(i3 Proceeding} of Philosophical Societies. [Dec. 



Article XI. 

 Proceedings of Philosophical Societies. 



ROYAL SOCIETY. 



The Society resumed its meetings on Thursday, the 10th of 

 November. A paper by Dr. Brewster on the Optical Properties of 

 Prince Rupert's Drops, was read. Di\ Brewster had found that the 

 glass tears known by the name of Prince Rupert's drops, and 

 formed by dropping melted glass into water, lias the property of 

 depolarizing light. On examining them farther lie found that each 

 had a number of cleavages, consisting of lines diverging from a 

 point near the bottom of the drop. He observed a second cleavage 

 parallel to the axis ; and a third, but not- so well defined, oblique 

 to the axis. In short, the glass had a triple cleavage, and was 

 crystallized. He found the specific gravity of these tears 3*261, 

 and that of annealed glass 3'27S. On slowly heating one of these 

 tears to redness, its specific gravity became 3*278, and it lost the 

 property of depolarizing light. 



On Thursday, the 17th of November, a paper by Dr. Roget was 

 read, describing an arithmetical instrument for involution and 

 evolution. The only useful arithmetical instruments at present in 

 use are the common sliding rules, by means of which multiplica- 

 tion and division are performed mechanically by means of a line 

 logarithmically divided. Dr. Roget's machine is likewise a sliding 

 rule, in which a line of logarithms is so placed as to point out the 

 different powers or roots of any number; but it would be impossible 

 to make the plan intelligible without figures. 



LINX.EAN SOCIETY. 



The Society resumed its meetings on Tuesday, the 1st of No- 

 vember. 



A paper by Mr. Sowerby was read on a fossil shell which occurs 

 in chalk, very frequently in the flint nodules. Fragments of it had 

 been observed by Cuvier and Brogniart in the chalk near Paris, and 

 from their fibrous texture they were led to consider them as frag- 

 ments of pinnae ; but from their thickness (near half an inch) they 

 concluded that the shell must have been of enormous size. Mr. 

 Sowerby got specimens of the fossil from various quarters of the 

 chalk country in the south of England. He ascertained, by com- 

 paring these specimens with each other, that it was a bivalve shell, 

 having a hinge of si peculiar structure, and constituting a genus 

 apart. To this genus he has given the name of inoccramus $ and 

 the most common species he calls inoccramus Cuvierii. 



At the same meeting, three papers by Mr. Rafancsque Smaltz 

 were read. The first was a description of a new species of fish, 

 Which he observed during one of his voyages across the Atlantic, it 



