TRANSArXIONS OF SECTION D. 



747 



quantity of oxyjjen absorbed ixt iiori 

 should niiij.'i', accordiiif.' to I'rofcssor 



certain di'iitlisnre reaclu-d Ptovopod sliells arc dissolvi-il and disappear from the flcn- 

 hottoiu, and lit Cfrlain fiirtlicr dt'j)tli,M (UohiijiriiKi .slidls .><iill'or the .saiuo fato, 

 I'rnf'c.iHor Kittiiiar holds the o|iiniiiM tluit tin' ^oliitiuii is iint diif to the prt'sciiot' of 

 free aciil, but to tin- sulveiit action of tlif sea-water itself, which will, even when 

 .ilkaliiie. take np additional carlionate of lime if .suilicient time Im given. Thus 

 til.' aiiidimt of carbonic acid normally present throiijrhout the ocean cannot bo 

 iiiiiiiicid til lite; but, accordiiiL' to the I'rofessoi-, there must beintht> dejtths of the 

 oci'ftii niiniorons bodies of richly carbonated water, for he re^mrds the princi])al 

 .•iiiimly of carbonic acid to the sea-water as derived from \(ilcanic spi'in^rs and 

 (liM'liinyes iftsuinfr from the ocean-bed, the (|Uiintity derived from the decay of 

 marine plants ami animals beini; insifjniticant in comparison with this. Possibly 

 til,' ' ( 'hallenijrer,' when it dredp'd from deep water oil" the Azores immense 

 (iiiiiititit's of dead and hlackeneil coral, enconntcred an area \\hich had thus been 

 vi-iti'il by a carbonic acid discharpj. 



W'itli re}.'ard to the ahsorheil o.\ye-en and nitroijen, the theoretical maximum 



normal surl'ace-pri'ssure by a litre of sea-water 

 Dittmar's experiments and calculations, from 

 ^•IS c.c. ill cold rejrions at 0° (!. to 4'o(i c.c. in tlie tropics, with a temperature of 

 30 C. The results ex]ierimentaliy olitained from samples of surface-water collect e<l 

 drinp the voyajre diil'er considta-ably in detail from the calculated estimates from 

 various causes explained, and e.'^ppcially because of the redact i(ni of the anioumt of 

 o.'Tffeiiliy oxidation and respiration. The main and almo.st .sole .source of the nitro- 

 ;.vii"and oxycen present in deep-sea water lies in the atmosjiliere and is ahsorljedat 

 tlif .surface, its quantity beiufr thus depi'iuh'nt on surface conditions of temperature 

 and pressure and not those of the depths. A i^iven quantity of water, havinj,'- absorbed 

 it* oxyfren and iiitrofren at the surface, may be supjiosed to siidv unmixed with sur- 

 I'nundin;? wat"r to the depths. During the process its amount of contained nitrofjen 

 ri'mainscon.stant, -whilst its oxyfren-sup])ly becomes prradually diuiinished, owinfr to 

 tiu^ process of oxidation, which in the depths jro on without compensation. That 

 till' amount of absorbed oxygen pi-esent in .sea-water diminishes with tlie depth 

 liad beeii shown already by JNIr. Lant Carpenter's experiments. It is not yet 

 pn-,*ible to formulate in any precise terms the relation between the depth and the 

 diminution of the oxygen present, but Mr. J. Y. Buchanan's previous conclusioTi 

 t'.iat a minimum of oxyiren is attained at a depth of about 800 fathoms is not con- 

 firmed by the summing up of the whide of the evidence now available. Tiiis rtsult 

 i> not without biological siu:nificance, since the existence of this supposed zone with 

 a minimum of oxygen has heen used as an argument in favour of the occurrence of 

 especiidly abimdant life at this depth below the ocean-surface. 



Professor Dittmar tinds that there is nothing characteristic of bottom-waters as 

 such ill regard to their absorbed gases, nothing to distinguish them fi'oni waters 

 from intermediate depths. This, it seems to me, is not quite what might have been 

 expoctod, as the concentration of the food supply, and consequently of life, on the 

 actual Ixittom might have led to a dill'ereiit result. 



If there were absolute .stagnation of tiie -water at great depths the oxygen might 

 l)e reduced there to zero, but the fact that in no case has oxygen bi'en entirely 

 absent from any sample of deep-sea water examined proves that a certain motion 

 and change must occur. The smallest amount of oxygen found at all was in a 

 sample of water from a depth of 2,S7r) fathoms, and amounted to O-fio c.c. per litre 

 o;i!\,a result long ago published liy 3Ir. Buchanan. ]'>en this, however, may well 

 be ,«ullieient to support life, since Humboldt and Provencal' found that certain fish 

 ciuld breathe in water containing' only one-third of that quantity of oxygen per 

 litre. In another sarajde, from 1,045 fathoms, it was 2*04 c.c. On the other hand, 

 as much as 4'055 c.c. was found in a sample from 4,575 fathoms, and 4'8f) c.c. in 

 one from 3,025. Most remarkable, in one instance water from a depth of only 300 

 fatiionis yielded only 1"G5 c.c. of oxygen. Professor Dittmar admits that there was 

 no lack of anomalous results, some, no doubt, due to some extent to imperfection in 

 tl;e apjiaratus employed in collecting the water. 



' ' Sur la Respiration des Poissons,' Joiirn. do P/ii/.siqtic, de Chimie ct d'lTLitmre 

 ^'aturrlh-, t. Ixix., October 1809, p. 2(58. 



¥ IX 



^i 



