BY THE rEESIDENT. 185 



been partly onumorated above." He mentions amoni^ the formcT 

 five species of fish (one of a new gemis) discovered in the 

 ' Challenger ' Expedition at depths of from 675 to 2040 fathoms, 

 besides several Mollusca and Crustacea.* 



Some land-sings and molluscs (e.g. Geomalaciis maculostis and 

 Achat ina acicula) are also blind. On the sea-shore and in shallow 

 water most bivalves, as well as all the species of Chiton, are eyeless. 



Some deep-sea animals are brightly and deeply coloured. In the 

 'Challenger' Expedition shrimps "of an intense bright scarlet 

 colour" were obtained in very great abimdance ; and many holo- 

 thurians or " sea-cucumbers" were of a " deep purple " hue. The 

 same observation occurred to me in the ' Porcupine ' and ' Travailleur ' 

 Expeditions. 



6. Temperattjee. 



The highest temperature of the sea-bottom observed in the 

 < Challenger' voyage at depths over 1000 fathoms was 50^-5 Fahr., 

 in 2550 fathoms; the lowest was 32°- 1, in 1950 fathoms. The 

 average bottom-temperature at great depths does not much exceed 

 the freezing-point ; but life does not appear to be affected by that 

 cii'cumstance. In the Arctic Expedition of 1875 I found an 

 abundance and variety of animals in icy cold water. 



7. Depth. 



The average depth of the ocean between latitudes 60° N. and 

 60° S. is nearly three miles, or 2500 fathoms. The greatest depth 

 which has been ascertained by sounding is five miles and a quarter, 

 or 4620 fathoms, and occurs in the j^orth-west Pacific Ocean ; it is 

 nearly equal to the height of Mount Everest, the highest known 

 mountain, the relation being in the proportion of 27,720 to 

 29,000 feet. 



8. iNEQITALITrES OF THE SeA-BOTTOM. 



The operations of the Telegraph Construction and Maintenance 

 Company have materially added to our knowledge of the shape and 

 contour of the floor of the ocean. They have shown us that the 

 bed of the sea is quite as uneven as the surface of the land, and 

 that it represents the same mountains, hills, gorges, and valleys, 



• 111 the Norwegian Xorth- At! antic Expedition of 1878, a fish was taken at 

 the depth of 1280 fathoms (nearly a mile and a half), which is now described by 

 Mr. CoUett, and said to have been of a uniform bright red colour, with well- 

 developed eyes. It was not only living when brought up in the trawl, but was 

 kept some time alive in a tub of sea- water. It was about a foot in length. 

 Temperature at bottom between 34° and 35° Fahr. 



