378 REPORT — 1880. 



t'lat is to say, it gives the difference between a fixed multiple of the 

 moment of inertia and a fixed multiple of the area. In this way the 

 moment of inertia is known. The subtraction is not performed by the 

 machine, but is left to the calculator.* 



Sang's planimeter is described and figured in a paper by Mr. Sang in 

 the ' Transactions of the Royal Scottish Society of Arts ' for 1852, vol. iv. 



There is also a paper by Mr. Clerk Maxwell in the same ' Transactions ' 

 (for 185.5, vol. iv.) describing a planimeter invented by himself, and the 

 action of which depends on the mutual rolling of two equal spheres. 



These are the principal mechanical integi-ators known to the author. 

 So far as a draughtsman's purpose is concerned, Amsler's instruments 

 ajDpear to be the most convenient practically. 



The French Deep-sea Exploration in the Bay of Biscay. 

 By J. GwYN Jeffreys, LL.D., F.R.S. 



[A communication ordered by tlie General Committee to be printed iit, cxtcnso 



among the Reports.] 



I FEEL that I am indebted for the opportunity of giving an account of 

 the French expedition, which forms the subject of this paper, to my 

 esteemed friend and colleague, the Marquis de Folin, of Bayonne. He 

 was until lately the commandant of that port, and is a most zealous and 

 excellent naturalist. I may, indeed, say that the expedition originated 

 with him. For more than ten years he had, at his own expense, assi- 

 duously and carefully explored the sea-bed lying off Cape Breton, in the 

 Department of the Landes, as well as could be done in a fishing-boat ; 

 and the result of his researches among the marine Invertebrata has been 

 described, with illustrations by his pencil, in a useful work called ' Les 

 Fonds de la Mer,' published at Bayonne under his direction. M. de 

 Folin has from time to time sent me the MoUusca procured in his dredg- 

 ings for my opinion ; and our correspondence, with a visit which I paid 

 liim in December 1878, led to his making an application to the French 

 Government for the grant of a vessel to explore the depths which were 

 known to exist at a comparatively short distance from the northern coasts 

 of Spain in the Bay of Biscay. This evidently could not be done in a 

 fishing-boat ; and naturalists have much less money than science. It was, in 

 fact, a project for a nation, and not for an individual. The application was, 

 I believe, referred to the Dean of the Academy of Sciences, M. Milne- 

 J'Jdwards, whose reputation as an eminent zoologist has been universally 

 recognised for more than half a century. His report was favourable ; and 

 a Government vessel was ordered to be placed at the disposal of a Com- 

 mission of which M. Milne-Edwards was appointed President. The other 

 members of the Commission were the Marquis de Folin, Prof. Alphonse 

 Milne-Edwards, Prof. Vaillant, Prof. Marion of Marseilles, Dr. Paul 

 Fischer, and M. Perier of Bordeaux. The selection of these savants 



* A detailed description and drawings of the machine is given in the volume 

 of the Transactions of the Institution of Naval Architects for 1880. It will not 

 escape the reader that this machine requires several rather nice adjustments which 

 are not needed in the common planimeter. The machine, as actually made for sale 

 by Mr. Amsler, is very beautifully contrived, with regard to all its mechanical details, 

 and it works very smoothly and satisfactorily. Tlie cost is between £1G and £'2Q. 



