V] <^ 7 ^ iV \\ 'f^ CIHM/ICMH Microfiche Series. CIHM/ICMH Collection de microfiches. Canadian Institute for Historical Microreproductions / Institut Canadian de microreproductions historiques Technical and Bibliographic Notes/Notes techniques et bibliographiques The Institute has attempted to obtain the best original copy available for filming. Features of this copy which may be bibliographically unique, which may alter any of the images in the reproduction, or which may significantly change the usual method of filming, are checked below. L'Institut a microfilm^ le meilleur exemplaire qu'il lui a 6td possible de se procurer. Les details de cet exemplaire qui sont peut-dtre uniques du point de vue bibliographique, qui peuvent modifier une image reproduite, ou qui peuvent exiger une modification dans la mdthode normale de filmage sont indiqu6s ci-dessous. Q Coloured covers/ Couverture de couleur I I Covers damaged/ D □ D D fe 18.08 1 .04 19 26. 6« 26.17 1.4t> m 30.82 29.05 1.77 120 :i9.oo 36.78 2.24 144 44. y 9 42.43 2.60 An excess of 0.54 per cent, in twenty-four hours, in the evaporation of fresh water over water containing 2.6 per cent, of Na CI, may seem at first sight of little moment ; but when applied to even the present surface of the ocean— u surface so exposed over wide areas to evaporation-tending influences far higher than those brought into play in the above experiments — we raav easily conceive that an excess of this kind would be of enormous magnitude. Besides which, it must be remembered that the salt solution of the above table, contained at the commencement of the experiment, one per cent. less of solid matter than that present in the waters of the sea. As the salt solution becomes more and more concentrated, the excess of evaporation of A over B necessarily becomes higher and higher, according to the law announced above. Here then we have a self-adjus'ang phenomenon ; one of those admirable contrivances in the balance of forces, which an atten- tive study of nature reveals to us in every direction. If, other conditions being the same, any temporary cause render the amount of saline matter in the sea above its normal value, evaporation goes on the more and more slowly ; and, on the other hand, if this value be depreciated by the addition of fresh 2&ter in undue excess, the evaporating power is the more and 8 more increased ; thus aiding time, in either instance, to restore the balance. In conclusion I would observe, that the consideration of this principle may shed some further light on the geographical dis- tribution of fresh and salt-water lakes on the present surface of the globe. ^« ♦ »<*■ APPENDIX. Since the publication of the above memoir, my attention has been called by Lieutenant Maury, of the United States Navy, — Superintendent of the National Observatory at Washington, — to a chapter on the " Saltness of the Sea" in his "Sailing Directions," to accompany his admirable Wind and Current Charts. In this work. Lieutenant Maury has dev loped a new and highly ingenious theory in relation to the salt condition of the sea. When I first opened the volume, I thought that I had been anticipated in my views, but this, as shewn by the subjoined letter, containing a general exposition of the subject, is not the case. According to Lieut. Maury's hypothesis, the sea is salt in order to produce circulation ; according to mine, in order to regulate evaporation. The two, however, may not be irreconcilable. To a phenomenon indeed, of so complicated a character, more than one object is undoubtedly attached. — E. C— April 4, 1855. TO LIEUTENANT MAUEY, LL.D., Superintendent of the National Observatory, Washington, Sfe. Sfc. Sfc. DEi.It Sis, — I beg to return you my best thanks for your kind present of a copy of the sixth edition of the " Wind and Current Charts." When I sent to the Canadian Institute my note " On the Object of the Salt Condition of the Sea," believe me, I was altogether unaware of your previous publications on that sub- i' 9 ject. My paper was read and diacussed some weeks before it appeared in the Journal of the Institute ; but no notice of your highly ir.-x ant work was elicited from any of our members. As it is, > ohall remedy the omission, so far as it lies in my power to do so, by calling attention to your views in an additional note on the subject, to appear, if possible, in the May number of the Journal. "Will you allow me, however, with all due deference to one so deservedly distinguished in this branch of inquiry as yourself, to call in question the justness of some of your inferences ? If I understand the matter rightly, your hypothesis is to the following effect, viz : — That the salt condition of the sea has for its object the production of a system of circulation : this circu- lation being effected, first, by the surface water becoming Salter (and hence heavier) by evaporation, and so, sinking downwards, and giving place to the lighter water from below ; and, secondly, by the labours of coral animals, and by vital agencies generally, in removing from the water the lime and other salts. To the correctness of the latter view, I most willingly concede, although I can scarcely look upon the cause in question, as sufficiently intense to