Royal Society of Edinburgh, 345 



tions of some new Species of Pycnoganidce. With specimens and 

 drawings." By Mr. Henry Goodsir, Surgeon, Anstruther. 



Of the genus Orithegia, one species was described, O. globosa ; 

 of Pallene one species, P. circularis ; of Nymphon four species, N. 

 pellucidum, spinosum, minutum, Knoxii ; and one species of a new 

 genus, Pephredo, — P. capillata. One of these new Crustaceans was 

 taken in Orkney, the others in the German Ocean and Firth of Forth. 

 The paper concluded with some observations on the circulation in 

 this family, and on the generative organs, the orifices of which the 

 author has detected on the under surface of the body, at the inser- 

 tion of one of the pairs of legs. «^. ^ 



Mr. Goodsir then communicated a paper by Mr. Forbes and him- | 

 self, " On a new genus of Ascidian MoUusks." This genus the 

 authors styled Pelonaia, and characterized thus : Testa cylindiical, 

 unattached ; orifices without rays, on two equal, approximated, papil- 

 lose eminences at the anterior extremity. They described two spe- 

 cies, — P. corrugata, from the Firth of Forth, and P. glabra, from 

 Rothsay Bay. The anatomy of both species was given in detail, 

 and differed from that of the attached Ascidice in its perfect bilate- 

 rality. The authors adverted to the value of the genus as a con- 

 necting link between the Molluscous and Annulose animals, and re- 

 ferred to its analogical relations to certain of the Echinodermata. 



ROYAL SOCIETY OF EDINBURGH. 



May 3rd, 1841. — Lord Greenock in the Chair. 

 The first communication was entitled " Experimental Researches on 

 the Production of Silicon from Paracyanogen." By S. Brown, M.D. 

 The author had intimated in a former paper that he had been led 

 to infer from experiment, that two familiar substances, long and uni- 

 versally regarded as distinct elements, are only modifications of one 

 and the same material form ; and having extended his inquiries, he 

 now ventures to maintain that carbon and silicon are isomeric bodies. 

 The method in which he establishes this proposition is very simple, 

 and consists in the description of a number of processes by which 

 carbon may be transformed into silicon ; and crucial experiments, in- 

 tended to prove that there is no intelligible source of fallacy in the 

 processes which are given. Accordingly, the present communication 

 is of a purely practical character. It is composed of five sections : the 

 first treats of the production of silicon from free paracyanogen ; the 

 second, of the formation of amorphous mixed siliciures of copper, iron, 

 and platinum, by the reaction of paracyanogen on these metals ; the 

 third, of the quantity of nitrogen separated from paracyanogen when 

 it is changed into nitrogen and silicon ; the fourth describes processes 

 for the preparation of definite and crystalline siliciures of iron from 

 the paracyanide of iron, and from the ferrocyanide of potassium ; and 

 the fifth gives easy formulae for the extraction of silicic acid from the 

 ferrocyanide of potassium by the action of carbonate of potassa. 



Our reason for noticing this investigation in a periodical devoted 

 to the objects of natural history, is this : If Dr. Brown's observa- 

 tions be corroborated by those who repeat his singular experiments, 



