64f Royal Irish Academy, 



ployed in the electrotype process. Several mineralogical specimens 

 were submitted to the Society. A long and highly interesting paper 

 was then read, " On the Transfer of Mineral Substances, through 

 various Fluids, by Electric Agency," by Andrew Crosse, Esq., 

 Mem. Elec. Soc. The first experiment related in this paper was as 

 follows : — Mr. Crosse kneaded some pipeclay into the consistency 

 of putty, and imbedded in it a piece of limestone and a shell ; this 

 was in a basin : he then made a mixture of powdered sand and sul- 

 phate of iron which he placed above the pipeclay, and having filled 

 the vessel with water he allowed the whole to stand for many months. 

 This arrangement was made in imitation of a natural arrangement 

 of like character which had fallen under his notice, and in which the 

 shells and carbonate of lime had become coated with sulphate of 

 lime. In hopes of attaining the same result artificially, this experi- 

 ment was instituted ; and to the great satisfaction of the author 

 when he examined the results, the shell and the limestone had lost 

 in weight, and around each were crystals of sulphate of lime. It is 

 Mr. Crosse's strong conviction, that though many mineral produc- 

 tions may result from the direct action of electric currents, yet far 

 the largest portion proceed from operations analogous to this, — 

 from the direct electrical affinity or attraction between particles of 

 matter coming into contact by this slow and constant action. The 

 only point in which this experiment differed from nature is, that 

 the vessel in which the operation was carried on was not porous. On 

 this point Mr. Crosse stated a fact which will not be forgotten by 

 electrotypists, that voltaic deposits are more abundant when the 

 vessel employed is porous, so that the sulphate of copper can slowly 

 filter through. A series of experiments, some completed, others in 

 progress, were then described, in one of which the mould of a sove- 

 reign was produced in solid marble, by an action not dissimilar in 

 principle to that just described ; and in a modification of the ar- 

 rangement a rod of glass, connected with the positive end of the 

 battery, was gilded. The author does not doubt the possibility of 

 forming any minerals, even the precious gems, by electric agency. 

 He thinks the pearl to be nothing more than alternate layers of 

 animal and mineral substances, electrically concreted. In one of 

 the experiments a magnificent group of fine Acari were developed : 

 the production of these insects is still an object of attention to Mr. 

 Crosse, and he anticipates ere long communicating with the Society 

 on the subject. 



Mr. Weekes's Register was then read : and the Chairman stated 

 that Mr. Walker's second paper on Lightning Conductors would be 

 read at the next meeting. 



ROYAL IRISH ACADEMY. 

 [Continued from vol. xx. p. 600.] 



May 10, 1841. — A Note on some new Properties of Surfaces of 

 the second Order, by John H. Jellett, Esq., F.T.C.D., was read. 



I. Let the points on the focal conic, at which the tangent is par- 

 allel to the trace of the tangent plane, be considered analogous to foci. 



