PHOTOGRAPHY OF OCEAN FLOOR — LAUGHTON 321 



framework. Some such form of indicator is an important part of any 

 equipment which is required to be lowered to the bottom of the deep 

 sea, since it is impossible, in the presence of the additional tension due 

 to up to 3 miles of wire hanging in the water, and the variations in 

 tension due to the rolling and pitching of the ship, to feel the change 

 in tension on the wire when the camera reaches the bottom. The 

 pinger normally emits signals at a slow rate while the camera is in 

 midwater, but when it touches bottom, the rate is increased. 



The camera is triggered by a weight, combined with a small sampler, 

 that is suspended below the camera. ^Vlien this touches bottom, the 

 flash, synchronized with the shutter opening, is triggered, the pinger 

 signals the surface, and the film is moved to the next frame. The 

 operator can immediately raise the wire several fathoms so that the 

 camera itself never touches bottom. After a minute or so another pic- 

 ture can be taken and the process repeated. A series of pictures can 

 thus be taken while the ship drifts. In this way a pliotogi*aphic profile 

 can be made of such deep-sea features as seamounts or the edges of 

 abyssal plains. Any standard black-and-white or color film can be 

 used, and, if desired, stereoscopic pictures can be taken by using two 

 separate photographic units. The underwater camera is shown in use 

 on R.R.S. Discovery II in plate 1, figure 2. 



THE RESULTS OF PHOTOGRAPHIC EXPLORATION 



During the past 3 years many hundreds of photographs of the sea 

 floor, at depths varying from a few fathoms to nearly 3,000 fathoms, 

 have been taken hj workers at the National Institute of Oceanography. 

 The photographs have an immediate interest in revealing for the first 

 time a part of the earth's crust never before seen by man but their full 

 scientific value cannot be realized unless they are related to the broader 

 environment in which they are taken. Thus they should be taken in 

 conjunction with a topographic survey of the area and with system- 

 atic sampling of the bottom by such means as coring and dredging, 

 so that the details revealed in the photographs can be interpreted in 

 terms of specimens that can be examined at close quarters. This, how- 

 ever, is a comisel of perfection, and there is seldom time for all the 

 necessary data to be acquired. 



In reviewing the results of the photographic program to date it is 

 convenient, first, to consider the photographs in relation to the dif- 

 ferent regions and features of sea-floor topography and, second, to 

 illustrate various topics of especial interest that have emerged from 

 a study of the photographs. In some instances, color photographs 

 are used to illustrate various points, since these give a truer representa- 

 tion of the bottom. 



