72 Royal Academy of Sciences of Paris. 



singularity of form assumed by quartz rock mountains, in districts 

 remote from each other, is deduced from the peculiar construc- 

 tion and material of the mountain mass, acted upon by powerful 

 aqueous currents. Quartz rock is of great extent in the county 

 of Donegal, where in one instance it rests immediately on gra- 

 nite ; and at the murkish mountain contains a bed of pure 

 siliceous sand of considerable thickness. — The author proceeds 

 to notice the ancient beaches of Jura, which appear hitherto 

 to have escaped observation : these occur on both shoi-es of Loch 

 Tarbert, and are disposed in six or seven terraces, rising re- 

 gulai'ly from the present shore, above which the highest is ele- 

 vated about forty feet : the breadth occupied by these beaches 

 in some instances amounts to three-fourths of a mile, and their 

 line or extent has been traced eight or ten miles. — The author 

 concludes with a description and remarks on the trap dikes of 

 Jura : these are extremely numerous, and rernarkable for pre- 

 serving courses nearly parallel to each other, and nearly in the 

 line of dip of the quartz rock which they traverse ; which gives 

 occasion for offering some reasons to account for that particu- 

 lar disposition. 



ROYAL ACADEMY OF SCIENCES OF PARIS. 



March 31. — M. de la Borne exhibited some apparatus for 

 augmenting the Voltaic effects produced in the experiment of 

 M. Seebeck. They consist of a series of bars, alternately of 

 brass and of iron; ofconductorsof different sizes, one of which 

 is reduced in the middle to a very small thickness, and which 

 are to form a communication between the two ends of the pre- 

 ceding apparatus; and of one piece to form a communication 

 by very fine wires of different lengths. 



April 7. — The astronomical observations made at the Ob- 

 servatory at Paramatta by Major-General Sir Thos. Brisbane, 

 Govei-nor of New Holland, and by M. Rumker, were received. 

 — Sir T. Brisbane, in his last letter, speaks in high terms of 

 the climate of the colony, and expresses his wish that some 

 members of the Institute would visit a country which abounds 

 in objects of scientific research. He also states that he is 

 forming a collection of rarities which he intentis to present to 

 the Jardin du Roi, and that he is making preparations for the 

 measurement of an arc of the meridian. 



M. Arago communicated a letter, in which M. Duperrey, 

 now on a voyage in the corvette la Coquillcy gives an account of 

 some magnetic observations made by him at sea, and at tlie 

 isle of St. Catherine. 



M. de le Borne presented a memoir, entitled A Thermal 

 Electrometor, and formulae representing its effect. 



XV. In- 



