair becoming gray in a single night from sorrow, milk poisoning an infant 
 from an attack of passion in the nurse, permanent discoloration of the 
 skin from terror, are among the instances on record. HINTON. 
 
7A HYGIENIC PHYSIOLOGY. 157 
 
 35. Which should bathe the oftener, students or out- 
 door laborers? 
 
 This depends entirely on circumstances the amount of ex- 
 ercise, the individual freedom and character of perspiration, the 
 state of the system, etc. Each case must be decided by itself. 
 
 36. Is abundant perspiration injurious ? 
 
 No. It removes impure matter from the system, and hence 
 may be beneficial. It may, however, weaken the body, and 
 frequent hot baths should therefore be taken only on suitable 
 medical advice. 
 
 37. How often should the ablution of the entire body be 
 performed ? 
 
 For the preservation of perfect health there should be daily 
 morning ablution in cold or cool water, using soap sparingly. 
 A warm or tepid bath, with a free application of soap, may 
 advantageously be taken once a week, followed by a dash of 
 cool water. It is well for children and delicate persons to 
 stand in warm water, having the cold water in an extra tub or 
 basin. They can then, with a large sponge, dash the cold 
 water freely over their bodies, and get the full tonic effect of 
 the cold bath without the coldness or discomfort which might 
 otherwise ensue. A cold bath should always be quickly per- 
 formed, accompanied by vigorous rubbing to insure the reac- 
 tion. Children especially should be thoroughly rubbed and com- 
 pletely dried. Above all, let the daily wash be a delight, and 
 not a dread, to the little ones. A reluctant bath, with a hasty 
 dismissal, leaving the skin wet, the blood chilled, and the spirits 
 depressed, not only inflicts upon the helpless and unhappy 
 child a needless misery, but will be likely to result in chapped 
 skin and chronic catarrh, if in nothing worse. 
 
 38. Why is cold tvater better than warm for our daily 
 ablution ? 
 
 (See Physiology, p. 64.) 
 
 The daily repetition of the cold bath renders the system 
 less sensitive to changes in atmospheric temperature, the re- 
 verse being the case with the warm bath. Still, it should be 
 said that not every one is able to endure the cold bath. If the 
 
158 AXSWESS TO PRACTICAL QUESTIONS 
 
 skin remains cold and blue in spite of friction, it shows that 
 the reaction has not taken place, in which case the bath is an 
 injury. Or, if for some time after the bath the bather feels 
 languid and weary, it indicates that the reaction is too much 
 for his nervous system. But, in most cases, if the habit is 
 formed by beginning first with tepid water, decreasing the tem- 
 perature gradually, morning by morning, until the bather in- 
 ures himself to the coldest water, the shock and the reaction 
 will be a luxury he will not willingly abandon. In this con- 
 nection it may be said that, as water is a better conductor of 
 heat than air, water at a temperature of 75 or 80 will seem 
 cold to most persons (the normal temperature of the body being 
 about 98 Fahr.), though an atmosphere of that degree would 
 seem warm. The temperature of the room should always be 
 higher than that of the water. 
 
 39. llJiy should our clothing always fit loosely ? 
 
 (See Physiology, pp. 14, 67, 96.) 
 
 Any thing that impedes circulation is injurious. Loose un- 
 der-clothing is warmer in winter than tight under-clothing, on 
 account of the stratum of air between the body and the gar- 
 ment. (See Question 12.) The effects of tight-lacing are well 
 known.* Too close-fitting sleeves interfere with the venous cir- 
 culation of the arm, and tend to make the fingers cold and 
 blue ; while the pressure upon the nerves, which lie not far 
 
 * The evil effects of tight-lacing are not all nor always in the future. 
 Signs of distress are often quickly apparent ; the nose purples, the upper 
 bowels emit croaking sounds, while the lower become unnaturally protu- 
 berant ; the womb falls, and the breathing and the circulation of blood 
 are so hindered as often to bring on palpitations of the heart and faint- 
 ing ; especially after a full meal or in a close and sultry atmosphere. The 
 long-continued and tight pressure of corsets also wastes and impairs the 
 natural strength of the muscles of the back; so that without the usual 
 lacing there is a most uncomfortable feeling of weakness. The circulation 
 of the blood in the lower part of the lungs, from the severe compression 
 imposed upon them, becomes in an almost stagnant condition, producing 
 languor and a painful sense of lassitude. Continue this constraint, and 
 the cell-life of the lungs, liver, and stomach becomes permanently im- 
 paired, laying a sure foundation for disease in these parts whenever the 
 constitutional strength and vigor begin to fail. The Ten Laws of Health, J. 
 B. BLACK. 
 
IN HYGIENIC PHYSIOLOGY. 159 
 
 below the skin, induce neuralgia and numbness in the fingers. 
 A rigid constriction about the arm-pit will frequently result in 
 a swollen hand. Tight elastics should never be worn upon the 
 lower limbs. Aside from all the discomforts and maladies at- 
 tendant upon the wearing of tight garments, the natural ease 
 and grace of bodily movement are always more or less ob- 
 structed. 
 
 4O. Why should we take special pains to avoid clothing 
 that is colored by poisonous dye-stuffs ? 
 
 (See Physiology, p. 62.) 
 
 Because the particles of the poisonous coloring are liable to 
 be absorbed by the skin, and thus taken into the system. The 
 dangerous agent is usually arsenic, which is employed in dyeing 
 bright reds, magentas, aniline reds, and certain greens. Par- 
 ticular care should be taken in the selection of hose. Unfortu- 
 nately, the pure white stocking has gone out of style, though 
 hygienically it is greatly preferable to the highly (often poison- 
 ously) dyed one that has succeeded to fashionable favor. 
 
 4:1. WJiat general principles should guide us as to the 
 length and frequency of baths in salt or fresh water ? 
 
 (See Physiology, pp. 66, 291.) 
 
 Sea or river baths should never be prolonged to the extent 
 of sensible fatigue, and consequent inability of reaction. A 
 daily swim taken before breakfast, and limited to twenty min- 
 utes at the outside, is to most people the best of tonics. Per- 
 sons with pale skins (technically termed anaemic, or bloodless), 
 or those who are suffering from heart disease, should not at- 
 tempt sea or river bathing, or, indeed, any cold bath, except 
 under medical advice. 
 
 42. What is the beneficial effect of exercise upon the 
 functions of the skin ? 
 
 (See Physiology, p. 62; also note, p. 42.) 
 
 Increased muscular action calls for an extra supply of blood. 
 The heart responds by more rapid beating, the lungs take in 
 more oxygen, and the bodily heat is heightened. To dispose of 
 this superfluous warmth, the oil and perspiratory glands are 
 stimulated to greater activity, the impurities which naturally 
 
160 ANSWERS TO PRACTICAL QUESTIONS 
 
 escape from the body by this avenue are hastened in their exit, 
 and the skin itself becomes soft and moist. 
 
 43. How can ive best show our admiration and respect 
 for the human body ? 
 
 By conscientiously observing all the laws of physical hy- 
 giene, as well as moral purity. 
 
 44. IVTiy is the scar of a severe wound upon a negro 
 sometimes white ? 
 
 Because the cells containing the pigment or coloring matter 
 were destroyed by the severity of the wound, and have not 
 been restored. 
 
 99 ! What is the philosophy of the "change of 
 voice " in a boy ? 
 
 Up to the age of fourteen or fifteen, there is little or no 
 difference in point of size between the larynx of a boy and 
 that of a girl ; but subsequently the former grows proportion- 
 ately larger, so that at last, in the adult male, the vibrating 
 parts or vocal cords are necessarily longer than in the female. 
 They are also undoubtedly thicker, perhaps even coarser in 
 structure. From all these circumstances the adult male voice 
 is stronger, louder, and of lower pitch than the weaker and 
 higher vocal range accomplished by the female larynx. 
 
 The cause of the difference in quality of the voice, known 
 as its timbre, is not well known ; but it must undoubtedly be 
 dependent on physical, that is to say, structural peculiarities in 
 some part of the laryngeal apparatus. 
 
 The production of the different notes within the compass of 
 any one individual depends upon alterations in the length and 
 state of tension of the vocal cords, and on their degree of prox- 
 imity or separation from one another. The higher notes require 
 the vocal cords to be comparatively shorter, tighter, and more 
 closely approximated together ; while the lower notes demand 
 opposite conditions. A high note, furthermore, implies greater 
 rapidity in the movement of the air through the glottis ; but 
 the quantity of air passing is larger during the production of a 
 low note. 
 
IN HYGIENIC PHYSIOLOGY. 161 
 
 The volume or loudn&ss of the voice depends mainly on the 
 combination of quantity of air with greater force of expulsion. 
 Loudness, with clearness, also demands a peculiar resonance 
 up in the nasal cavities and sinuses. Lastly, the unnatural or 
 falsetto voice seems also to be produced by some tensive change 
 effected in the upper part of the pharynx at the back of the 
 nose : hence it is called by singers the head voice, in contradis- 
 tinction to the ordinary, or chest voice. MARSHALL. 
 
 2. Why can ive see our breath on a frosty morning ? 
 
 The vapor of the breath is condensed by the cold air. 
 
 3. When a laiv of health and a laiv of fashion conflict , 
 which should ^ve obey ? 
 
 It depends, of course, whether we prefer to be fashionable 
 or to be healthy, to obey man or God. With too many people 
 the former is of far greater importance, and in selecting an 
 article of dress, few ask or think about the latter. The conse- 
 quence is seen in the weakened frame, the prevalence of dis- 
 ease, and the shortened life. God's laws written in our bodies 
 can not be violated with impunity. 
 
 4. If we use a " bunk " bed 9 sJioidd we pack away the 
 clothes when ive first rise in the morning ? 
 
 No. They should first be thoroughly aired. 
 
 5. Why should a clothes-press be ivcll ventilated? 
 
 The clothes naturally contain the products of the insensible 
 perspiration, which passing off, pollute the air of the closet. 
 
 6. Sliould the weight of our clothing Jiang from the 
 tvalst or the shoulder ? 
 
 From the shoulder, so as to avoid the constriction of the 
 compressible organs in the abdomen. 
 
 7. Describe the effects of living in an overheated 
 room. 
 
 (1) The body becomes moro sensitive to change, and the 
 susceptibility to colds is greatly increased ; (2) the dry, heated 
 air abstracts the moisture from the skin, rendering it dry, hard, 
 and incapable of performing its normal functions. 
 
162 ANSWERS TO PRACTICAL QUESTIONS 
 
 8. Wliat habits impair the power of the lungs? 
 
 Above all others, those of a leaning posture, tight-lacing, 
 and ill-ventilation. 
 
 9. For fall 9 easy breathing in singing, should ive use 
 the diaphragm and lower ribs or the upper ribs alone ? 
 
 Nearly all the inspirations are effected by the movements 
 of the diaphragm and the inferior ribs only. From time to 
 time a deeper and more complete inspiration causes the thorax 
 to rise, not simultaneously, but successively at the base, then 
 at the apex. In the first case the respiration is diaphragmatic; 
 when the lower and middle ribs are raised, it is termed lateral; 
 and, lastly, when the first rib and clavicle take part in the 
 movement, it is costo-superior or clavicular. In diaphragmatic 
 respiration, as M. Mandl has observed, the larynx is immov- 
 able, the inspiration is easy, without effort, and permits exer- 
 tion in singing or in gymnastics for a long time and without 
 fatigue. On the contrary, persons who respire principally by 
 the upper ribs are easily fatigued, and very soon out of breath. 
 This is seen in women when the corset compresses the base of 
 the chest, and in singers who adopt, on erroneous principles, 
 the bad habit of clavicular respiration. In this last method of 
 inspiration the larynx is drawn down by the contraction of the 
 external muscles, and its action becomes painful. The effort of 
 the inspiratory muscles rapidly induces fatigue, and the inspi- 
 ration, always incomplete, becomes also more frequent. Dia- 
 phragmatic respiration is practiced by mountaineers, gymnasts, 
 and skillful singers a habit induced either by instinct, or a 
 well-directed education. Wonders of the Human Body. 
 
