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substance is exposed to the sun’s rays, are not due, as has long been sup- 
posed, to the agency of light, but are simply and purely a result of unequal 
heat, the crystals always forming upon the coldest side of the bottle. He 
has done the cause of science a service by correcting statements upon the 
subject which have been made in nearly all our leading chemical works. 
Principal J. D. Forbes has published an elaborate paper in the “Trans- 
actions of the Royal Society of Edinburgh,” “On the Conduction of Heat in 
Bars, and the Conducting Power of Wrouglit-Iron,” and has observed that 
the order of arrangement of the “ conductors of heat differs but little from 
their order of conduction for electricity,” and thus confirms the results 
previously obtained by Wiedmann and Franz ; also that “the diminished 
conducting power of iron, by increased temperature, harmonizes with 
similar facts in electricity.” 
M. Reitlanger has communicated a memoir to the Academy of Sciences 
at Vienna, “On the Sounds and Motion which take place within the 
Voltaic Arc.” He employed Trevelyan’s apparatus, driven by a voltaic 
current according to Mr. Page’s process ; and in some of the experiments 
the apparatus was placed in an exhausted receiver. He concludes that the 
sounds emitted by the above apparatus, as well as the motion of the re- 
volving globes of Mr. Gore, are simply mechanical results of the electric 
discharge between the various movable metallic parts of the apparatus, 
where they are in imperfect contact with each other, and result especially 
from the tearing action. 
Some interesting details respecting a discharge of lightning down a 
poplar tree are given in L'lnstitut. The lightning produced a groove 
like the furrow of a ploughshare, which did not proceed in a vertical line, 
but followed a spiral direction down the tree. It is interesting to notice 
this direction of action, as in another instance, at Birmingham, on the 
occasion of the Queen’s visit to that place, lightning struck a pole fixed 
upon the Town Hall, and the direction taken by the electricity was also 
in that case in the form of a spiral down the pole. 
