l86 CHALLENGER 



were restricted within the Baltic ; however, soon after the War 

 was over they were ready to take the field of world-wide oceano- 

 graphic exploration, and, under the enthusiastic guidance and 

 leadership of Professor Hans Pettersen, the now famous Albatross 

 expedition set out. 



This expedition was following many lines of investigation, in- 

 cluding continual echo sounding of the ocean areas to be crossed, 

 but perhaps the most interesting part of the work to the layman 

 was the proposal to obtain cores, or long vertical samples, of 

 the sediments lying on the ocean bed. This was successfully 

 achieved by using the Kullenberg piston corer. The device is 

 lowered on a wire hawser from a winch to the sea-bed, and if the 

 ship is properly handled, a small pilot weight reaching the sea-bed 

 first releases a larger weight which drives the coring tube into 

 the sediment. A piston within the coring tube is attached directly 

 to the wire from the winch, which has been braked as the bottom 

 is reached. The piston thus remains still while the tube goes into 

 the sediment. The partial vacuum so formed assists the sediment 

 to enter the tube. The resulting core samples of the ocean floor 

 sediments can be seen in plastic containers giving a cross section 

 view, the sediments seen at the lower end of the tube having 

 been laid down hundreds of thousands of years before. The dif- 

 fering colours of the predominant sediments, whether it be fine 

 wind-blown sand or the calcerous skeletons of countless plankton 

 forms, when viewed as it were in cross section give the im- 

 pression of looking at a layered cake having an infinite variety of 

 cream fillings. 



The Challenger cruise being planned in 1949 aimed at taking 

 a very considerable number of soundings in the oceans, as well 

 as carrying out searches for a number of shoals reported in such 

 areas, particularly in the latter years of the War when thousands 

 of ships were running their echo sounding machines — many of the 

 operators interpreting their sounders correctly while others 

 'discovered' shoals which never existed. 



At the same time it was arranged to take a small party of 

 scientists from the Department of Geodesy and Geophysics, Cam- 

 bridge, to explore the structure of the ocean bed itself. This was 

 to be done by using seismic refraction methods already in use 

 on land but now adapted for use from a ship with over 2600 