 10. Why is it better to breathe through the nose than 
 the mouth ? 
 
 The air passing through the nostrils becomes filtered of its 
 coarse impurities, and the chill is taken off before it strikes 
 against the tender, mucous surfaces of the larynx. 
 
 11. Why should not a speaker talk while returning 
 home on a cold night after a lecture ? 
 
 The cold air will strike against the vocal apparatus when 
 inflamed and peculiarly sensitive. 
 
IN HYGIENIC PHYSIOLOGY. 163 
 
 12. What part of the body needs the loosest clothing ? 
 
 The abdomen ; because of the delicate organs within, un- 
 protected by a bony covering. 
 
 13. What part needs the warmest ? 
 
 The feet, because they are furthest from the center of heat 
 and motion, and most exposed to cold and wet : and the neck 
 and shoulders, since here are located the delicate organs of 
 voice and respiration. 
 
 14. Why is a 6i spare bed 99 generally iinhealthful ? 
 
 Because it is apt to be damp and unventilated. 
 
 15. Is tit ere any good in sighing ? 
 
 (See Physiology, p. 82.) 
 It probably brings up the "arrears" of respiration. 
 
 10. Should a hat be thoroughly ventilated? Hotv? 
 
 1. Certainly, as the heated, foul air is injurious. 2. Several 
 openings should be made on the sides near the band. A 
 single hole at the top is quite insufficient for ventilation. 
 
 1 7. Why do the lungs of people who live in cities become 
 of a gray color ? 
 
 Probably because of the deposition of carbonaceous particles 
 which penetrate the substance of the tissues. The coloring is 
 permanent, like tattooing, where India-ink is pricked beneath 
 the skin. 
 
 18. Hoiv would tfbu convince a person that a bedroom 
 should be aired ? 
 
 Take him from the fresh, pure, invigorating out-door at- 
 mosphere into the close, depressing air of the bedroom, when 
 first vacated in the morning, and his sense of smell will satisfy 
 him of the need of ventilation. 
 
 19. IVTiat persons are tnost liable to catarrh 9 consump- 
 
 w, etc. ? 
 
 (See Physiology, p. 85.) 
 
 The victims of lung-starvation. 
 
164 ANSWERS TO PRACTICAL QUESTIONS 
 
 20. If a person is plunged under water, will any enter 
 his lungs ? 
 
 No. The epiglottis will close involuntarily, and prevent the 
 admission of water. 
 
 21. Are bed- curtains healthful ? 
 
 No. They prevent the free circulation of the air, and con- 
 fine the waste products thrown off from the body. 
 
 22. Why do some persons take " short breaths " after a 
 meal? 
 
 The distention of the stomach prevents the free action of 
 the lungs. If such persons arc not given to gluttony, the lungs 
 are small or the other organs misplaced. 
 
 23. What is the special value of public parks ? 
 
 They bring fresh air, nunshine, green grass and trees 
 within the reach of all. They are truly the "breathing-holes 
 of a city." They arc thus of incalculable benefit both on ac- 
 count of their sanitary and moral influence. 
 
 24:. Can a person become used fo bad air,, so that it ivill 
 not injure Jiini ? 
 
 The system may come to endure without complaint, but, 
 sooner or later, it never fails to inflict full punishment for the 
 infraction of nature's laws. 
 
 25. Why do ive gape when tec arc sleepy ? 
 
 (See Question 15.) 
 
 The stretching of the nerves may perhaps serve to restore 
 the equilibrium of the nervous influence, disturbed by the at- 
 tention being fixed during the day upon some absorbing occu- 
 pation. 
 
 26. Is a fashionable waist a model of art in sculpture 
 or painting ? 
 
 The Venus of Milo, in the Louvre at Paris, is the beau- 
 ideal of symmetry and beauty, yet the form indicates not a 
 "wasp-waist," but the full, free, flowing outlines of nature. 
 The sculptor and painter in copying the human figure can 
 make no improvement on its Divine Maker. 
 
IN HYGIENIC PHYSIOLOGY. 165 
 
 27. Should afire-place be closed? 
 
 (See Physiology, p. 99.) 
 No. It is a most efficient means of ventilation. 
 
 28. Why does embarrassment or fright cause a stam- 
 merer to stutter still more painfully ? 
 
 Stuttering is mainly a nervous disorder, and hence any ex- 
 citement tends to increase the impediment of the speech. 
 
 29. In the organs of voice, what parts have somewhat 
 the same office as the case of a violin and the sounding- 
 board of a piano ? 
 
 (See Popular Physics, p. 186.) 
 
 The pharynx, the mouth, and the nasal passages all act by 
 resonance to modify the voice. 
 
 30. Why should tve be careful not to " take the breath 9 ' 
 of a sick person ? 
 
 Because, in this manner, special disease germs may be di- 
 rectly transferred from the lungs of the sick person into our 
 own. It is well never to "take the breath" of any person, 
 sick or well, since impurities are constantly passing off from 
 every human system through the avenue of the lungs. 
 
 31. What special care should be taken with regard to 
 keeping a cellar clean ? 
 
 The walls and floor should be free from moisture, and any ac- 
 cumulation whatever of dust or refuse. There should be not only 
 some means of constant ventilation, but the windows ought fre- 
 quently to be opened to full currents of air from without. 
 Vegetables should never be allowed to decay in the cellar. In these 
 days of furnaces, when, in addition to the ordinary upward 
 travel of cellar odors, the sides of the registers in the rooms 
 above afford a direct means of ascent for all the foul or stag- 
 nant air that may lurk below, the basement should be the 
 sweetest and most immaculate portion of the house. 
 
 32. How is the air strained as it passes into the lungs ? 
 
 The constant motion of the cilia, which line the air-pas- 
 sages, produces an outward current, which arrests and expels 
 
166 ANSWERS TO PRACTICAL QUESTIONS 
 
 intrusive particles that, swept inward by the breath, would 
 otherwise pass into the lungs. 
 
 33. Can one really if draw the air into his lungs " ? 
 
 (See Physiology, p. 80.) 
 
 Strictly speaking, no. In the act of inspiration we so con- 
 tract the muscles as to enlarge the cavity of the chest, thus re- 
 ducing the pressure upon the lungs, upon which the external 
 atmosphere, in seeking an equilibrium, rushes in to fill the 
 space. 
 
 34. How often do we breathe ? 
 
 Ordinarily about eighteen times a minute. 
 
 35. Describe some approved method of ventilation. 
 
 (See Physiology, p. 92.) 
 
 36. What is at once the floor of the chest and the roof 
 of the abdom,en ? 
 
 The diaphragm. 
 
 37. What would you do in case of apparent death by 
 drowning or by coal-gas ? 
 
 (See Physiology, p. 264.) 
 
 38. What would you do in case of croup, 'while the 
 doctor was coming ? 
 
 (See Physiology, p. 260.) 
 
 39. How would you treat a severe burn ? 
 
 (See Physiology, p. 257.) 
 
 40. Describe the various ways in which the water in a 
 well is liable to become unwholesome. 
 
 In towns and cities organic matter, solid or in solution, 
 permeates the soil to the depth of several feet, and shallow 
 wells are therefore quite certain to be polluted, as any earth 
 used constantly as a filter will, in the course of years, lose its 
 purifying properties. Wells, too, are often placed in dangerous 
 proximity to cemeteries, cess-pools, barn-yards, vaults, etc., and 
 in many cases receive direct drainage from these pestilential 
 sources. Impurities will collect in wells that are not periodic- 
 
IN HYGIENIC PHYSIOLOGY. 167 
 
 ally cleaned, especially if the water in them is not freely ex- 
 posed to the oxygen of the air. If one must depend upon well- 
 water, the safest reliance is upon a deep-driven well. 
 
 1 47 ! Why does a dry, cold atmosp7iere favorably 
 affect catarrh ? 
 
 It tends to diminish inflammation in the mucous membrane 
 lining the nose and nasal passages. 
 
 2. Why should we put on extra covering when we lie 
 down to sleep ? 
 
 The respiration and the circulation are then less active. 
 The fire in our corporeal stoves being low, we need extra cov- 
 ering to preserve the warmth of the body. 
 
 3. Is it well to throiv off our coats or shawls when we 
 come in heated from a long walk? 
 
 No. "We need, instead, to put on extra clothing at such times 
 to keep the body from cooling too rapidly. The best hygienic 
 teachers commend the throwing of a shawl about the shoulders 
 whenever we sit down to rest after fatiguing labor. 
 
 4. JFliy are close-fitting collars or neck-ties injurious ? 
 
 They impede both respiration and circulation. 
 
 5. Which side of the heart is the more liable to inflam- 
 mation ? 
 
 The left ; because that contains the red blood just oxygenated 
 in the lungs. 
 
 6. What gives the toper his red nose ? 
 
 (See Physiology, p. 126.) 
 
 The congested state of the capillaries. 
 
 7. Why does not the arm die when the surgeon ties the 
 principal artery leading to it ? 
 
 The anastomoses of the arteries enable a collateral circula- 
 tion to be established, whereby blood is supplied to the arm. 
 
 8. Wlien a fowl is angry, ivhy does its comb redden^ 
 
168 ANSWERS TO PRACTICAL QUESTIONS 
 
 Because an extra quantity of blood is thrown into that part 
 of the body. 
 
 9. Why does a fat man endure cold better than a lean 
 one? 
 
 Fat is a good non-conductor of heat, and helps to preserve 
 the uniform temperature of the body. 
 
 1 0. IVJiy does one become thin during a long sickness ? 
 
 By absorption, the fat of the body is taken up and used to 
 supply the wants of the system. The old flesh being renewed 
 with new, vigorous material, a person often has better health 
 after such a wasting sickness than previous to it. 
 
 11. If 'hat would you do if you should come home " ivet 
 to the skin " ? 
 
 One should (1) go into a warm . room ; (2) remove all wet 
 garments ; (3) if chilled, take a hot, full or foot bath, and by 
 gentle friction restore the circulation ; (4) put on dry clothing. 
 
 12. Wit en the cold air strikes the face, why does it first 
 blanch and then flush ? 
 
 The muscles and blood-vessels of the surface are contracted 
 by the cold, and the blood is driven back toward the heart. 
 The reaction which ensues forces the blood again toward the 
 skin, and this flushes with the incoming tide. The face is 
 therefore first whitened and then reddened. 
 
 13. What must be the effect of tight lacing upon the 
 circulation of the blood ? 
 
 It must, by contracting the blood-vessels, impede the flow 
 of the blood, and by decreasing the quantity furnished the 
 various organs, injure their action. Thus, finally, it will im- 
 pair the quality of the blood. 
 
 14. Do you knoiv the position of the large arteries in 
 the limbs, so that in case of accident you could stop the 
 floiv of blood ? 
 
 These can be located by examining the cut in Physiology, 
 page 104, or any good chart of the circulation. 
 
/JV HYGIENIC PHYSIOLOGY. 169 
 
 15. When a person is said to be " good-hearted," is it 
 a physical truth ? 
 
 The expressions, large-hearted, good-hearted, etc., are re^ 
 mains of the old idea that the affections are located in the 
 heart rather than in the brain the seat of the mind and all its 
 attributes.* 
 
 16. Why does a hot foot-bath often relieve the head- 
 ache ? 
 
 (Sec Physiology, p. 126.) 
 
 It withdraws blood from the head, and so relieves the con- 
 gested state of that organ. 
 
 f 
 
 17 ' IVTiy does the body of a drowned or strangled per- 
 son turn blue ? 
 
