French Institute. — Collection of Shells. 393 



nOYAL ACADEMY OF SCIENCES OF PARIS. 



March 7. — The director-general of bridges and causeways 

 requested the Academy to hasten the work required of it by 

 government, on high-pressure steam-engines. — M. Ferrand 

 presented a new drawing of his marine lever. — M. de Lacepede 

 made a verbal report on M. Virey's History of the Human Race. 

 — M. Mathieu, in the name of a commission, read a report on 

 the Panorograph of M. Puissant. — M. Arago exhibited to 

 the Academy an apparatus, showing in a new form the action 

 which magnetized and non-magnetized bodies mutually exert 

 on each other. In his first experiments, M. Arago proved 

 that a plate of copper, or of any other solid or liquid substance, 

 placed under a magnetic needle, exerts on it an action which 

 immediately affects the amplitude of its oscillations, without 

 sensibly altering their duration. The phaenomenon to which 

 he now directed the attention of the Academy may be regarded 

 as the converse of the preceding. As a needle in motion is 

 stopped by a plate of copper, &c. at rest, M. Arago conceived 

 that a needle at rest would be moved by the plate when in mo- 

 tion. If a plate of copper, in fact, be made to revolve with 

 any determinate velocity beneath a magnetized needle con- 

 tained in a vessel perfectly closed, the needle will no longer 

 take its usual position : it stops without the magnetic meridian, 

 and so much the further from that plane as the rotation of the 

 plate is more rapid. If the rotary motion be sufficiently ra- 

 pid, the needle turns continually round the wire on which it is 

 suspended, whatever be its distance from the revolving disc. 



LXIII. Intelligence and Miscellanemis Articles. 



COLLECTION OF SHELLS. 



IN consequence of Mr. Swainson's going abroad, he has re- 

 quested us to make known his desire of parting with his entire 

 collection of shells, — It is not our intention to speak of the 

 scientific interest that it is known to possess, having been 

 formed by its possessor for the express purpose of writing a 

 general history of testaceous animals. It contains but tew 

 of those well known, but costly shells, which are usually seen 

 in other cabinets, neither is it rich in British Testacea; but 

 the number of species from all other parts of the work! is im- 

 mense; and in this resi)ect the collection may vie with any 

 now is this country. Their number, or even that ()t the spe- 

 cimens, has never been ascertained ; but some idea of both may 

 be formed, when it is staled that the collection occupies about 

 eight v good-sized drawers. 



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