produce the phenomena of oceanic currents, according, if I mistake not, to your suggestion at page 188 of the above mentioned work. This, however, in the present state of our knowledge, is a mere matter of opinion. The merit of the enunciation belongs entirely to you ; for, although writer after writer has instanced the compensating power of the marine MoUusks and Eadiata,* in withdrawing from the sea the various salts brought into it by rivers, no one appears to have hinted, even, at the further effects due to this action. But these organic agencies are mainly referrible to the abstraction of the lime salts from the sea water : the object of the presence of the chloride of sodium— the principal saline constituent of the sea — being sought to be explained on the * And we may add that of marine vegetation also. Dr. Lvon Playfair was, I believe, the first to suggest the action of Algae in abstracting carbonic acid from the water, and thus setting free the carbonate of lime.— E. C. 10 iirsi hypothesis,* and it is here that I venture to differ from you, and to prefer my own explanation, as published in the March number of the Canadian Journal, The surface water of the sea would necessarily be rendered Salter and consequently heavier than the underlying strata, were no antagonistic influences at work ; but I tl ik we have sufficient experimental evidence to shew that the effects of evaporation are counteracted by the constant additions of fresh water which the ocean receives at its surface, and by the com- paratively high temperature of this latter (the surface) in those regions where evaporation is the most active. Comte d' Archiac in his compendium of the Physics of the G-lobe (vol. I. of his Histoire des Progres de la Greologie) has the following observa- tions : — " Les recherches faites sur la composition des eaux recueillies en mer pendant le voyage de la corvette la Bonite, ont demontre que dans 1' Ocean Pacifique, le Q-olfe du Bengale, rOcean ludien et 1' Ocean Atlantique meridional, la densite generale de I'eau prise a la surface etait moindre que celle de I'eau prise a une certaine profondeur. Une seule exception a cette regie a ete reconnue. A une seule exception pres aussi, le degre de snlure est plus prononce au fond [I * " The vapor is taken from the surface water ; the surface water thereby becomes more salt, and consequently heavier ; it therefore sinks ; and hence we have due to the salts of the sea, a vertical circulation, viz : a descent of heavier — because Salter and cooler — water from the surface, and an ascent of water that is lighter — because it is not so salt — from the depths below." — Lieut. Maury : Wind and Current Charts, 6th ed., p. 182. This view has been entertained, however, by other observers. Thus, ia reference to the Mediterranean, Sir Charles Lyell, in his " Principles of Geology," has the following remarks : — " After evaporation, the surface water becomes impregnated with a slight excess of salt, and its specific gravity being thus increased, it instantly falls to the bottom, while lighter water rises to the top, &c." But here we have to consider, how far this surface water could sink without yielding a portion of its extra salt to the surrounding water, and so rendering the whole uniform. I question altogether the probability of a vertical descent of this kind taking place in ordinary seas, at least, to any depth. Over broad areas, moreover, it would necessarily be subject to frequent and long-continued interruptions. — E. C. 11 suppose he means at considerable depths, not absolutely at the bottimi] qu'u la surface.* This view is in accordance, I believe, with the usually received opinion. f I'rom all that I have read and thought upon the sv.bject, it appears to me, that in the phenomenon of the, so to say, reversed inequalities of temperature between the surface and deep waters in the inter- tropical and polar regions, we have the main cause of oceanic movements. With all this, however, I do not mean to infer that the principle announced by you, is to be wholly disregarded in our attempts to frame a satisfactory hypothesis respecting the object of the saltness of the sea. In striving to uphold my own theory, I have done so perhaps in too exclusive a spirit. AVith regard to the origin of the saline components of sea- water, you adopt, I perceive, the views of the elder Darwin, and others, to the effect that these components have been entirely despoiled from the land, by springs and rivers, and so carried into the deep, the action continually going on But here, again, you must allow me to differ from you. My reasons for this dissent, are the following:— First, the striking pre- ponderance of chloride of sodium over the other salts in the sea-water ; whereas, amongst the saline matters generally present in river-water, it by no means occupies a veiy con- spicuous place. But even if the sea were fed by brine-springs instead of rivers, my argument would still hold good; for in nine cases certainly out of every ten, these brine-springs would be but returning to the ocean, what, in former geological epochs, * " The reaultg of the < leniical examination of samples of sea-water col- lected during the voyage of the corvette la Bonite, have