Royal Society. 14S 



them, with regard to the law in question, is, that the intensity varies 

 nearly as the square of the diameter : but several causes contribute 

 to interfere with the accuracy of this determination, and to exhibit 

 the power as a mean of 1*844 instead of 2 j the principal of which is 

 the action of the coils upon each other. 



By other methods, in which two wires of different lengths and dia- 

 meters are placed so as to oppose each other in their effects, the ac- 

 curacy of the conclusion that this power is the square, was satisfac- 

 torily established. Hence he arrives at the general conclusion, that 

 the intensity or conducting power varies as the mass or weight di- 

 rectly, and as the square of the length inversely. 



A paper was then read, entitled, " Note on the Tides." By John 

 William Lubbock, Esq. V.P. and Treasurer of the Royal Society. 



This communication contains some interesting results which Mr. 

 Lubbock has obtained from observations made at Plymouth, Ports- 

 mouth, and Sheerness, under the superintendence of the Masters at- 

 tendant at those dockyards. Mr. Dessiou has,- with extraordinary 

 perseverance, just completed the discussion of about 6000 additional 

 observations of the tides at the London Docks, with a view to found 

 on a more certain basis the corrections of the moon's parallax and 

 declination. The results which he has obtained are utterly irrecon- 

 cilable with the theory of Bernoulli, and therefore the tables com- 

 puted upon that theory must be rejected as inaccurate. 



A paper was also read, entitled, " On the Nature of Sleep." By 

 A. P. W. Philip, M.D. F.R.S.L.&E. 



The author intends the present paper as a continuation of his in- 

 quiries into the relations subsisting between the nervous and muscu- 

 lar systems, which form the subject of his former papers, but which 

 would be incomplete without the consideration of their condition 

 during sleep. With this view he proposes to determine the particular 

 organs, on the condition of which this peculiar state of the system 

 depends ; the laws by which it is governed ; and the influence it has 

 upon other parts of the system. The necessity of intervals of repose 

 applies only to those functions which are the medium of intercourse 

 with the external world, and which are not directly concerned in the 

 maintenance of life. The organs subservient to these two classes of 

 functions may be viewed as in a great degree distinct from one an- 

 other. The brain and spinal marrow constitute alone the active por- 

 tions of the nervous system. The law of excitement, which regulates 

 the parts connected with the sensorial functions, including sensation, 

 volition, and other intellectual operations, and the actions of the vo- 

 luntary muscles, is uniform excitement, followed by a proportional 

 exhaustion ; which, when occurring in such a degree as to suspend 

 their usual functions, constitutes sleep ; all degrees of exhaustion 

 which do not extend beyond the parts connected with the sensorial 

 functions being consistent with health. On the other hand, the law 

 of excitement of those parts of the brain and spinal marrow which are 

 associated with the vital nerves, and are subservient to the vital func- 

 tions, is also uniform excitement -, but it is only when this excitement 

 is excessive that it is followed by any exhaustion ; and no degree of 



