62 ABSTRACTS OF LECTURES. 



waters were entirely neglected as being beyond the scope of in- 

 vestigation. Shortly after, however, the question as to whether 

 life could exist on the deep sea bottom was accidentally, 

 though definitely answered on several occasions, notably when 

 the broken end of the Atlantic cable was dragged up encrusted 

 with organisms. In 1873 the " Challenger," with a large 

 scientific staff", under the guidance of Sir Wyville Thompson, 

 was equipped by the British Government to explore the deeper 

 waters with a view to scientific discovery. The results con- 

 tained in the 36 vols, of the " Challenger " report, though in 

 view of recent discovery not quite up to date, show what a 

 tremendous field for research has been opened up. Subse- 

 quent expeditions have been undertaken by the " Porcupine " 

 and " Albatross," and the work is at present being carried on 

 by the United States Fisheries Investigation and the Indian 

 Marine Survey. 



As is well known xeth of the earth's surface is under 

 water. At places the depth of water is 4,700 fathoms — almost 

 five miles — while the average depth is 1,877 fathoms. There 

 are a few mountain ranges on the sea-bed, and several 

 isolated peaks rising towards the surface. The sides of the 

 ocean basin are not steep, being inclined at about 4°, except 

 from oceanic islands, and at the Bermudas where the slope is 

 about 20° to a depth of 2,000 fathoms. 



The physical conditions of the deep-sea bed are necessarily 

 exceptional. The deeper the sounding taken the nearer does 

 the temperature approach 4°C. Sunlight never penetrates 

 lower than 100 fathoms, and blind Isopods are found at 55 

 fathoms in the Lake of Geneva. With this decrease of light 

 and heat there is a tremendous increase in pressure, being as 

 much as one ton per square inch per 1,000 fathoms, or 166 

 atmospheres. There is a slight current from the poles along 

 the bottom towards the equator, but it is so slow as to be 

 imperceptible to animal life. The surface of the sea-bed is 

 perfectly even, any crevices being levelled up by the deposition 

 of oozes, either pteropod, foraminiferal, or radiolarian, accord- 

 ing to depth. At extreme depths it is merely a red clay. To 



