4 THREE CKUISES OF THE " BLAKE." 



the ocean is played by the pelagic forms which^ after death, 

 slowly find their way to the bottom and form at the pre- 

 sent day deposits in every way similar to those of the chalk. 

 Mr. Murray has, however, from the more extended explorations 

 of the '• Challenger," clearly proved that the deposits going on 

 beyond the continental platforms, at great depths in the oceanic 

 basins, find no analogue among the stratified rocks with which 

 we are acquainted. Professor Agassiz and Sn WyvLlle Thom- 

 son also soon became convinced, as a result of their experience 

 in deep-sea explorations, that the oceanic basins were of great 

 antiquity and have always existed, and that the animals found 

 at great depths existed under conditions which have remained 

 unchanged from a remote period of time. 



Sir William Thomson, who became interested in deep-sea 

 soundings from his connection with the la^ang of submarine 



Fig. 2. — Sir William Thomson's Soundiug Machine. (Thomson.) 



cables, made a trial in 1872 of a machine he had devised 

 for sounding with a piano-wire line. This machine (Fig. 

 2), and his first use of it in sounding, is thus described by 

 him : " I sounded from the ^ Lalla Rookh,' with a lead weight 

 of thirty pounds, hung by nineteen fathoms of cod-line from 

 another lead weight of four pounds, attached to one end of a 

 three-mile coil, made up of ends of piano-wire spliced together 

 and wound on a light wheel about a fathom in circumference, 

 made of tinned-ii'on plate. The weight was allowed to run 

 directly from the sounding-wheel into the sea, and a resist- 

 ance exceeding the weight in water of the length of the wire 