shewn, that, in the Pacific Ocean, the Gulf of Bengal, the Indian Ocean, and the South Atlan- tic, the general density of water taken from the surface was less than that taken from a certain depth. Only a single exception to this law was noticed. With little more than a single exception also, the degree of saltness was greater at great depths than at the surface." See also Comp. rend. vol. vi. p. 616, from which the above is quoted. — E. C. f Theoretically, the -surface water, owing to evaporation, should be slightly cooler than the stratum of water immediately below it. I allude, of courso, to warm and temperate seas. — E. C. the ocean had rendered to the land. Fowues's assertion, quoted in your note at page 170,* appears to me to be altogether untenable, or at leayt without true bearings on the point at issue. Lakes, so peculiarly-conditioned as those of which he speaks, have evidently not been rendered salt (in the common acceptation of the term) by the rivers which How into them, but have been salt from the beginning — as portions of ancient seas cut off from the main ocean by geological changes. Secondly, according to this view, the sea must at one time have been far less salt than at present, and have gradually become Salter and salter ; an inference, the assumption of which is scarcely warranted on palaeontological data.f This objection might be met, however, by assuming that marine life was created, as a compensating agent, so soon as the sea attained to its * " The case of the sea," says Fownes, " is what occurs in every lake into which rivers flow, but from which there is no outlet except by evaporation. Su ;h a lake is invariably a salt lake. It is impossible that it can be other- wise ; and it is curious to observe that this condition disappears when an artificial outlet is produced for the waters." — Lieut. Maury. To this, I reply that, owing to the comparatively small amount of chloride of sodium in ordinary river-waters, a lake of this kind, if originally fresh, would become silted up by deposition of carbonate of lime, &c., long before it could possibly exhibit the composition of the ocean. An originally salt lake would necessarily become fresh in course of time, if river-waters were constantly poured into it, and an outlet also provided by lower levels to the sea. If we place at three difForent levels, an empty vessel, a vessel con- taining a salt solution, and one filled with ordinary water, this latter occupying the highest level, and connect the three by strips of filtering paper or a few cotton threads to act as siphons, the contents of the middle vessel (hero representing the salt lake) will be gradually replaced by the water from above, and transferred to the under vessel. Where no outlet is provided, local conditions, on the other hand, as in the case of the Dead Sea, may modify to a marked extent the original composition of the water. — E. C. f I am quite aware that the study of Fossil Ichthyology offers some slight support to the view mentioned in the text ; but this, at the best of doubtful acceptation, is, on the other hand, completely outbalanced, if we take into consideration the immense numbers of radiated animals, brachiopods, cepha- lopods, and other types, which preceded fish-life, and which were undoubt- edly marine. — E, C. prortciii saltnosa, ami nut bcfon'. 1 place, tborofbre. no great stress upon it. Finally, may we not legitimately seek to ascertain, why chloride of sodinni should have been chosen by Divine Wisdom, in preference to other salts, as the chief constituent of the Bolid matter of the sea. Apart from its manifold economic applications, I feel assured that some abstract principle is involved in its selection. I have been trying to device some experiments to elucidate this, but hitherto, witliout success. May not, however, the primary caur-e of its selection, lie in the extremely slight variation which it exhibits in regard to its solubility in water of very different temperatures ? Trusting that you will look upon these observations, as they are meant, in the light of a friendly interchange of opinion, J am, dear Sir, Most truly yours, EDWAED J. CHAPMAN. Univehsitt College, Toronto, Canada West, April 3, 18 55. 5 ADDITIONAL NOTE. Since the above was in type, I have obtained, somewhat accidentally, a sight of the English edition of Grustav Bischof's Chemical Greology, published by the Cavendish Society of Loudon. From this able work, which differs very materially, as stated by its author, from the original German edition, I have extracted the following remarks in further illustration of my subject. With regard to the origin of the saline ingredients of sea-water, it will be seen, that Professor Bischof's opinion coincides entirely with my observations as expressed at page 12 ; and although partly agreeing, in reference to vertical cir- culation, with Lieutenant INIaury, his views are still, in the main, even here, essentially in accord with mine. — E. C, April 17. 1855. 14 I. Oriijiii of tilt- xaliiif coiiKtittuuis Iff' the S/'a, "The origin of t be large iirnount of saline ingiedieiiti< containeii iii sea- water, hft8 Innf? been an object, of attention. More than a century uj^o, Halloy (Philos. Transact. Xo. 044) fiidenvouroil to show that it is due to the water which the sea received from rivers being ahvavs raoro or less im pregnated with salts, while in that which it lo.