 * In connection with this subject, the following from a recent article 
 by Dr. Wm. A. Hammond, will be found of interest: "In the very earliest 
 times of which we have any record, and even at the present day among 
 barbarous nations, the idea existed that the brain was not the only organ 
 concerned in the production of mind. . . . Doubtless, its origin was due to 
 the fact that, under the influence of certain emotions, there are disturb- 
 ances in the organs with which they are associated. Thus, love quickens 
 the action of the hearb ; mental depression or anger deranges the liver ; 
 and pity produces what is sometimes" called ' a sinking feeling ' at the pit 
 of the stomach. It has been customary with modern writers to regard 
 these disturbances as being the effects of emotions that originated in the 
 brain, and not as indicating that the organs in which they are felt have 
 any thing to do with the evolution of love, or anger, or fear, or compassion, 
 or any other passion or feeling. . . . The idea has become so widely spread 
 among educated persons that the brain is the only organ of the body that 
 has any direct relation as a generator with the mind, that it seems like a 
 tremendous blow at the system of existing facts to attempt to take from it 
 any of its power. But it is only recently that physiologists and patholo- 
 gists are beginning to make a thorough investigation into that great divis- 
 ion of the nervous system consisting of the sympathetic nerves and their 
 
 ganglia Now,' it is not unreasonable to suppose that these 
 
 masses of the tissue in question, that are placed around the heart, the 
 liver, the spine, and other organs, and in vast number in their substance, 
 have some influence in causing the production of those emotions that 
 make themselves felt in the parts of the body with which former univer- 
 sal beliefs, and our present forms of speech, have associated them. We 
 find, too, as an additional fact in support of this view, that in certain 
 mental affections, characterized by great emotional disturbances, these 
 ganglia are in various parts of the body the seats of disease." 
 
170 ANSWERS TO PRACTICAL QUESTIONS 
 
 The blood is not purified in the lungs, and so blue or ve- 
 nous blood fills the vessels. 
 
 18. What are the little "kernels" in the arm-pits ? 
 
 (See Physiology, p. 125.) 
 
 They are the lymphatic glands, which sometimes become 
 swollen. 
 
 19. When we are excessively ivarm, would the ther- 
 mometer show any rise of temperature in the body ? 
 
 (See Physiology, p. 120, note.) 
 
 Probably not. In health, the average temperature of the 
 body does not vary mere than two degrees. 
 
 20. What forces besides that of the heart aid in pro- 
 pelling the blood ? 
 
 (See FLINT'S Physiology The Circulation ; CUTLER'S Analytic Anatomy, etc . 
 p. 166, etseq.) 
 
 The elasticity of the arteries and the veins, the force of 
 capillary attraction in the capillaries, etc. 
 
 21. iriiy can the pulse be best felt in the ivrist ? 
 
 It is, in general, a mere matter of convenience. We can 
 feel it not only in the radial artery at the wrist, but in the 
 carotid of the neck, the temporal of the forehead, the popliteal* 
 in the inner side of the knee, etc. 
 
 22. Wliy are starving people exceedingly sensitive to 
 any jar ? 
 
 The marrow of the bones is absorbed, and hence the shock 
 of a jar is unbroken. The nervous system is also weakened by 
 the general prostration. 
 
 23. Why will friction, an application of horse-radish 
 leaves , or a blister relieve internal congestion ? 
 
 They bring the blood to the surface of the body, and so re- 
 lieve the internal organ. 
 
 * If the hollow of the knee of one leg be allowed to rest upon the knee 
 of the other one, it may be remarked that the point of the suspended foot 
 moves visibly up and down at each beat of the pulse. 
 
IN HYGIENIC PHYSIOLOGY. 171 
 
 24. Why are students very liable to cold feet ? 
 
 Because the tendency of the blood is toward the head, to 
 supply the waste in that part of the body. 
 
 25. Is the proverb that " blood is thicker than water 7f 
 literally true ? 
 
 (See DBAPEB'S Human Physiology, p. 112.) 
 
 The specific gravity of the blood varies from 1.050 to 1.059. 
 
 26. What is the effect upon the circulation of 6( holding 
 the breath"? 
 
 The blood is not oxygenated, the products of waste accumu- 
 late in the system, the circulation is impeded, the blood-vessels 
 become distended, and are liable to burst, while all the delicate 
 organs, especially the brain, are oppressed by congestion. 
 
 27. Which side of the heart is the stronger ? 
 
 The left, which drives the blood to the extremities. 
 
 28. Hoiv is the heart itself nourished? 
 
 The coronary arteries springing from the aorta just after 
 its origin, carry blood to the muscular walls of the heart: the 
 venous blood comes back through the coronary veins, and 
 empties directly into the right auricle. 
 
 29. Does any venous blood reach the heart without 
 coming through the venm cavce ? 
 
 (See Question 28.) 
 
 30. What would you do, in the absence of a surgeon, in 
 the case of a severe wound ? 
 
 (See Physiology, pp. 128, 258.) 
 
 31. What would you do in case of a fever ? 
 
 (See Physiology, p. 263.) 
 
 32. What is the most injurious effect of alcohol upon 
 
 the blood ? 
 
 (See Physiology, p. 144.) 
 
 Its action upon the red corpuscles. 
 
 33. Are our bodies the same from day to day ? 
 
 No, they are constantly changing. 
 
172 ANSWERS TO PRACTICAL QUESTIONS 
 
 34. Shoiv hoiv life conies by death. 
 
 (See Physiology, p. 122.) 
 
 35. Is not the truth just stated as aj^plicable to moral 
 and intellectual as to physical life ? 
 
 Yes. We increase our moral and intellectual strength in 
 proportion as we use those powers. 
 
 36. What vein begins and ends ivlth capillaries ? 
 
 (See Physiology, p. 161.) 
 
 The portal vein, which begins with capillaries in the digestive 
 organs, and ends with the same kind of vessels in the liver. 
 
 37. Hy what process is alcohol always formed? Does 
 it exist in nature ? 
 
 By the process of fermentation. It has been generally be- 
 lieved not to exist in nature, but recent experiments have seemed 
 to indicate that it does so exist, though in extremely minute 
 quantities. "Professor Muntz, of the National Agronomic In- 
 stitute, in Paris, has, by refined chemical tests, discovered evi- 
 dences of alcohol in cultivated soils, in rain water, in sea and 
 river water, and in the atmosphere. ... It appears probable 
 that the alcohol originates in the soil, from the fermentation of 
 the organic matters in it, and is thence diffused as vapor in the 
 atmosphere." W. O. ATWATEK, Century Magazine, May, 1888. 
 
 38. What percentage of alcohol is contained in the dif- 
 ferent kinds of liquor ? 
 
 Ale and porter contain from six to eight per cent. ; wine, 
 from seven to seventeen per cent. ; brandy and whiskey, from 
 forty to fifty per cent. 
 
 39. Does cider possess the same intoxicating principle 
 as brandy? 
 
 Yes, because cider that has begun to ferment contains alco- 
 hol, which is the intoxicating principle in all spirituous drinks. 
 
 40. Describe the general properties of alcohol. 
 
 It is volatile; antiseptic, a solvent. It burns without smoke, 
 and with great heat, and has a remarkable affinity for water. 
 It boils at 172 Fahr. 
 
IN HYGIENIC PHYSIOLOGY. 173 
 
 41. Shoiv that alcohol is a narcotic poison. 
 
 (See answer to Question 42.) 
 
 42. If alcohol is not a stimulant, how does it cause the 
 heart to overwork ? 
 
 Recently, physiological research has served to explain the 
 reason why, under alcohol, the heart at first beats so quickly, 
 why the pulses rise, and why the minute blood-vessels become 
 so strongly injected. 
 
 At one time it was imagined that alcohol acts immediately 
 upon the heart, by stimulating it to increased motion ; and 
 from this idea false idea, I should say of the primary action 
 of alcohol, many erroneous conclusions have been drawn. We 
 have now learned that there exist many chemical bodies which 
 act in the same manner as alcohol, and that their effect is not to 
 stimulate the heart, but to weaken the contractile force of the 
 extreme and minute vessels which the heart fills with blood at 
 each of its strokes. These bodies produce, in fact, a paralysis 
 of the organic nervous supply of the vessels which constitute 
 the minute vascular structures. The minute vessels when para- 
 lyzed offer inefficient resistance to the force of the heart, and the 
 pulsating organ thus liberated, like the main-spring of a clock 
 from which the resistance has been removed, quickens in action, 
 dilating the feebly-resistant vessels, and giving evidence really 
 not of increased, but of wasted power. B. W. RICHARDSON. 
 
 43. IVliy is the skin of a drunkard always red and 
 blotched ? 
 
 It is the effect of alcoholic action on the vascular structure. 
 
 44. What danger is there in occasionally using alco- 
 holic drinks ? 
 
 Aside from injurious temporary effects, there is always the 
 supreme danger of forming a habit which will become uncon- 
 trollable. 
 
 45. Wliat is meant by a fatty degeneration of the 
 
 heart ? 
 
 (See Physiology, p. 143.) 
 
 In this disease, fat is substituted for true muscular tissue. 
 
174 ANSWERS TO PRACTICAL QUESTIONS 
 
 46. What Jceeps the blood in circulation between the 
 beats of the heart ? 
 
 The blood starts with a rush from the heart by the force 
 of its action ; the expansion and contraction of the arteries, 
 into which it is thus powerfully propelled, impart a steady on- 
 ward pressure, which sends it to the capillaries ; there the proc- 
 esses of oxidation, nutrition, and secretion draw the current on- 
 ward, and push it out toward the veins ; thence it is forced back 
 to the heart by the power originated in the capillaries. (See 
 Draper's Human Physiology, large edition, p. 145.) 
 
 47. Wliat is the office of the capillaries ? 
 
 (See Physiology, p. 373, note.) 
 
 48. Does alcohol interfere with this function ? 
 
 (See Physiology, p. 117, note.) 
 
 Alcohol sometimes causes the red corpuscles to adhere in 
 masses, which obstruct their passage through the tiny capillary 
 tubes. 
 
 49. How does alcohol interfere with the regular office 
 of the membranes ? 
 
 (See Physiology, p. 143.) 
 
 It absorbs their moisture, and causes them to become dry, 
 hard, and thick. 
 
 50. IIoiv does it chech the j)rocess of oxidation ? 
 
 (See Physiology, pp. 145, 146.) 
 
 By its effect upon the red blood-corpuscles, destroying their 
 efficiency as oxygen-carriers. 
 
 ! &71. How do clothing and shelter economise food ? 
 
 The force which would be converted into heat to preserve 
 the temperature of the body, is saved. The food needed to 
 supply this amount of force may be reserved or changed into 
 flesh, or into other forms of force. 
 
 2. Is it well to taJce a long walk before breaJcfast ? 
 
 (See Physiology, p. 41.) 
 A vigorous person in good health and in a healthy region 
 
IN HYGIENIC PHYSIOLOGY. 175 
 
 may do so, but one in ill health, or in a malarious district, 
 needs to be braced with food before taking any except very light 
 exercise. 
 
 3. Why is warm food easier to digest than cold ? 
 
 Heat favors the chemical change whereby the food is pre- 
 pared for assimilation. 
 
 4. Why is salt beef less nutritious than fresh ? 
 
 (See Physiology, p. 187, note.) 
 
 The salts and juices of the meat are extracted by the brine, 
 
 3. What should be the food of a man recovering from a 
 fever ? 
 
 It should be that which is nutritious, easily digested, and 
 not over-stimulating. Beef-tea or essence * is generally com- 
 mended. As soon as the patient will bear it, beefsteak, tender, 
 broiled, and not overdone, is most beneficial. 
 
