xlvi THE VOYAGE OF H.M.S. CHALLENGER 



During Otto Torell's expedition to Spitsbergen in 1864, a great number of creatures 

 were taken at a depth of 1000 to 1400 fathoms in the " Maclean nets." They included 

 Rhizopoda, Bryozoa, Sponges, Annelids, Crustacea, and other forms. in subsequent 

 expeditions to Spitsbergen, creatures were frequently secured from a similar 

 depth. 1 



In 1865 a paper by Professor Forchhammer of Copenhagen on the Composition of 

 Sea- Water in different parts of the Ocean was published in the Philosophical Transac- 

 tions, 2 recording the result of twenty years of patient work, and its publication made 

 an era in the history of ocean chemistry. Forchhammer worked under great disadvant- 

 ages ; his samples of water were brought home by seafaring men from different parts 

 of the world in corked bottles, and they were necessarily all taken from the surface or 

 immediately beneath it. Forchhammer did not attempt to determine quantitatively 

 all the elements that occur in sea water, but confined himself to the very accurate 

 estimation of the principal components, viz., chlorine, sulphuric acid, magnesia, lime, 

 potash, and (by difference) soda, Although his methods have since been improved on, 

 all the analyses were models of care and accuracy, and all his results have been confirmed 

 and extended by Professor Dittmar's elaborate research, carried on under conditions so 

 immensely more favourable on the water samples carefully collected on board the 

 Challenger. Forehhammer's grand conclusion is that although the salinity of sea 

 water may and does vary within certain limits, yet if samples be taken in all parts of 

 the open sea, avoiding the vicinity of land and the mouths of large rivers, the proportion 

 of each constituent to the total salts will be found to be the same everywhere. The 

 differences in surface sea water then are merely differences due to dilution and con- 

 centration. 



In 1867 Count L. F. de Pourtales commenced, in connection with the United States 

 Coast Survey, a series of deep dredgings on the margin of the Gulf Stream. Working in 

 the U.S. Coast Survey steamer " Corwin," he dredged down to a depth of 350 fathoms ; 

 and in the following year he resumed the work in the same place in the U.S. Coast 

 Survey steamer "Bibb," and dredged successfully in 510 fathoms, finding animal life 

 exceedingly abundant. Although a great part of the collections made by Pourtales 

 were lost in the great fire of Chicago, many new species have been described and brought 

 under the notice of zoologists, and the wide bearing of the new facts obtained were 

 comprehensively discussed by Professor Louis Agassiz, who took part in these explorations 

 with Pourtales. 3 



It has always been supposed that costly appliances and a large crew are absolutely 

 necessary for successful dredging in water of any great depth. G. O. Sars indeed had 

 worked down to 300 fathoms in a small boat manned by three men, off the Lofoten 



1 Zetitchr.f. wiss. Zool., Bd. xx. p. 457, 1870. * Phil. Trant., vol. civ. pp. 203-262, 18(55. 



3 Hull. Mm. Comp. Zofil., Cambridge, U.S.A., 1868 and 1869. 