«es by evaporation tliere are none of these present. In the German edition of nay ' Geology ' I alao adopted this view. At that time only two analyses of river water existed ; there was consequently no sufficient data from which the amount of salts which are conveyed into the sea by rivers could be estimated. Misled by the large amount of chloride of sodium contained in mineral springs, I over estimated the proportion in which it exi.ata in rivers. Sulphates are carried into the sea in much greater quantities than chlorides. " From the salts contained in stratified formations we cannot derive any explanation as to the salts contained in the water of the sea, inasmuch as the former have merely been deposited from the sea. '* Throughout the whole sedimentary period, from the transition rocks to the tertiary formations, rock-salt has been deposited, though not certainly everywhere. Since it can only be supposed ttiat such deposition took place from the sea, immense quantities of salt must have been withdrawn from it in this way. " From beds consisting of pure rock-salt, very little is carried back to the sea by rivers. The chloride of sodium which is convoyed to the sea, can therefore only be derived from that which is contained in small quantities in rocks, and which is dissolved out by the water percolating tlirough them. It is impossible, however, that this can be an equivalent for the important beds of rock-salt which have separated from tlie sea throughout the whole sedimentary period. During this period, thert'fore, the quantity of chloride of sodium in the sea cannot have increased, but must have decreased, in the same proportion as its deposition in the form of rock salt, inaccessible to the percolating water, exceeds the quantity derived from crystalline rocks. ******** "From the foregoing considerations it follows that the solid constituents of sea-water have, since the Creation, undergone a constant circiibiliun, which still contibues and always will continue. We cnn, however, come to no other conclusion than that the fixed constituents, which are at present held in sea-water, were always present, although perhaps in different pro- portions." — Dr. Gufifiiv Bixrhnf. 11. "By evaporation the water at the surface of a sea must become concen- trated. Were a sea a column of water in a state of rest, it would present a proe;ressive incrp.nsi> ofir^ valine foiistitiiont? from rlu; -^nrfact^ downwards. So liir (It)WMWaidH. liuwi'Vci, um th.- inuvt'iiitiiiM of tlio wavPK t'ltontl, ihe piirtu'lfH of watt'r uro iiiii>-;leil t<)s;ei!i.T ; tliua far, llien-lbre, tlie proportion of'aaline constitiiontH i« cqiml. If, however, that should be increased ever so little, ill conspqucnce of »>viiporatioii, tho water which has heroine specilicnllv heavier, will sink beneath tlin spccilifHlly lijihter water of the tranquil sea. This is sufBcient to explain the f,M-eafcr proportion of saline constituents in the lower strata of the waters of the Mediterranean. '* This phenomenon is, however, intimately connected with the circum- stance, that the sea in question receives less water through the medium of rivers and rain than it loses by evaporation. * * * In the oeean the relations are different. If the particles of water at its surface become concentrated and sink, such water, rich in saline constituents, must still, by means of currents, be constantly tnin^^linp with water containing a small quantity of them, and, in this way, oiiinot collect in any one place. More- over, the ocean, taken in its whole extent, inalwiiys receiving as much water from rivers, as well as by means of rain and snow, as it loses by evaporation. Only in inland seas, or at least in such as merely communicate with the ocean by narrow channels, and which, therefore, take no part in the great currents afTecting the latter, can an increase in the saline constituents in proportion to the depth take place, in consequence of the causes above- mentioned. " Hy the continuance of evaporation in the Mediterranean, Lyell remarks, additional .supplies of brine are annually carried to deep repositories, until the lower strata of water are fully saturated, and precipitation of continuous masses of pure rock-salt, extending perhaps for hundreds of miles in length, might eventually take place. In reference to this, it must be observed, that even if by evaporation the surface water should become quite saturated with .salt, this saturated Huid cannot reach the deeper parts, quite unmixtd with water poorer in salt. Even if no wave motion took place, such an intermix- ing would still rnsnlt, and more , so if the sea be in violent agitation. At jiresent, therefore, certainly no rock salt is deposited on the h /ttom of the .Mediterranean, nor does this sieein to be Lyell's opinion.*'— />ir. O'lcslao Bischof. *^ It i.s dup to Lieiueuaut Maiirv. to state, that in a letter received from hini at this^ last moinent (April 20th), he men- tions the abandonment of his view.s re.specting the origin of the salt in sea water, some time after the publication of the last edition itf his work. — E. C. I