C 77 1 

 XVII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



June 27. jL he President in the chair. Professor Playfair 

 furnished a lithological survey of Shehalean, one of the 

 Grampian mountains in the north of Scoiiand, on which 

 the late Dr. Maskelyne made his ingenious experiments to 

 ascertain the attraction of the mountain on a plummet, and 

 also the mean density of the earth. Part of this paper con- 

 sisted of mathematical tahlcs of a nature not to be read. 

 The professor discovered with some difficulty the parts 

 where Dr. M. had taken his angles from, and then pro- 

 ceeded to examine the rocks which compose the mountain: 

 these he found to be chiefly granular quartz and micaceous 

 schist, with their varieties. Mr. P., after taking a general 

 survey of the position, bearings, surface, elevation and per- 

 pendicular sides of tne mountain, collected specimens of 

 the different rocks which compose it, and ascertftuied their 

 specific gravity with great care and minuteness. 



July 4. — A paper bv Dr. Wells was read on vision. The 

 purport of the author's observations was, that the focal di- 

 stance of the eye depends chiefly on the contractibility of 

 its muscles, and that the latter is much greater in youth 

 than in persons of njore advanced years. In youth the eye 

 is capable of acconniioaating i'self to the light and the 

 distance of external cbjects, but in old age this contractile 

 power of the muscles ctases, arid the focal distance of the 

 eve becomes shorter, and more fixed to a determinate point. 

 Dr. Wells has made some experiments both when young 

 and old, and caused others to make sirni!ar ones, with bella 

 donna applied i ) the eyes : thi^ plant increased the action 

 of the ocular muscles in the yount^. but not in tne o\d sub- 

 ject. Hence he mierred t'.iat short sight is less owing to 

 the prominence or figure of the pupil, than to the flexibility 

 of the muscles which dnect it. 



The Society then adiuurncd, during the long vacation, till 

 Thdrsday the lOth of November next. 



XVIII. Intelligence and Miscellaneous jliticles. 



J. HE eleventh Number of Lcvhonrn's' Mathematical Re- 

 pository coniauis, 1. S )lutionr. to ilif; nialh;.MT)aiii.al ques- 

 tions propo'icd in Number IX; 2. Solutions to ;! curious 

 problem in dynamics 3 3. Expansion of a formula con- 

 nected 



