^S* Boyal Society. — Linticean Society. 



fore described ; viz. the percliromate of iron, dichromate of lead 

 and silver, double chromate of potash and soda, and double chro- 

 mate of potash and magnesia. The author concludes this paper 

 with an account of his analysis of the mineral known in cabinets as 

 chromite of iron, which, when examired in a state of purity, he 

 found to consist of 2 atoms of green oxide of chrome, 1 of per- 

 oxide of iron, and 1 of alumina, together with an admixture of a 

 white matter, apparently a metallic salt, of unknown acid and base, 

 but too minute in quantity for thorough examination. 



The Society then adjourned to 



April 26, when Dr. J. Blackman was admitted a Fellow, and 

 H. R. H. the Duke of Clarence elected a Fellow, of the Society. 



A paper was read, entitled, " On the derangement of certain 

 transit instruments by the effects of temperature ; by Robert Wood- 

 house, Esq. F.R.S. Plumian Professor of Astronomy in the Univer- 

 sity of Cambridge." 



In the Philosophical Transactions for 1825, the author alluded 

 to the derangement of the Cambridge Transit Instrument, arising 

 from unequal expansion of its braces, establishing as he con- 

 ceived the fact and cause of such derangement ; and in a subse- 

 quent paper instanced its effects in one case as altering by no less 

 than 20' the time of the passage of the pole-star over the wires. 

 The removal of the braces was in consequence resolved on ; but 

 from one cause or other, delayed ; though the Author considers 

 good to have arisen from this procrastination, as enabling him to 

 make further experiments, which he was led to do, in consequence of 

 Mr. South's observations, which led to conclusions opposite to those 

 deduced by himself. To satisfy his own mind, therefore, he insti- 

 tuted the series of experiments described in this paper, from which 

 he concludes that the partial heating of the diagonal braces, or of 

 any one of them, deranges the Cambridge Transit Instrument ac- 

 cording to the reasoning in his former paper ; and that this cause 

 may, in certain instruments, and under certain circumstances of 

 temperature, produce balancing-effects, thus giving an appearance 

 of inflexibility, which under other circumstances would not subsist. 



LINNiEAN SOCIETY. 



]yray 1. — A large collection of New Holland Birds and Quadru- 

 peds, presented by Sir John Jamieson, were upon the table. 



The Society proceeded to fill up the vacancies in the list of 

 Foreign members, when the following gentlemen were elected : — 

 Henry Ducrotay de Blainville; Charles Lucien Bonaparte, Prince 

 of Musignano ; Leopold von Buch ; Viscount Henry de Cassini; 

 Henry Fred. Link, M.D. ; C. F. P. von Martius, M.D.; C. G. Nees 

 von Esenbeck, M.D.; Ch. Asmund Rudolphi, M.D. ; Auguste de 

 Saint-Hilaire ; Frederick Teidemann, MD. 



A description was read of a new Genus belonging to the natural 

 family of plants called Numphaacece ; by Nathaniel Wallich, M.D. 

 F L.S. superintendant of the Botanic Garden, Calcutta. The fol- 

 lowing is the character of the genus : 



Hydrostemma : (Polyandria Polygynia.) — Sepala 5 distincta, 



infra 