 0. Is a cup of black coffee a healthful close to a hearty 
 dinner ? 
 
 The tannic acid contained in tea and coffee is neutralized 
 by the milk generally used with these beverages. In cafe noir, 
 black or clear coffee, the tannic acid acts unfavorably on the 
 mucous membrane lining the stomach. Besides, the coffee, like 
 a dessert, is superfluous, the appetite being already satisfied. 
 It therefore tends, both actively and negatively, to delay the 
 digestion of the meal. The glass of wine sometimes taken to 
 aid digestion merely deadens the sensibility of the stomach, so 
 that the food is hurried, half-digested, out into the intestines, f 
 
 * Dr. Martindale gives the following recipe for making this essence : 
 Cat a quantity of lean beef into small pieces, put it into a strong bottle, 
 without water, cork it loosely, so that the steam can escape, and immerse 
 tho bottle to its neck in a vessel of cold water. Place on the fire, and boil 
 for two hours ; then pour off the essence. 
 
 t Mix some bread and meat with gastric juice ; place them in a vial, 
 and keep that vial in a sand-bath at the slow heat of 98 degrees, occasion- 
 ally shaking briskly the contents, to imitate the motion of the stomach ; 
 you will find, after six or eight hours, the whole contents blended into one 
 
176 ANSWERS TO PRACTICAL QUESTIONS 
 
 7. Should iced ivater be used at a meal? 
 
 Only a person in robust health can endure the shock of 
 drinking iced water at a meal. Indeed, drinking of iced water 
 under any circumstances is dangerous and hurtful. If used at 
 all, it should be carefully and slowly sipped, a little at a time. 
 
 8. Why is strong tea or coffee injurious ? 
 
 The tannic acid acts unfavorably on the coatings of the 
 stomach.* The nervous system is over-stimulated, and, when 
 the reaction occurs, becomes correspondingly depressed and 
 weakened. The constant decay of the body, so essential to its 
 highest activity, is greatly retarded. Wakefulness is often in- 
 duced, and thus the organs are deprived of that rest which is 
 absolutely necessary for perfect health. 
 
 9. Should food or drink be taken hot ? 
 
 The pepsin of the gastric juice, in order to produce its 
 effect, must have a moderately warm temperature, neither too 
 hot nor too cold. The gastric juice will not act upon the food 
 when near the freezing point of water, neither will it have any 
 effect if raised to the neighborhood of a boiling temperature. 
 It must be intermediate between the two ; and its greatest ac- 
 tivity is about 100 degrees Fahrenheit, which is exactly the 
 temperature of the interior of the living stomach. D ALTON'S 
 Physiology, p. 103. 
 
 10. Are fruit-cakes, rich pastry, and puddings ivhole- 
 
 some ? 
 
 (See BLACK'S Ten Laws of Health, p. 83, et seq.) 
 
 They are too concentrated. They are not easily penetrated 
 by the juices of the system, and hence are not quickly digested. 
 They stimulate the appetite, and so lead to gluttony. They 
 supply the system with an over-abundance of nutrition, for 
 
 pultaceous mass. If to another vial of food and gastric juice, treated in 
 the same way, you add a glass of pale ale or a quantity of alcohol, at the 
 end of seven or eight hours, or even some days, the food is scarcely acted 
 upon at all. 
 
 * Tea contains from 14 to 16 per cent, of this astringent substance, 
 and coffee not over 6 per cent. YOUMANS. 
 
IN HYGIENIC PHYSIOLOGY. 177 
 
 which the blood has no use, and so lead to biliousness and other 
 diseases of the blood and digestive organs. 
 
 11. Why are warm, biscuit and bread hard of diges- 
 tion ? 
 
 They form a pasty mass, which the juices of the digestive 
 organs penetrate very slowly. 
 
 12. Should any stimulants be used in youth ? 
 
 No. The system is then vigorous, and all its functions 
 promptly performed. If stimulants are ever used, it should be 
 when the body needs forcing, as when recovering from disease, 
 or languid with the decay of the natural powers in old age. 
 
 13. Why should bread be made spongy ? 
 
 (See Question 11.) 
 
 14. Which should remain longer in the mouth, bread 
 or meat ? 
 
 Bread, since the pepsin is essential to the conversion of 
 starch into sugar. 
 
 15. Why should cold ivater be used in making soup, 
 and hot in boiling meat ? 
 
 In the former case, we desire to extract the juices of the 
 meat; in the latter, to retain them by quickly coagulating the 
 albumen on the surface of the meat. 
 
 16. Name the injurious effects of over-eating. 
 
 (See Physiology, p. 176.) 
 
 17. Why do not buckwheat cakes, with syrup and 
 butter, taste as well in July as in January ? 
 
 In tne winter, the system craves highly carbonaceous food ; 
 in the summer, it relishes cooling, acid drinks, and an unstimu- 
 lating diet. 
 
 18. Why is a late supper injurious ? 
 
 The system is wearied with the day's labor, and the stom- 
 acn is unfitted to undertake the task of digesting a meal as 
 
178 ANSWERS TO PRACTICAL QUESTIONS 
 
 much as the body is to begin a new day's task unrefreshed by 
 sleep.* 
 
 * Being allowed for once to speak, I would take the opportunity to 
 set forth how ill, in all respects, we stomachs are used. From the begin- 
 ning to the end of life, we are either afflicted with too little or too much, 
 or not the right thing, or things which are horribly disagreeable to us ; or 
 are otherwise thrown into a state of discomfort. I do not think it proper 
 to take up a moment in bewailing the Too Little, for that is an evil which 
 is never the fault of our masters, but rather the result of their misfor- 
 tunes; and, indeed, we would sometimes feel as if it were a relief from 
 other kinds of distress if we were put upon short allowance for a few 
 days. But we conceive ourselves to have matter for serious complaint 
 against mankind in respect of the Too Much, which is always an evil vol- 
 untarily incurred. What a pity that in the progress of discovery we can 
 not establish some means of a good understanding between mankind and 
 their stomachs ; for really the effects of their non-acquaintance are most 
 vexatious. Hitman beings seem to be, to this day, completely in the dark 
 as to what they ought to take at any time, and err almost as often from 
 ignorance as from depraved appetite. Sometimes, for instance, when we 
 of the inner house are rather weakly, they will send us down an article 
 that we could deal with when only in a state of robust health. Some- 
 times, when we would require a mild vegetable diet, they will persist in 
 the most stimulating and irritating of viands. 
 
 "What sputtering we poor stomachs have when mistakes of that kind 
 occur ! What remarks we indulge in regarding our masters 1 " What's this, 
 now?" will one of us say ; "ah, detestable stuff 1 What a ridiculous fellow 
 that man is 1 Will he never learn ? Just the very thing I did not want. 
 If he would only send down a bowl of fresh leek soup or barley broth, 
 there would be some sense in it " ; and so on. If we had only been allowed 
 to give the slightest hint now and then, like faithful servants as we are, 
 from how many miseries might we have saved both our masters and our- 
 selves ! 
 
 I have been a stomach for about forty years, during all of which 
 time I have endeavored to do my duty faithfully and punctually. My mas- 
 ter, however, is so reckless, that I would defy any stomach of ordinary 
 ability and capacity to get along pleasantly with him. The fact is, like 
 almost all other men, he, in his eating and drinking, considers his own 
 pleasure only, and never once reflects on the poor wretch who has to be 
 responsible for the disposal of every thing down-stairs. Scarcely on any 
 day does he fail to exceed the strict rule of temperance ; nay, there is 
 scarcely a single meal which is altogether what it ought to be. My life is 
 therefore one of continual worry and fret ; I am never allowed to rest 
 from morning till night, and have not a moment in the four-and-twenty 
 hours that I can safely call my own. My greatest trial takes place in the 
 evening, when my master has dined. If you only saw what a mess this 
 
IN HYGIENIC PHYSIOLOGY. 179 
 
 19. What makes a man "bilious"? 
 
 (See HALL'S Health by Good Living, p. Ill, et seq.) 
 
 The liver strains the bile out of the blood. This waste mat- 
 ter is not withdrawn when the liver is inactive, and hence the 
 face and eyes become yellow the color of bile, and the func- 
 tions all become torpid. 
 
 said dinner is soup, fish, flesh, fowl, ham, rice, potatoes, table-beer, sherry, 
 tart, pudding, cheese, bread, all mixed up together. I am accustomed to 
 the thing, so don't feel much shocked ; but my master himself would faint 
 at the sight. The slave of dxity in all circumstances, I call in. my friend 
 Q-astric Juice, and we set to work with as much good-will as if we had the 
 most agreeable task in the world before us. But, unluckily, my master has 
 an impression very firmly fixed upon him that our business is apt to be 
 vastly promoted by an hour or two's drinking; so he continues at table 
 among his friends, and pours down some bottle and a half of wine, per- 
 haps of various sorts, that bothers Gastric Juice and me to a degree which 
 no one can have any idea of. In fact, this wine undoes our work almost 
 as fast as we do it, besides blinding and poisoning us poor servants into 
 the bargain. On many occasions I am obliged to give up my task for the 
 time altogether ; for while this vinous shower is going on I would defy the 
 most vigorous stomach in the world to make any advance in its business 
 worth speaking of. Sometimes things go to a much greater length than at 
 others : and my master will paralyze us in this manner for hours, not 
 always, indeed, with wine, but occasionally with punch, one ingredient of 
 which the lemon is particularly odious to us. All this time I can hear 
 him jollifying away at a great rate, drinking health to his neighbors, and 
 ruining his own. 
 
 I am a lover of early hours, as are my brethren generally. To this 
 we are very much disposed by the extremely hard work which we usually 
 undergo during the day. About ten o'clock, having, perhaps, at that time 
 got all our labors past, and feeling fatigued and exhausted, we like to sink 
 into repose, not to be again disturbed till next morning at breakfast-time. 
 Well, how it may be with others T can't tell ; but so it is, that my master 
 never scruples to rouse me up from my first sleep, and give me charge of 
 an entirely new meal, after I thought I was to be my own master for the 
 night. This is a hardship of the most grievous kind. Only imagine me, 
 after having gathered in my coal, drawn on my night-cap, and gone to 
 bed, called up and made to take charge of a quantity of stuff which I 
 know I shall not be able to get off my hands all night ! Such, O mankind, 
 are the woes which befall our tribe in consequence of your occasionally 
 yielding to the temptations of " a little supper." I see turkey and tongue 
 in grief and terror. Macaroni fills me with frantic alarm. I behold jelly 
 and trifle follow in mute despair. O that I had the power of standing be- 
 side my master, and holding his unreflecting hand, as he thus prepares for 
 
180 ANSWERS TO PRACTICAL QUESTIONS 
 
 20. WJiat is the best remedy ? 
 
 Diet to give the organs rest, and active exercise to arouse 
 the secretions and the circulation. 
 
 21. What is the practical use of hunger ? 
 
 To prompt us to furnish the body with sufficient food. 
 
 22. How can jugglers drink when standing on their 
 heads ? 
 
 Because water does not fall into the stomach by its own 
 weight, but is conveyed thither from the mouth by the con- 
 traction of the muscular bands of the oesophagus. 
 
 23. ^Vhy do tve relish btitter on bread ? 
 
 Butter supplies the carbonaceous element in which bread is 
 lacking. 
 
 my torment and his own 1 Here, too, the old mistaken notion about the 
 need of something stimulating besets him, and down comes a deluge of 
 hot spirits and water, that causes me to writhe in agony, and almost sends 
 G-astric Juice off in the sulks to bed. Nor does the infatuated man rest 
 here. If the company be agreeable, one glass follows another, while I am 
 kept standing, as it were, with my sleeves tucked up, ready to begin, but 
 unable to perform a single stroke of work. 
 
