Feb. 22, 1872J 



NA TURE 



3^5 



Sierra Leone, and the soundings and other observations 

 were continued till she reached Havanah, April 13, 1871. 



The papers, together with the various specimens, were 

 placed in the hands of Professor Henry Draper, of the 

 New York University, for examination. His report com- 

 mences by stating " that much attention has recently 

 been given to deep-sea researches in consequence of the 

 investigations made by the United States government on 

 its coast, and by Dr. Carpenter. Mr. Gvvyn Jeffreys, and 

 Prof. Wyville Thomson, in the North Atlantic and 

 Mediterranean Sea. Not only have many of the facts so 

 ascertained been corroborated by this voyage of the 

 Mercury, but the commissioners, by authorising it, have 

 added much that is new and interesting to our knowledge 

 of the physical condition of the deep sea." 



Then follows a discussion of the barometric variations, 

 in which it is show that they were very small in crossing 

 the ocean, the minimum being only -^^ below, and the 

 maximum j%-, above the mean. In a general manner the 

 pressure increased on nearing the .\merican coast. 



The currents varied from south near the African coast 

 by south-west to west near the American coast, and their 

 velocity was on an average above half a knot. 



Some general remarks on the sounding apparatus 

 (Brook's detaching apparatus) and water-collecting 

 cylinder are next made, attention being more particularly 

 directed to the incorrect conclusions that the latter is apt 

 to lead to. " The constitution of the water as it exists at 

 great depths is not correctly represented by the sample 

 thus obtained. A considerable portion of the gases 

 dissolved therein may escape under the relief of pressure 

 as the cylinder is drawn to the surface, and hence 

 examinations of such samples as regards their gaseous 

 ingredients are liable to be deceptive. Even the saline 

 ingredients will sufler disturbance when they are held in 

 solution by gases that will thus escape ; for instance, this is 

 the case with carbonate of hme." Table iv. shows the 

 specific gravities of the samples of sea water from the 

 surface and at various depths to 420 fathoms ; Table v., 

 the air temperature between Sierra Leone and the Florida 

 capes ; Table vi., the temperature of the air, sea surface, 

 and of the water at various depths. The thermometer 

 was of Six's form, without index error when compared 

 with a standard Kew instrument, but not protected on the 

 Miller-Casella plan. 



A diagram of the bed of the Atlantic Ocean at the 

 twelfth parallel of latitude is introduced, based on fifteen 

 soundings. It shows that " parting from the African 

 coast the bed of the ocean sinks very rapidly. A couple 

 of degrees west of the longitude of Cape Verde the 

 soundings are 2,900 fathoms. From this point the mean 

 depth across the ocean may be estimated at about 2,400 

 fathoms, but from this there are two striking departures — 

 first a depression, the depth of which is 3,100 fathoms, 

 and second, an elevation at which the soundings are only 

 1,900, — the general result of this being a wide and deep 

 trough on the African side, and a narrower and shallower 

 trough on the American. It may be that this peculiarity 

 is a result of the river distribution on the two continents 

 respectively, there being, with the exception of the Senegal 

 and Gambia, no important streams on the African side, 

 whilst on the American there are many, and among them 

 pre-eminently the Orinoco and the Amazon, these vast 

 rivers canying their detritus far out to sea and helping to 

 produce the configuration of the ocean bottom in question. 

 However this may be, it is doubtless through these deep 

 troughs that much of the cold water of the north polar 

 current finds its way." 



" In accordance with this we perceive, on examining the 

 temperature of the water after the African verge of the 

 greater or eastern sea trough is reached, that there is a 

 difference in temperature between the surface and that at 

 a depth of not more than 200 fathoms exceeding 25'' in 

 many cases. This decline of temperature increases as 



the depth increases, one observation giving an additional 

 fall of 4° at an additional depth of 200 fathoms. It is 

 not, however, intended to affirm that the mass of cold 

 water is restricted to these deep troughs, since even in the 

 West India seas at similar depths low temperatures are 

 observed, and this though the, heat of the surface water 

 had become very much higher. In those seas while the 

 surface temperature was 84" the thermometer at depths 

 of 400 and 500 fathoms marked 48° ; and these it must be 

 remembered were the indications of an uncompensated 

 instrument which was bearing a pressure of at least half a 

 ton on each square inch of its surface, and hence 

 registering degrees that were higher than the truth. This 

 accords with the observation of Mr. Barrett that in the 

 deepest parts of the sea near Jamaica there exists a 

 temperature not far above that of the freezing point of 

 fresh water." Accompanying these remarks is a diagram 

 showing the curves representing the temperature of the 

 air, surface of the water, and deep water during the 

 voyage, and that is followed by a diagram of the specific 

 gravity of surface and deep water. 



" The general conclusion which may be drawn from 

 these results as to temperature and specific gravities is 

 that there exists all over the bottom of the tropical Atlantic 

 and Caribbean Sea a stratum of cold water — cold since 

 its temperature is below 50°. This is the conclusion to 

 which Dr. Carpenter has come as respects the Atlantic in 

 higher north latitudes ; and in this important particular 

 the cruise of the Mercury must be considered as offering 

 confirmatory proof of the correctness of the deductions 

 drawn from the cruises of the Lii^htning and Porcupine" 



" There are reasons for supposing that, so far from this 

 water being stagnant, its whole mass has a motion towards 

 the Equator, whilst the surface waters in their turn have a 

 general movement in the opposite direction." 



An analysis of the gaseous ingredients was not 

 attempted, because the specimens had been kept too long 

 and for other reasons that are specified ; but in relation to 

 organic matter it is stated : " I made some examinations 

 of the organic matter contained in these waters both by 

 incinerating the solid residue and by the permanganate 



test It needed no especial proof that organic 



matter was present in every one of these samples, for the 

 clearest of them contained shreddy and flocculent 

 material, some of them cjuantities of sea- weed in various 

 stages of decomposition. With these vegetable substances 

 were the remains of minute marine animals. As bearing 

 on this subject I found on incinerating the solid residue 

 of a sample of water taken from 200 fathoms, that the 

 organic and volatile material was not less than 1 1 per 

 cent, of the whole. Though the quantity of organic 

 substance diminished as the .structure under examination 

 was deeper, there still remained a visible amount in the 

 water of 400 or 500 fathoms. It is probable therefore 

 that even at the bottom of the ocean such organic sub- 

 stance may exist, not only in solution aflbrding nutriment 

 to animals inhabiting those dark abysses as Prof. Wyville 

 Thomson has suggested, but also in the solid state. 

 Plants of course cannot grow there on account of the 

 absence of light." 



" In order to determine whether any hitherto unknown 

 element existed in these waters, I subjected the solid 

 residue to examination with the spectroscope, volatilising 

 the substances by the aid of a voltaic current and 

 induction coil. A careful examination did not reveal the 

 presence of any spectral lines other than those belongirig 

 to the well-known elementary substances in sea-water." 



" The specimens of the bottom, obtained by attaching 

 to the sounding line quills or wooden tubes, I have 

 transmitted to Dr. Carpenter, who has kindly consented 

 to examine them. In a letter recently received he says, 

 ' As far as I can see they consist of the ordinary Atlantic 

 mud, chalk in process of formation, with the ordinary 

 types of deep-sea foraminifera.' " 



