Intellisrence and Miscellanies. 215 



-to 



The author designs to pubUsh a more circumstantial ac- 

 count of his observations. — Annates de Chimie et de Physi- 

 que, Aout, 1828. 



25. Autumnal coloration of Leaves. — A memoir on this 

 subject, by M. Macaise-Princep, read before the Societe de 

 Physique et D'histoire naturelle de Geneve, concludes as fol- 

 lows : 



1. All the colored parts of vegetables appear to contain 

 a particular substance, (which the author, in conjunction 

 with Prof. DeCandolle, agrees to call Chroinule,) suscepti- 

 ble of a change of color by slight modifications. 



2. It is to the fixation of oxygen, and to a sort of acidifi- 

 cation of the chromule, that we are to ascribe the autumnal 

 change in the color of leaves. — Idem. 



26. Singular Galvanic trough. — M. Watkins, philosophi- 

 cal instrument maker of London, has constructed a Voltaic 

 pile, with a single metal and without any liquid. It consists 

 of from 60 to 80 plates of zinc, four inches square, fixed in a 

 wooden trough at a short distance from each other, having 

 only a thin plate of air between them. One side of each 

 plate is smoothed and polished, the other left rough. The 

 polished faces are all turned in one direction. If one ex- 

 tremity of the pile be made to communicate with the ground, 

 and the other with an electroscope, the latter immediately 

 indicates one or other of the two electricities, according to 

 the pole with which it is in contact. The humidity of the air 

 favors the action of the pile, which may be considered as a 

 kind of dry pile in which air is substituted for paper, and the 

 two surfaces of the zinc do the office of two heterogeneous 

 metals. It appears to be owing to the stronger oxidation 

 of the polished surface that we are to ascribe the develop- 

 ment of electricity in each plate of the zinc ; the intermedi- 

 ate strata of air, and perhaps the trough permitting this elec- 

 tricity to accumulate as in the ordinary pile. — Idem. 



27. On a method of measuring some varieties of Chemical 

 action, by M. Babinet. — In producing the disengagement of 

 a gas in close vessels, the chemical action ceases when the 

 gas acquires a sufficient elastic force ; and this action is sus- 

 pended until the compressed gas is liberated, the force of 