 I feel that the strength which I ought to have at my present time of 
 life has passed from me. I am getting weak, and peevish, and evil-disposed. 
 A comparatively small trouble sits long and sore upon me. Bile, from being 
 my servant, is becoming my master ; and a bad one he makes, as all good 
 servants ever do. I see nothing before me but a premature old age of 
 pains and groans, and gripes and grumblings, which will, of course, not 
 last over long; and thus I shall be cut short in my career, when I should 
 have been enjoying life's tranquil evening, without a single vexation of 
 any kind to trouble me. Were I of a revengeful temper, it might be a 
 consolation to think that my master the cause of all my woes must suffer 
 ftnd sink with me ; but I don't see how this can mend my own case ; and, 
 from old acquaintance, I am rather disposed to feel sorry for him, as one 
 who has been more ignorant and imprudent than ill-meaning. In the same 
 spirit let me hope that this true and unaffected account of my case may 
 prove a warning to other persons how they use their stomachs ; for, they 
 may depend upon it, whatever injustice they do to us, in their days of 
 health and pride, will be repaid to themselves in the long-run our friend 
 Madame ISTature being a remarkably accurate accountant, who makes no 
 allowance for ignorance or mistakes. CHAMBEKS' Memoir of a /Stomach, 
 
IN HYGIENIC PHYSIOLOGY. 181 
 
 24. What ivould you do if you had taken, arsenic by 
 
 mistake ? 
 
 (See Physiology, p. 265.) 
 
 25. Why should ham and sausage be thoroughly 
 cooked ? 
 
 The trichina, which frequents pork, is only destroyed at a 
 high temperature. 
 
 26. Why do ive wish butter on fisJi, eggs with tapioca, 
 oil on salad, and milk with rice ? 
 
 To supply the elements of food lacking in the composition 
 of fish, tapioca, etc. 
 
 27. Explain the relation of food to exercise. 
 
 Their relation is exceedingly intimate. If we eat much we 
 should take more exercise, and if, on the contrary, we labor 
 more, we desire additional food. Violent exercise, directly after 
 a hearty meal, is injurious ; but a gentle, quiet half-hour's 
 saunter will greatly benefit the digestion. 
 
 28. How do you explain the difference in the manner 
 of eating between carnivorous and herbivorous animals ? 
 
 Meat requires less saliva to aid in its digestion, and hence 
 it is mainly digested in the stomach ; while vegetable food 
 needs to be thoroughly masticated and incorporated with the 
 
 salivary mucus. 
 
 i 
 
 29. Why is a child's face plump and an old man's 
 wrinkled ? 
 
 In the child the processes of nutrition are more active than 
 those of waste. The reverse is the case in old age. 
 
 30. Shoiv how life depends on repair and waste. 
 
 (See Popular Chemistry, p. 19, et seq. ; and Physiology, p. 122.) 
 
 31. What is the difference between the decay of the 
 teeth and the constant decay of the body ? 
 
 The particles of the teeth lost by decay are not renewed, 
 while in the body they are replaced as fast as worn out. The 
 
182 ANSWERS TO PRACTICAL QUESTIONS 
 
 soundness of teeth is often affected by the general health. It 
 has been said that a man who can preserve his teeth till he is 
 fifty years old may count on keeping them through life. 
 
 32. Should biscuit and cake containing yellow sf>ots of 
 soda be eaten ? 
 
 Certainly not. The alkali neutralizes the acids of the ali- 
 mentary juices, and thus impairs their functions, while it cor- 
 rodes and irritates the delicate mucous lining of the digestive 
 organs. 
 
 33. Tell hoiv the body is composed of organs, how or- 
 gans are made up of tissues, and how tissues consist of 
 cells. 
 
 (See Physiology, p. 175, note.) 
 
 34. Why do we not need to drink three pints of water 
 
 per day ? 
 
 (See Physiology, p. 151.) 
 
 The amount of water one needs depends upon the charac- 
 ter of his food, the nature of his labor, and the activity of the 
 three eliminating organs the skin, the kidneys, and the lungs. 
 One perspiring freely, or eating dry food, needs more drink 
 than one whose skin is inactive, or whose food consists, in 
 part, of soups or watery vegetables. 
 
 35. Why, during a pestilence, are those who use liquor's 
 as a beverage the first, and often the only victims ? 
 
 The nervous system has become impaired, the digestion weak- 
 ened, and the blood impoverished ; hence, the functions of the 
 body being disturbed, its ability to resist disease is greatly less- 
 ened. 
 
 36. What two secretions seem to have the same general 
 use ? 
 
 The saliva and the pancreatic juice both change starch into 
 sugar. They have other important uses, however, .in the pro- 
 cess of digestion. The former softens the food and aids in the 
 work of mastication, while the latter emulsifies the fats. 
 
 37. How may the digestive organs be strengthened ? 
 
 The digestive organs, like the other organs, are strength- 
 
7.V HYGIENIC PHYSIOLOGY. 183 
 
 ened by judicious labor. The stomach is a muscle, and, like 
 muscle generally, grows strong by use and weak by disuse. 
 The same laws should govern one in his daily exercise of every 
 organ brain, hand, and stomach. 
 
 38. Is the old rule, " after dinner sit awhile," a good 
 one? 
 
 Yes ; a certain period of rest, after a hearty meal, assists 
 the process of digestion. 
 
 39. Wliat would you do if you had taken laudanum 
 by mistalw ? Paris green ? Sugar of lead ? Oxalic acid ? 
 Phosphorus from matches ? Ammonia ? Corrosive sub- 
 limate ? 
 
 (See Physiology, p. 266.) 
 
 40. IVJiat is the simplest way to produce vomiting, so 
 essential in case of accidental poisoning ? 
 
 If mustard is at hand, mix a little thoroughly with warm 
 water, and drink immediately ; if mustard is not convenient, 
 warm soap-suds will do ; if neither is within reach, the finger 
 thrust gently down the throat may serve the purpose till other 
 means can be procured, or medical aid arrives. 
 
 41. In what ^vay does alcohol- interfere with the diges- 
 tion ? 
 
 " Alcohol in certain quantities will harden meat, and there- 
 by interfere with its digestion ; it will further precipitate pep- 
 sin and peptones ; and in large quantities it will also stop the 
 secretion of gastric juice, increase the secretion of mucus, and 
 even lead to vomiting." 
 
 42. Is alcohol assimilated ? 
 
 (See Physiology, p. 178.) 
 No. 
 
 43. What is the effect of alcohol on the albuminous sub- 
 stances ? 
 
 Pure brandy held in the mouth a short time will cause a 
 burning sensation, and the inside of the cheek will become 
 slightly whitened and corrugated. This effect is due to the 
 
184 ANSWERS TO PRACTICAL QUESTIONS 
 
 albuminous substances in the mucous membrane being partly 
 coagulated by the alcohol, and it illustrates the action of this 
 agent upon the tissues. 
 
 44. Is there any nourishment 111 beer? 
 
 The following table will show at a glance the materials 
 required for, and the result of, brewing : 
 
 Materials. Chief Compounds in Beer. 
 
 Alcohol, or spirits of wine, from 3 to 8 per cent. 
 
 Malt. 
 Water. 
 Hops. 
 
 Yeast from a pre- 
 vious brewing. 
 
 Dextrine, about 4.5 per cent. 
 
 Albuminoids, 0.5 " 
 
 Sugar, 0.5 " 
 
 Acetic and succinic acids, 0.3 per cent. 
 
 Carbonic acid, 0.15 per cent. 
 
 Mineral matter, 0.3 " 
 
 Here it is seen that the nutriment of the malt has been 
 converted into the stimulant alcohol. Whatever nourishment 
 there may be is of a saccharine nature, the dextrine when in 
 the stomach becoming converted into sugar. Of the two neces- 
 sary nourishing elements the nitrogenous and the carbonaceous 
 the former is practically wanting ; and of the latter there is 
 not enough to justify the use of malt liquor for the sake of it. 
 The chief difference between porters or stouts, and ales, con- 
 sists in the malt from which the former is made, having been 
 more highly dried. London Medical Temperance Journal. 
 
 45. Show how the excessive use of alcohol may first in- 
 crease and after ward decrease the size of the liver. 
 
 In the case of cirrhosis (sometimes called gin - drinker's 
 liver), the liver first becomes enlarged from exudation into the 
 connective tissue. After a time, this becomes organized into 
 fibrous tissues, and these fibrous bands contract and press to- 
 gether the blood-vessels and cells of the liver, until both be- 
 come atrophied and ultimately destroyed. In this way the 
 organ becomes much smaller in size, and greatly reduced in 
 weight. 
 
 46. Will liquor help one to endure cold and exposure ? 
 
 (See Physiology, p. 183.) 
 
IN HYGIENIC PHYSIOLOGY. 185 
 
 No. Experiments with Arctic voyagers have abundantly 
 proved this, while the certainty that alcohol, in its secondary 
 effect, lowers the temperature of the body, places the fact be- 
 yond dispute. 
 
 47' What is a fatty degeneration of the kidneys ? 
 
 v (See Physiology, p. 181.) 
 
 48. Contrast the action of alcohol and water in the 
 
 body. 
 
 (See Physiology, p. 178, note.) 
 
 49. Is alcohol, in any proper sense of the term, a food ? 
 
 This is a mooted point between the defenders and the op- 
 posers of alcoholic drinks. The author of this Manual consid- 
 ers that the weight of argument and the preponderance of emi- 
 nent authorities justify a decided "No" to this question. 
 
 50. Docs liquor strengthen the muscles of a working- 
 man ? 
 
 (See Physiology, p. 183.) 
 
 On the contrary, the strength of muscle is directly im- 
 paired. Dr. Parkes, an eminent English physician, tested this 
 in a practical way. Taking a certain number of working-men 
 of similar age, equal health, and provided with the same 
 amount of food, he divided them into two gangs, agreeing to 
 pay them wages in proportion to work performed. The first 
 gang he supplied with a daily ration of drink, but withheld it 
 from the second. During the first hour or two the "alcoholic 
 gang " went decidedly ahead of the other. Then they began to 
 flag, while the " non-alcoholics " went steadily on, and before 
 the day was done had far outstripped the drinkers. He then 
 reversed the experiment, giving the second gang an alcoholic 
 ration, and withholding it from the first. The result was the 
 same the non-drinkers always coming out ahead. So decided 
 was the result of the experiment, and so deeply did it impress 
 the men who were engaged in it, though they were not aware 
 of its full significance, that the alcohol men begged to be put 
 upon the non-alcohol gang, in order, as they expressed it, that 
 they " might make a little more money." 
 
 51. Is liquor a wholesome " tonic 9 '? 
 
186 ANSWERS TO PRACTICAL QUESTIONS 
 
 Certainly not a "wholesome" tonic, nor a true "tonic" in 
 any sense, for the reasons elaborated in the answers to the pre- 
 vious questions. A real tonic builds up the system, and puts it 
 upon a permanent basis of healthy function. The effect of 
 alcohol is to impair, not to build up. 
 
 52. Is it a good plan to talce a glass of liquor before 
 dinner ? 
 
 Alcohol is peculiarly injurious when taken upon an empty 
 stomach, and furnishes a sorry preparation for the proper di- 
 gestion of food. 
 
 (See answers to Questions 42, 43.) 
 
 224^. Why is the pain of incipient hip-disease fre- 
 quently felt in the knee ? 
 
 *Phe sensation of pain is located by the mind, at the part 
 of the body where the injured nerve takes its rise. 
 
 2. IVIiy does a child require more sleep than an aged 
 person ? 
 
 The processes of nutrition are going on rapidly, and, in 
 youth, much rest is required to repair the losses of each day; 
 in age, waste predominates, and the repairs made are of a 
 temporary character. The building is soon to be torn down, 
 and little effort is taken to beautify or strengthen that which 
 is to be used for so short a time. 
 
 3. When you put your finger in the palm of a sleeping 
 cJiild, why will he grasp it ? 
 
 The unconscious action of the near nervous centers pro- 
 duces a contraction of the muscles. 
 
 4. How may we strengthen the brain ? 
 
 By judicious, habitual, but not exhaustive employment. 
 The life of the brain is in change. Monotony is stagnation, 
 and stagnation is decay. 
 
