CH. l] THE EXPLORATION OF THE SEA 3 



biological enquiry, so far as it is not a mere catalogue of the 

 names, characteristics, and distribution of organisms, is to be based 

 on the results of physical investigation. 



The sounding machines. The names of these are legion. 

 But when the industrious reader wades through the descriptions 

 of those of Brooke, Baillie, Belknap, le Blanc, Massey, Sigsbee, 

 Tanner and Thomson (to take only a selection in alphabetical 

 order) he will find it convenient to consider only the latest — the 

 Lucas automatic sounding machine — for this possesses merits 

 which render it unnecessary (at least for our present purpose) 

 to consider the others. In it are the characteristics of the best 

 type of English machinery — elegance, simplicity, compactness and 

 efficiency. Its evolution is the result of commercial enterprise. 

 So long as a knowledge of the depths of the sea was a purely 

 scientific study the ability and expense expended on effort to 

 obtain it were restricted within obvious limits. But when the 

 acquisition of this kind of knowledge became an " economic 

 problem " invention galloped. When it became necessary to 

 obtain an exact knowledge of the contour of the bed of the sea 

 for the purpose of laying telegraph cables, the modern sounding 

 machine came into existence. When further it became a matter 

 of some considerable expense to stop an ocean liner on her voyage 

 in order to obtain a sounding, the "depth-indicator" was soon 

 evolved \ 



A "deep-sea" sounding may be regarded as one taken in 

 water of over 200 metres in depth. To make this rapidly and 

 exactly, and at the same time to obtain a sample of the deposits 

 on the sea floor, is essential. Of necessity a very long sounding- 

 line is required, and this must be carried down to the bottom 

 very quickly so that the line remains vertical. To do this a 

 heavy sounding lead is attached to the end of the line, and 

 obviously the latter must be strong enough to carry the weight. 

 Yet the line must not be too heavy for it would otherwise possess 

 in itself a very considerable mass. Now a thin line may be em- 

 ployed which will carry the lead when the latter is descending, 



1 In the depth-indicator a glass tube, open at one end, is lowered to the bottom. 

 Water rises into the tube compressing the air. The depth is estimated by the 

 application of Boyle's Law. 



1—2 



