CONTENTS. IX 



Page 



XXIX. On the Refractive Power of the Two New Fluids in 

 Minerals, with Additional Observations on the 

 Nature and Properties of these Substances. By 

 DAVID BREWSTER, LL.D. F. R. S. Lend., Sec. 

 Ri 8^ Edin.;, and Corresponding Member of the 

 Academy of Sciences of Paris, - 407 



XXX. Observations on Two Species of Pholas, found on 



the Sea coast in the neighbourhood of Edinburgh, 

 By JOHN STARK, Esq. M. W. S. Communica- 

 ted by Dr BREWSTER, - 433 



XXXI. Description of a new Register Thermometer, with- 



out any Index > the principle being applicable to 

 the most delicate Mercurial Thermometers. By 

 H. H. BLACKADDER, Esq. F. R. S. E. , 440 



XXXII. On a new Photometer, founded on the Principles 

 of Bouguer. By WILLIAM RITCHIE, A. M. 

 Rector of Tain Academy. Communicated by 

 Dr BREWSTER, - 443 



HISTORY OF THE SOCIETY, - 447 



Laws of the Society, enacted 23d May 1811, and altered 

 6n the 26th February 1820, 24th January 1823, 13th 

 January 1824, and 9th January 1826, _ 449 



List of the Office-Bearers and Members elected since 

 March 3. 1823, - _ _ 457 



List of the present Ordinary Members of the Society in 

 the order of their election, - r> _ 