 5. What is the object of pain ? 
 
 Pain is monitory in its character. It guards against danger 
 and warns us of the presence of disease, i.e., the want of ease. 
 Were it not for this, we should lose the use of the more deli- 
 
IN HYGIENIC PHYSIOLOGY. 187 
 
 cate organs. A child might gaze at the sun until its eyesight 
 was ruined. The author knew of a man who had lost the 
 sense of feeling in one leg because of the sensory nerve being 
 severed. He was constantly bruising and burning that limb 
 until he ruined it entirely. 
 
 6*. IVJiy will a bloiv on the stomach sometimes stop the 
 heart ? 
 
 By sympathy. The pneumogastric or tenth pair of nerves 
 supply the stomach and the heart. 
 
 7. How long will it take for the brain of a man six feet 
 high to receive news of an injury to his foot, and to reply? 
 
 The nervous force has been estimated to travel at the rate 
 of one hundred feet per second, although authorities vary much. 
 Taking this figure, it would require about one eighth of a 
 second.* 
 
 8. How can we grow beautiful ? 
 
 If one is penurious, selfish, or hard-hearted, his face will 
 betray the fact to every passer-by. Purity of thought and no- 
 bleness of soul, the simple habit of cherishing high and gener- 
 ous purposes, refine and spiritualize the countenance, making, 
 at last, the homeliest features to glow with a beauty that will 
 be a true "joy forever." 
 
 9. Wliy do intestinal worms sometimes affect a child's 
 sight ? 
 
 Through the action of the sympathetic system of nerves. 
 
 10. Is there any indication of character in physi- 
 ognomy ? 
 
 (See Question 8 ; also Physiology, p. 205.) 
 
 11. When one's finger is burned, where is the ache ? 
 
 All pain is in the brain. It is located, however, by the 
 mind, at the place of the injury. 
 
 * A barefooted boy steps on a thorn. If he had to wait for news of 
 the injury to be sent to his brain, and an order to be telegraphed back 
 to remove the foot, much time would be lost. As it is, with the first prick 
 the nearer nerve-centers act and order the foot off almost before the brain 
 has heard of the accident. 
 
188 ANSWJKRS TO PRACTICAL QUESTIONS 
 
 12. Is a seldom-opened parlor likely to be a healthy 
 room ? 
 
 No. It is generally ill-ventilated, and, to preserve the fur- 
 niture, kept dark, and hence damp. 
 
 13. Why can an idle scholar read his lesson and at the 
 same time count the marbles in his pocket ? 
 
 (See Physiology, p. 204, note.) 
 
 The duality of the brain may, perhaps, account for this. 
 
 14. In amputating a limb, what party ivhen divided , 
 ivill cause the keenest pain ? 
 
 When a surgical operation is performed, the most painful 
 part of it is the incision through the skin ; the muscles, carti- 
 lage, and bone being comparatively without sensation. Hence, 
 if we could benumb the surface, certain of the lesser operations 
 might be undergone without great inconvenience. This is, in 
 fact, very successfully accomplished by means of the cold pro- 
 duced by throwing a spray of ether, or of some other rapidly 
 evaporating liquid, upon the part to be cut. 
 
 15. What is the effect of bad air on nervous people ? 
 
 The nerves connect all the organs of the body. They are 
 therefore especially sensitive to a derangement in the function 
 of any organ. Bad air causes impure blood, deranged nutri- 
 tion, and hence a disturbance, of the entire economy. 
 
 16. Is there any truth in the proverb that "he who 
 sleeps f dines" ? 
 
 The proverb expresses the fact that the nourishment of the 
 brain and other parts goes on actively during sleep, they being 
 controlled by the sympathetic nerves. 
 
 17. What does a high, wide forehead indicate? 
 
 It suggests a large brain and a high intellectual power. 
 
 18. How does indigestion frequently cause a headache? 
 
 Through the action of the sympathetic system. 
 
 
IN HYGIENIC PHYSIOLOGY. 189 
 
 Jf). What is the cause of one's foot being " asleep " ? 
 
 (See Physiology, p. 225, note.) 
 
 20. When an injury to the nose has been remedied by 
 transplanting sltin from the forehead, why is a touch to 
 the former felt in the latter ? 
 
 The mind refers the sensation to the place where the nerve 
 naturally had its origin i.e., the part over which its tiny fibers 
 were originally distributed. 
 
 21. Are closely -curtained windoivs healthful ? 
 
 No. They keep out the sun and the fresh air. 
 
 22. W r hy, in falling from a height, do the limbs in- 
 stinctively take a position to defend the important organs ? 
 
 The reflex action of the spinal cord moves the limbs, into a 
 position of defense, the brain having no time to act. 
 
 23. What causes the pylorus to open and close at the 
 right time ? 
 
 The reflex action of the nerves which preside over that 
 organ. In a similar way, a tickling in the throat excites 
 coughing. 
 
 24. VTliy is pleasant exercise most beneficial ? 
 
 A chief condition of keeping the brain healthy is to keep 
 the unconscious nervous functions in full vigor, and in natural 
 alternations of activity and repose. Thus it is that (besides its 
 effect in increasing the breathing and the general vigor of the 
 vital processes) muscular exercise has so manifest a beneficial 
 influence on a depressed or irritable state of mind. The bodily 
 movement, by affording an outlet to the activity of the spinal 
 cord, withdraws a source of irritation from the brain ; or it 
 may relieve excitement of that organ by carrying off its energy 
 into a safe channel. HINTON. 
 
 25. Why does grief cause one to lose his appetite ? 
 
 Through the action of the sympathetic system. 
 
 26. W'Tiy should we never study directly after dinner ? 
 
190 ANSWERS TO PRACTICAL QUESTIONS 
 
 The blood then sets toward the stomach, and the whole 
 strength of the system is needed to properly digest the food. 
 
 27. What produces the peristaltic movement of the 
 stomach ? 
 
 The presence of the food which, through the sympathetic 
 system, acting involuntarily, sets in motion the complicated 
 apparatus of digestion. 
 
 28. Why is a healthy child so restless and full of mis- 
 chief? 
 
 Nature prompts it to exercise all the muscles in its body in 
 order to their proper development. 
 
 29. Why is a slight blow on the bach of a rabbit's neclt 
 fatal ? 
 
 The medulla oblongata is not defended with thick muscles 
 as in man. 
 
 30. Why can one walk and carry on a conversation at 
 the same time ? 
 
 (See Question 13.) 
 
 31. IVJiat are the dangers of over-study ? 
 
 (See HINTON'S Health and Us Conditions, p. 193, et seq., and CUTLER'S Ana- 
 lytical Anatomy, p. 248 ; also, Physiology, p. 331.) 
 
 Exhaustive mental labor overstrains the delicate nerve-cells 
 of the brain, and the condition of the blood-vessels of the en- 
 tire body, especially of the vital organs, is regulated, moment 
 by moment, by its changing moods. Even the supply furnished 
 the brain is subject to the same influence. Hence results de- 
 ranged nutrition, impaired circulation, and weakened brain and 
 body. Whenever we consume vital energy faster than it can 
 be replaced, we encroach upon the capital, and thus cause an 
 irreparable injury. 
 
 32. What is the influence of idleness upon the brain ? 
 
 If we would have healthy bodies we must have active 
 brains, that the streams of force may flow into every organ 
 from a full, fresh, energizing source. "The perfect health of a 
 man is not that of an ox or a horse." The proper exercise of 
 the brain is an essential element of real life. 
 
IN HYG1UXIC PHYSIOLOGY. 191 
 
 33. State the close relation which exists between phys- 
 ical and mental health and disease. 
 
 A partial cultivation of the mental faculties is incompatible 
 not only with the highest order of thought, but with the high- 
 est degree of health and efficiency. The result of professional 
 experience fairly warrants the statement that in persons of a 
 high grade of intellectual endowment and cultivation, other 
 things being equal, the force of moral shocks is more easily 
 broken, tedious and harassing exercise of particular powers 
 more safely borne, than in those of an opposite description, 
 and disease, when it comes, i3 more readily controlled and 
 cured. The kind of management which consists in awakening 
 a new order of emotion, in exciting new trains of thought, in 
 turning attention to some new matter of study or speculation, 
 must be far less efficacious, because less applicable, in one 
 whose mind has always had a limited range than in one of 
 larger resources and capacities. In endeavoring to restore the 
 disordered mind of the clod-hopper who has scarcely an idea 
 beyond that of his manual employment, the great difficulty is 
 to find some available point from which conservative influences 
 may be projected. He dislikes reading, he never learned amuse- 
 ments, he feels no interest in the affairs of the world ; and, 
 unless the circumstances allow of some kind of bodily labor, 
 his mind must remain in a state of solitary isolation, brooding 
 over its morbid fancies, and utterly incompetent to initiate any 
 recuperative movement. Dr. RAY. 
 
 34. In ivhat consists the value of the power of habit? 
 It saves the "wear and tear" of our principles. We can 
 
 perform an act a few times, though with difficulty, and then 
 ever after it becomes a habit. "We resist evil once, and thence- 
 forth it is easier to resist. We can become accustomed to do 
 good, so that the chances will all be in favor of our well-being 
 in any emergency. By so much as the power of habit is thus 
 pregnant with good, by so much is it susceptible of terrible 
 evil. 
 
 35. How many pairs of nerves supply the eye ? 
 
 (See Physiology, p. 199.) 
 Three ; the motores oculi. 
 
192 AXSWEItS TO PRACTICAL QUESTIONS 
 
 86. Describe the reflex actions in reading aloud. 
 
 The body is kept erect, the hand holds the book, the eyes 
 are directed to the page, the vocal organs pronounce the words, 
 the features express the sentiments, and the other hand makes 
 corresponding gestures yet all the time the mind is intent only 
 upon the thought conveyed. 
 
 37. Under what circumstances does paralysis occur ? 
 
 When the nerve leading to any part of the body is injured 
 or fails to keep up communications between that portion and 
 the mind. 
 
 38. If the eyelids of a profound sleeper were raised, 
 and a candle brought near, would the iris contract? 
 
 It would, by reflex action. 
 
 39. How does one cough in his sleep ? 
 
 By the reflex action of the near nervous centers. A tick- 
 ling in the throat, or some other cause, acts as the stimulus to 
 excite their action. 
 
 40. Give illustration of the unconscious action of the 
 brain. 
 
 (See Physiology, p. 225. Bead also the article " The Antechamber of 
 Consciousness,' 1 in Popular Science Monthly, March, 1888.) 
 
 41. Is chewing tobacco more injurious than smoking? 
 
 It is not only more filthy, but also more detrimental to 
 the health, as a chewer is in danger of swallowing more of 
 the poisonous constituents of tobacco, from the constant and 
 profuse excitation of saliva, which must either be swallowed or 
 conspicuously ejected. As a rule, however, modesty in respect 
 to the disposal of his "tobacco juice" does not hinder the 
 veteran chewer from bestowing his peculiar favors generously 
 and openly, and to the least conscious injury to himself. On 
 the other hand, a smoker, especially a cigarette smoker, is liable 
 to dangerous throat diseases, incurred by the heated smoke in- 
 haled from the cigarette. 
 
 4=2. Ought a man to retire from business ivhlle his fac- 
 ulties are still unimpaired? 
 
IN HYGIENIC PHYSIOLOGY. 193 
 
 No. It is always a mistake for a man who has led an ac- 
 tive life to withdraw, at once, from all occupation and to resign 
 himself to idleness. A proper degree of functional exercise is 
 as necessary to the perfect health of the mind and the brain as 
 to that of the body. 
 
 43. IVhich is the more exhaustive to the braiu, worry 
 or severe mental application ? 
 
 (See Physiology, p. 331.) 
 
