CHAP. x.J CONTINUITY OF THE CHALK. 497 



chalk element is of no more importance than is the 

 original British element in our own English people." 



Mr. Prestwich thus fully admits the high pro 

 bability of the ' continuity ' for which we contend. 

 The last question which he raises in the sentence 

 quoted is one of enormous difficulty, which we have 

 as yet no data to solve. It is perhaps not very much 

 harder, however, after all., than the problem in ethno 

 logy which he has selected as an illustration. 



Several other very important questions bearing 

 upon the conditions of the ocean at great depths, 

 occupied the attention of the naturalists in scientific 

 charge of the dredging cruises of the 'Lightning' 

 and c Porcupine. 5 An assistant versed in the methods 

 of chemical and physical research accompanied the 

 vessel on each occasion. A son of Dr. Carpenter, 

 Mr. William Lant Carpenter, B.A., B.Sc., went on 

 the first cruise with Mr. Jeffreys. Mr. John Hunter, 

 P.C.S., a promising young chemist, since deceased, 

 accompanied me to the Bay of Biscay, and Mr. Her 

 bert Carpenter, a younger son of my colleague, was 

 our companion during the third long cruise in the 

 E&roe channel. 



The specific gravity of the water was taken at 

 each station, and in the serial soundings the water- 

 bottle was let down to the intermediate depths and 

 the water carefully tested. The differences observed 

 were very slight, but they were as a rule confirmatory 

 of Professor Eorschammer's opinion that Arctic water 

 contains less salt than the sea-water of temperate 

 and intertropical regions. 



As I have already mentioned (page 4(>), organic 

 matter in appreciable quantity was detected by the 



K K 



