336 PROCEEDINGS OF THE 



the cover can be taken o3 and the glass plates removed for 

 purposes of cleaning, without disturbing the adjustment of the 

 instrument. Mr. F. Addey, in a note on the measurement of 

 the vertical dimensions of objects, explained how it is that, in 

 measuring the depth of a microscopic object by means of the 

 fine adjustment, the apparent depth should be multiplied by 

 the refractive index of the medium in which the object measured 

 is immersed. 



Mr. A. Earland was then called upon to give his lecture on 

 " Deep Sea Deposits." Mr. Earland began by emphasising the 

 importance of the infinitely little in nature. The extinction of the 

 elephant would make little difference to the economy of the world, 

 while the extinction of a small animal like the rat would have 

 far-reaching effects. We should lose a valuable scavenger, a great 

 destroyer of foodstuffs, and the carrier of plague. In the sea 

 it is much the same, and has been so all through geological times : 

 the whales and fishes, though of great economic value to man, 

 are less important than the organisms upon which they feed, and 

 these again depend for their food on micro-organisms. Some 

 of the micro-organisms belong to geologically ancient types ; 

 there are, for instance, Silurian Lagenae which have persisted 

 until the present day. One of the greatest differences between 

 the conditions under which life exists on land and in the sea is 

 the absence of light in the sea. Except under certain very 

 favourable conditions it is practically dark at 50 fathoms, and 

 at 500 fathoms' there is nothing but a very little ultra-violet 

 light. All animals feed on vegetables — either directly, or 

 indirectly as in the case of the carnivora, which feed on herbi- 

 vorous animals. Vegetable life cannot continue without light, 

 and therefore at a depth of 50 or 60 fathoms it practically ceases 

 to exist. Animals, however, are found even in the deepest parts 

 of the ocean, and the question arises as to how such animals find 

 food. The answer to this question is " cold storage." At a 

 depth of 1,200 to 2,000 fathoms the temperature is fairly constant 

 at about 35° F. There are practically no bacteria in the deep 

 sea, and consequently no putrescence, so that the vegetable life 

 of the surface waters after death sinks to the bottom and becomes 

 food for fixed animals. Haeckel divided the creatures that live 

 in the ocean into three sections : (1) Benthos, or the creatures that 

 live on the bottom, such as flat fishes, star fishes, etc. ; (2) Nekton, 