 Worry is far more exhaustive of the vital forces than the 
 severest mental labor, pursued calmly and dispassionately. 
 
 44. Is it a blessing to be beyond the necessity for work ? 
 
 By no means. On the contrary, the "middle-class people," 
 those who do not suffer from actual bodily want, but who are 
 obliged to work in order to procure luxuries, or even comforts, 
 are proverbially happier than those who are born to riches, 
 and who have no incentive to systematic exertion. 
 
 4:5. Shoiv hoiv anger, hate, and the other degrading 
 passions are destructive to the brain. 
 
 The effect of anger upon the brain is to produce first a 
 paralysis, and, afterward, during reaction, a congestion of the 
 vessels of that organ. Passionate people often die suddenly of 
 faintness in the moment of white rage, when the cerebral ves- 
 sels and the heart are paralyzed. Or they may outlive this first 
 stage, only to succumb to the second, when reactive congestion 
 has led to engorgement of the vessels of the brain, and apo- 
 plexy ensues. Intensified hatred acts in a similar manner, but 
 more slowly. The effect on the brain of extreme fear is also 
 akin to that of rage, and may result in sudden death from 
 syncope. 
 
 The more common and permanent effect of fear, however, 
 is an intense irritability, followed by doubt, suspicion, and dis- 
 trust, leading toward or to insanity. From a sudden terror 
 deeply felt, the young mind rarely recovers ; never, I believe, 
 if hereditary tendency to insanity be a part of its nature. 
 
 Of these three passions, anger stands first as most detri- 
 mental to life. He is a man very rich indeed in physical 
 
194 ANSWERS TO PRACTICAL QUESTIONS 
 
 power who can afford to be angry. The richest can not afford 
 it many times without insuring the penalty, a penalty that is 
 always severe. What is still worse of this passion is, that the 
 very disease it engenders feeds it, so that if the impulse go 
 many times unchecked it becomes the master of the man. B. * 
 W. RICHARDSON. 
 
 46. Are not amusements, to repair the waste of the 
 nervous energy, especially needed by persons whose life is 
 one of care and toil ? 
 
 Yes, cheerful recreation is necessary in proportion to the 
 severity of toil and care. ^Nothing will replenish heavily-as- 
 sessed brain capital like occasional rollicking merriment. 
 
 47. Is not severe mental labor incompatible with a 
 rapidly-growing body ? 
 
 Decidedly. A rapidly-growing child should never be over- 
 burdened with mental labor. Youthful prodigies seldom develop 
 into solid, "level-headed" adults. Every extra demand upon 
 the youthful brain, beyond its normal power of healthy endur- 
 ance, is subtracted with usury from its future reserve stock. 
 
 48. How shall tve induce the system to perform all its 
 functions regularly ? 
 
 By uniformly obeying all the laws of Hygiene. 
 
 49. How does alcohol interfere with the action of the 
 
 nerves ? 
 
 (See Physiology, p. 208.) 
 
 Alcohol has the same effect upon the nerve-cells that 
 water or ashes has upon a coal fire. Apply water in small 
 quantity, and your fire will burn more slowly ; apply a large 
 enough bucketful, and it will cease to exist. When the cook 
 rakes up the ashes and covers her fire before going to bed, she 
 performs the same physical experiment as her master who 
 soothes his nerves with alcohol before retiring at night. But 
 the cook would be very late with breakfast if she trusted to 
 such a fire to cook the bacon, and the work accomplished by a 
 brain affected by alcohol is both small in quantity and inferior 
 
IN HYGIENIC PHYSIOLOGY. 195 
 
 in quality. It is as difficult to send proper messages along a 
 nerve under the influence of alcohol, as it is to fire a train of 
 damp gunpowder. J. M. HOWIE. 
 
 50. What is the general effect of alcohol upon the char- 
 acter ? 
 
 (See Physiology, p. 212.) 
 
 Alcohol exalts and excites the animal centers ; it lets loose 
 the passions, and gives them more or less of unlicensed domi- 
 nation over the whole man. " From the beginning to the end 
 of its influence it subdues reason and sets free passion. The 
 analogies, physical and mental, are perfect. That which loosens 
 the tension of the vessels which feed the body with due order 
 of precision, and thereby lets loose the heart to violent excess 
 of unbridled motion, loosens also the reason and lets loose the 
 passions. In both instances, heart and head are for a time out 
 of harmony their balance is broken. The destructive effects of 
 alcohol on the human mind present the saddest picture of its 
 influence. Memory irretrievably lost ; words and very elements 
 of speech forgotten, or words displaced to have no meaning in 
 them ; rage and anger persistent and mischievous, or remittent 
 and impotent ; fear at every corner of life ; distrust on every 
 side ; grief merged into blank despair, and hopelessness into 
 permanent melancholy. As I have moved among those who 
 are physically stricken with alcohol, and have detected under 
 the various disguises of name the fatal diseases, the pains and 
 penalties it imposes on the body, the picture has been suffi- 
 ciently cruel. But even that picture pales as I conjure up, 
 without any stretch of imagination, the devastations which the 
 same agent inflicts on the mind." RICHARDSON. 
 
 51. Does alcohol tend to produce clearness and vigor of 
 
 thought ? 
 
 (See Physiology, p. 212.) 
 
 Quite the reverse. Its effect upon the brain and nervous 
 system is strikingly opposed to clearness of judgment and log- 
 ical reasoning. See answer to preceding Question. 
 
 52. Wliat is the general effect of alcohol on the m us- 
 cles? 
 
196 A.VSWE&S TO PRACTICAL QUESTIONS 
 
 They lose their nervous control, because of the enfeebling of 
 the nervous stimulus. The muscles of the lower lip usually 
 fail first ; then the muscles of the lower limbs, the extensor 
 muscles giving way earlier than the flexors. As they come 
 still more under the depressing influence of the paralyzing 
 agent, their structure becomes temporarily deranged, and their 
 contractile power reduced. 
 
 53. Does alcohol have any effect on the bones ? The 
 skin ? 
 
 As the bones are nourished by tho blood, whatever materi- 
 ally impoverishes the blood must affect the bones. 
 
 The oft-repeated temporary relaxations of the vessels of the 
 skin, resulting from alcoholic potations, ultimately become 
 chronic, and certain parts, such as the nose and cheek, assume 
 a distinctive appearance of confirmed vascular relaxation. From 
 this deficient tonicity of the skin-vessels, the cutaneous secre- 
 tion becomes irregular ; perspiration becomes abnormally pro- 
 fuse, and sometimes is extremely acid ; and, finally, swollen 
 eruptions and scaly blotches ensue. 
 
 54. What is the cause of the alcoholic chill ? 
 
 (See Physiology, p. 210.) 
 
 55. Show how alcohol tends to develop man's lower 
 rather than his higher nature. 
 
 (See answer to Question 50.) 
 
 56. When we wisli really to strengthen the brain, should 
 we use alcohol ? 
 
 (See Physiology, p. 210 ; also, answer to Question 50.) 
 Never. 
 
 57. Wliy is alcohol used to preserve anatomical speci- 
 mens ? 
 
 Because of its antiseptic properties. These were well known 
 in ancient times, and palm wine was used by the Egyptians in 
 their most costly processes of embalming the dead. 
 
IN HYGIENIC PHYSIOLOGY. 197 
 
 58. Wliat is meant by an inherited taste for liquor ? 
 
 (See Physiology, p. 185.) 
 
 59. Ought a person to be punished for a crime com- 
 mitted during intoxication ? 
 
 Yes ; because he knows in taking the alcoholic poison into 
 his system what the logical effect will be upon his actions. 
 At the same time, the rum-seller ought in justice also to re- 
 ceive punishment for the criminal offense of aiding and abet- 
 ting such a state of moral perversion. 
 
 CO. Should a boy ever smolce ? 
 
 Never. Tobacco, in addition to its other evil effects, notably 
 stunts healthy growth. 
 
 61. To ivliat extent are we responsible for the health of 
 our body ? 
 
 To the extent of our neglect of known hygienic rules, or 
 even, in this age of easily-acquired information, to the extent of 
 our lack of knowledge of these rules. 
 
 62. Why does alcohol tend to collect in the brain ? 
 
 (See Physiology, p. 210.) 
 
 One cause is the great affinity of alcohol for water and the 
 peculiar moisture which attaches to the brain. 
 
 63. Does the use of alcohol tend to increase crime and 
 poverty ? 
 
 Even its most strenuous advocates will not deny this fact, 
 of which both statistics and common observation furnish abun- 
 dant proofs. It has been estimated that four fifths of the pau- 
 perism and crime in our country result directly from strong 
 drink. 
 
 238 1. Why does a laundress test the temperature of 
 her flat-iron by holding it near her cheek ? 
 
 The sense of warmth is very keen in the palms of the 
 hand, the cheek, etc. This sensation is much less delicate in 
 the lips and the back of the hand. 
 
198 ANSWERS TO PRACTICAL QUESTIONS 
 
 2. When ive are cold, why do ive spread the palms of 
 our hands before the fire ? 
 
 (See Question 1.) 
 
 3. What is meant by a 6i furred tongue " ? 
 
 In health, the tongue has hardly a discernible lining, but in 
 disease, the epithelium, or scarfskin, accumulates, and gives a 
 white, coated appearance. This covering is likely to be of a 
 yellowish shade when the liver is disturbed, and brown or dark 
 in blood-diseases. One's occupation often colors it. Thus it is 
 said the tongue of a tea-taster has a curious orange-tint. 
 
 4. IVJiy has sand or sulphur no taste ? 
 
 They are insoluble in the saliva. 
 
 5. What was the origin of the word palatable ? 
 
 The mistaken notion that the palate, or roof of the mouth, 
 is the seat of the taste. 
 
 6. Why does a cold in the head injure the flavor of our 
 coffee ? 
 
 Because the sense of taste is so dependent on that of smell. 
 
 7. Name some so-called flavors which are really sensa- 
 tions of touch. 
 
 . (See Physiology, p. 348.) 
 
 Taste is not a simple sense. Certain other sensations, as 
 those of touch, temperature, smell, and pain, are blended with 
 it ; and certain so-called tastes are really sensations of another 
 kind. Thus an astringent taste, like that of alum, is more 
 properly an astringent feeling, and results from an impression 
 made uj^Dn the nerves of touch, that ramify in the tongue. 
 In like manner, the qualities known as smooth, oily, watery, 
 and mealy tastes, are dependent upon these same nerves of 
 touch. A burning or pungent taste is a sensation of pain, hav- 
 ing its seat in the tongue and throat. A cooling taste, like 
 that of mint, pertains to that modification of touch called the 
 sense of temperature. HUTCHISON'S Physiology, pp. 190, 191. 
 
 8. What is the object of the hairs in the nostrils ? 
 
IN HYGIENIC PHYSIOLOGY. 199 
 
 They prevent the entrance of dust and other impurities. 
 They are also exceedingly delicate in all sensations of touch. 
 
 9. What use does the nose subserve in the process of res- 
 piration ? 
 
 It warns us of noxious gases, sifts out impurities, and 
 tempers the air before it enters the delicate respiratory organs. 
 
 10. Why do we sometimes hold the nose when we take 
 unpleasant medicine ? 
 
 (See Question 6.) 
 
 11. Why is the nose placed over' the mouth ? 
 
 As a sentinel at the gate-way to the stomach and the lungs. 
 
 12. Describe how the hand is adapted to be the instru- 
 ment of touch. 
 
 Its isolation at the extremity of the movable arm, the mo- 
 bility of its different parts, and the delicacy of the sensation 
 at the tips of the fingers, exquisitely adapt the hand to be the 
 instrument of touch. 
 
 13. Besides being the organ of taste 9 what use does the 
 tongue subserve ? 
 
 It aids in the mastication of the food and in speech. 
 
