Chemistry and Physi 
they are given by observations at St. Petersburgh, Greenwich, Hobar- 
ton, Toronto, Cape of Good Hope, St. Helena and §j 
this, he endeavors to explain the night action, the 
the contrary course of the needle for the same hours 
cal time dependent on-the distribytion of land an 
slative —_ of eceding months, ahd the tinual 
ecially in the tropical regions, of the higheryemperature of 
the northern megan, above that of the south. these points 
the author sees such an agree vende between tho natural re 
which are suggested by the. assumed physical cause of 
variations, as to give him a growing confidence in the 
views he has put forth. 
Jaguerrotypes by Galvanic Light; by B. Situmma 
1840, in company wi ith Dr. W. H. Goone, I showed the pos: 
taking j impressions on an iodized silver plate by the light of a‘ ower- 
ful voltaic pile. An ount of our trials on that occasion wa Pay 
lished in this Journal, first series, vol. xliii, 
Since that time my attention has not bedi: ealled to the niegh bal 
lately, when the arrival at the Louisville Laboratory of o 
boscq’s regulators of the pa light by an electro-magnet, ‘sugheged 
the propriety of repeating the expen: The battery employe 4 in 
i aan series of 900 pairs of zinc and copper all 
i: plunged ne moveme d which ‘upc is still (as then) a 
i bsence at that time ef any contrivance like that of Duboseg for its reg: 
ulation. 
The battery employed in the present trials was composed of fifty 
; pairs of Bunsen’s carbon battery made by Deleuil of Paris, Although 
very powerful, it could not be at all ridin with the 900 members of 
the old arrangement in its initial effect, this defect is more than 
compensated in its constancy. Our first trial was to make a copy of 
and the experiment was con niinued throug a two minutes. e 
result showed =i co relative distances of ‘the light, the figare, and the 
instrument were not properly adjusted. An impression was pr roduced 
but it was faint and pai cg a longer exposure than usual to the vapor 
_ of mercury to develop 
It was afterwards +e better to bring the figure within about twelve 
feet of the light and also to approac the camera somewhat nearer. 
With mompeiceion excellent impressions were procured in forty sec- 
> onds—and it was the conviction of Mr. Stancliffe, the excellent daguer- 
bone in aria and who kindly aided me in these experiments, — 
