GENERAL INTRODUCTION TO THE ZOOLOGICAL REPORTS. 



9 



as abyssal characters. The plan seemed to answer so well that we tried it again 

 a little farther south, in 1090 fathoms, and again it was perfectly successful. During 

 the remainder of the voyage we used the trawl more frequently than the dredge, 

 particularly in very deep water, where there was a certainty of finding a smooth bottom 

 free from rocks. Under these circumstances the large area covered by the trawl greatly 



Fig. 7. — The Dredging aud Sounding Arrangements on board the Challenger. 



increases the chance of bringing up some record of the scanty and sparsely-scattered 

 fauna. In very extreme depths, say between 3000 and 4000 fathoms, the trawl has the 

 disadvantage of taking rather a longer time both in letting out and heaving in, and the 

 enormous pressure of the water affects the wood of the beam. On one occasion when a 