 14=. Why is not the act of tasting complete until we 
 swalloiv ? * 
 
 Because the organ of taste is located especially in the back 
 part of the tongue and the soft palate. 
 
 15. Why do all things have the same flavor when one's 
 tongue is fi furred " by fever ? 
 
 They are really tasteless. The tongue is then dry, and 
 there is no saliva to dissolve and carry particles of the food 
 into the cells covering the nerves of taste. 
 
 16. IVJiich sense is the more useful, hearing or sight? 
 
 (See Wonders of the Humo.n Body, p. 201,) 
 
 "The sight speaks more directly to the intelligence; it en- 
 larges the field of thought, it gives birth to precise notions of 
 light, of form, of extent ; and it permits the communication 
 
200 ANSWERS TO PRACTICAL QUESTIONS 
 
 of thought by conventional signs. Hearing is a necessary con- 
 dition of articulate language ; without it man lives alone, affec- 
 tion and confidence lose their most precious forms of expression, 
 and friendship can not exist. Auditory sensations act upon the 
 nervous system with more force than visual sensations. We 
 are carried away by rhythm, or it adapts itself to our ideas 
 and our passions ; music plunges us into an ideal world, and 
 holds us by an indefinable charm ; in a word, if sight speaks 
 more especially to the intellect, hearing addresses itself to the 
 affections. Sight is certainly more necessary to man than hear- 
 ing, but still the blind are generally gay and communicative, 
 while the deaf seem inclined to melancholy. As to the relative 
 influence of these two senses on the development of the intel- 
 lect, we know that the education of the deaf is slow, but may 
 be complete, while that of the blind is, on the contrary, rather 
 rapid, but is almost always very limited ; many ideas can not 
 be acquired by them, and, as has been remarked by M. Longet, 
 their minds rarely attain maturity." 
 
 17. Which coat is the white of the eye ? 
 
 The sclerotic. 
 
 18. IVJiat makes the difference in the color of eyes ? 
 
 The varying shade of the pigment deposited in the iris of 
 the eye. 
 
 19. Why do we snuff the air when we wish to obtain a 
 distinct smell? 
 
 As muscular actions are called into play to aid the sense of 
 taste, as in smacking the tongue and lips, so the act of "sniff- 
 ing," which is a mixed respiratory and nasal muscular effort, 
 is used to bring odorous substances more surely and extensively 
 into contact with the upper and proper olfactory region of the 
 nose, besides causing a larger amount of them to pass over the 
 mucous surface in a given time. MARSHALL. 
 
 20. IVliy do red-hot iron and frozen mercury (40) 
 produce the same sensation ? 
 
 The sensation in both cases is that of pain, not that of 
 touch. 
 
IN HYGIENIC PHYSIOLOGY. 201 
 
 21. Why can an elderly person drink tea which to a 
 child would be unbearably hot ? 
 
 The sensation of touch has become impaired, and is much 
 less delicate. 
 
 22. IVJiy does an old man hold his paper so far from 
 his eyes ? 
 
 "Far sight" is common among elderly people, and is reme- 
 died by convex glasses. In old age the power of adjusting the 
 crystalline lens is lost. 
 
 23. Would you rather be punished on the tips of your 
 fingers than on the palm of your hand ? 
 
 The sense of touch is much keener in the tips of the fingers 
 than in the palm of the hand. 
 
 24. What is the object of the eyebrows ? Are the hairs 
 straight ? 
 
 They serve to prevent the perspiration of the forehead from 
 running down into the eye. They act, in a measure, with the 
 eyelashes, also to screen the eye from the dust and glaring 
 light. The hairs of the eyebrows overlap each other, and are 
 set obliquely outward. 
 
 25. What is the use of winking ? 
 
 It serves to wash the eyeballs, and thus keep the "windows 
 of the soul" clean. The necessity for winking is shown by the 
 great effort required to restrain it even for a short time. First 
 discomfort, then congestion of the mucous membrane, and then 
 a profuse watering of the eye follow any attempt at stop- 
 ping this necessary act. It is an obscure sense of discomfort, 
 not usually noticed by the consciousness, that excites this move- 
 ment, the objects of which are periodically to cleanse the ex- 
 posed, part of the eyeball, to moisten and lubricate it with the 
 secretions from the neighboring glands, and probably in this 
 way to aid in the preservation of the polish and translucency 
 of the epithelial layer on the transparent portion of the globe. 
 At the same time it carries toward the inner corner all for- 
 eign bodies, and directs the residual secretions toward the 
 
202 ANSWERS TO PRACTICAL QUESTIONS 
 
 lachrymal ducts. Finally, it allows a brief but periodical rest 
 to the levator muscle of the upper eyelid. MARSHALL. 
 
 2(>. When you wink, do the eyelids touch at once along 
 their ivhole length ? Why ? 
 
 In winking, both lids move, but the upper one much the 
 more extensively. Moreover, they do not come in contact all 
 along their margins at the same instant of time, but meet first 
 at the outer corner, and then rapidly inward as far as the 
 lachrymal papillae, on which the lachrymal ducts are situated. 
 By this sweeping movement, all foreign bodies are carried to 
 the lachrymal lake. MARSHALL. 
 
 27. How many roivs of hairs are there in the eye- 
 lashes ? 
 
 The eyelashes, or cilia, consist of two, and opposite the 
 middle of the eyelid, of three rows of finely-curved hairs 
 those of the upper lid being more numerous, thicker, and 
 longer than those of the lower lid. "Those of the upper lid 
 are curved upward, those of the lower lid are curved down- 
 ward; and when the lids are brought near together, these two 
 ranges of hairs stand like so many crossed sabers, or a kind of 
 chevaux-de-frise, guarding the entrance to the eye." D ALTON'S 
 Physiology, p. 330. 
 
 28. Do all nations have eyes of the same shape ? 
 
 No. Witness the almond-shaped eyes of the Chinese. 
 "The greater or less extent of the opening of the lids makes 
 the eye appear larger or smaller; the conformation of the pal- 
 pebral muscles and the tarsal cartilages gives to the eye an 
 elongated and languishing form, as in the East, or round and 
 bold, as among the Occidentals ; but the dimensions and form 
 of the globe are the same in all countries and in all individu- 
 als." Wonders of the Human Body. 
 
 29. IVJiy does snuff-taking cause a floiv of tears ? 
 
 Because of the action of the sympathetic system. 
 
IN HYGIENIC PHYSIOLOGY. 203 
 
 30. Why does a fall cause one to " see stars " ? * 
 
 Whenever a nerve is excited in any way, it gives rise to the 
 sensation peculiar to the organ with which it communicates. 
 Thus, an electric shock sent through the eye gives rise to the 
 appearance of a flash of light ; and pressure on any part of 
 the retina produces a luminous image, which lasts as long as 
 the pressure, and is called a phosphene. If the point of the 
 finger be pressed upon the outer side of the ball of the eye, a 
 luminous image which, in my own case, is dark in the center, 
 with a bright ring at the circumference (or, as Newton de- 
 scribed it, like the " eye " in a peacock's tail) is seen ; and this 
 image lasts as long as the pressure is continued. HUXLEY. 
 
 31. Why can we not see with the nose, or smell ivith the 
 
 eyes ? 
 
 Each set of nerves is adapted to transmit to the brain a 
 peculiar class of sensations alone. 
 
 32. What causes the roughness of a cat's tongue ? 
 
 The sharpness and strength of the papillae upon its tongue. 
 This is a peculiarity of the lion tribe. 
 
 33. Is the cuticle essential to touch ? 
 
 Yes. If the cuticle be removed, as in case of a blister, 
 contact with the exposed surface produces pain rather than a 
 sense of touch. 
 
 34. Can one ticfcle himself? 
 
 It is said not ; but the author has found persons who 
 averred that they could produce this sensation upon themselves. 
 The sense, it is noticeable, is present only in those parts where 
 that of touch is feeble. 
 
 * On the occasion of a remarkable trial in Germany, it was claimed by 
 a person who had been severely assaulted on a very dark night, that the 
 flashes of light caused by repeated blows upon the head enabled him to 
 see with sufficient distinctness to recognize his assailant. But the evi- 
 dence of scientific men entirely refuted this claim, by pronouncing that 
 the eye, under the circumstances named, was incapacitated for vision. 
 HUTCHISON. 
 
204 ANSWERS TO PRACTICAL QUESTIONS 
 
 35. Wliy does a bitter taste often produce vomiting ? 
 
 The fifth pair of nerves, which supplies the lip and sides of 
 the tongue, and perceives especially sweet and sour substances, 
 ramifies over the face, and hence an acid will "pucker" the 
 features ; while the ninth pair, at the base of the tongue, which 
 is sensitive to salt and bitter tastes, is distributed also to the 
 throat, and is in sympathy with the internal organs, since it 
 seems to be "a common nerve of feeling for the mucous mem- 
 brane generally." 
 
 36. Is there any danger of looking "cross-eyed" for 
 fun ? 
 
 The muscles used thus in sport may become permanently 
 distorted. 
 
 37 Should school-room desks face a window ? 
 
 No. The light should be admitted so as to fall over the 
 shoulder upon the book. Many school-rooms are arranged to 
 accommodate the teacher only, while a blinding flood of light 
 pours directly into the faces of the pupils. 
 
 38. Why do we look at a person to ivhom we are listen- 
 ing attentively? 
 
 One sense instinctively aids another. 
 
 39. Do we really feel ivith our fingers ? 
 
 No. All sensation is in the mind. 
 
 40. Is the eye a perfect sphere ? 
 
 No. The front projects somewhat, while, at the back, the 
 optic nerve is attached like the stein to a fruit. 
 
 4=1. How often do we ivink? 
 
 Five or six times a minute. 
 
 42. Why is the interior of a telescope or microscope 
 often painted black ? 
 
 To absorb the scattered rays of light which would confuse 
 the vision. For the same reason, the posterior surface of 
 
IN HYGIENIC PHYSIOLOGY. 205 
 
 the iris, the ciliary processes, and the choroid, are covered with 
 a layer of dark pigment. 
 
 43. What is " the apple of the eye " ? 
 
 The pupil. 
 
 44. UTiatfonn of (/lasses do old people require ? 
 
 (See Question 22.) 
 
 45. Should we ever ivash our ears ivitli cold water ? 
 
 Rarely, if ever, lest we chill this sensitive organ. 
 
 4(>. What is the object of the winding passages in the 
 
 nose ? 
 
 To furnish additional surface on which to expand the olfac- 
 tory nerve. 
 
 47 '. Can a smoker tell in the darJc, whether or not his 
 cigar is lighted ? 
 
 Sight often seems to be essential to perfect what we call a 
 sensation of taste. 
 
 48. Will a nerve re-unite after it has been cut ? 
 
 Nerve-fiber seems to re-unite as readily as muscle-fiber. 
 
 49. Will the sight give us an idea of solidity ? 
 
 (See Physiology, p. 247, note.) 
 
 50. Why can a skillful surgeon determine the condi- 
 tion of the brain and other internal organs by examining 
 the interior of the eye ? 
 
 (See Physiology, p. 248, note.) 
 
 51. Is there any truth in the idea that the image of the 
 murderer can be seen in the eye of the dead victim ? 
 
 When the flame of a taper is held near and a little on one 
 side of a person's eye, any one looking into the eye from a 
 proper point of view will see three images of the flame, two 
 upright and one inverted. One upright figure is reflected from 
 the front of the cornea, which acts as a convex mirror. The. 
 
206 'ANSWERS TO PRACTICAL QUESTIONS. 
 
 second proceeds from the front of the crystalline lens, which 
 has the same effect ; while the inverted image proceeds from 
 the posterior face of the lens, which, being convex backward, 
 is, of course, concave forward, and acts as a concave mir- 
 ror. HUXLEY. The images formed upon the retina are as 
 fleeting as light itself, from the nature of the case, and dis- 
 appear as soon as the object is removed. 
 
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