Rote ae 
Chemistry. 427 
sound to a vibration in the interior of the iron bar, or a new arrange- 
ment of the molecules; but they are not agreed on the mode of vibra- 
tion; de la Rive believing it to be transversal, and Matteucci endeavor- 
ing to prove it to be longitudinal. M. Wertheim, after a series of ex- 
periments, has ascertained that there are at times, both longitudinal and 
transverse vibrations. His experiments were made with a bar of iron 
two meters long and one centimeter thick, which was fixed at middle in 
a horizontal position, and had each half enclosed in a large glass tube, 
which tubes were wound with a spiral of copper wire. A coil of copper 
wire (1336 metres in length, and 19 centimeters in its inner diameter) 
was afterwards substituted for the two helices, and placed with its axis 
coincident with the axis of the bar. On completing the circuit, the lon- 
gitudinal sound, although feeble, could be distinguished, and the bar 
was a little lengthened in the direction of the axis. When the axis of 
the coil was one side of the centre, the bar was attracted and bent to- 
ward it, and resumed its first position only on the:cessation of the cur- 
rent. ‘Thus by varying the position of the coil, the bar could be bent 
horizontally or vertically, or in an intermediate position, and the flexure 
amounted to several millemeters. In opposition to the deduction of 
Guillemin, from his experiments, M, Wertheim has shown that the elas- 
ticity 6f iron is diminished by magnetization. He is preparing to ascer- 
tain by direct micrometrical investigation, the amount of elongation 
which the iron bar is believed by him to undergo. 
M. Guillemin, in the experiments alluded to, found that a bar of iron 
wound with a spiral of copper wire, supported at one end and bent by 
a weight suspended from the other, sensibly straightened itself, on the 
passage of a magnetic current through the copper wire. 
4, Electric excitement of paper ; by Rev. H. G.O. Dwicxt, (commu- 
nicated. )—It is well known that friction will excite electricity in a sheet 
of paper, especially if it be thoroughly dry. This is well shown by 
placing the paper on a warm stone, for a moment, when a single pass- 
ing of the palm of the hand will produce electric excitement. On rais+ 
ing the paper carefully from the stone, sparks may be obtained from 
different parts of it by the knuckle. If a piece of tin plate be placed on 
the paper arranged on the stone, and pressed down, on raising the 
whole carefully, a strong spark is procured; and if it be returned to 
the stone, and the plate again pressed strongly upon the paper, another 
spark is given out on again raising it. 
If the sheet of paper with the tin plate mentioned above, be charged 
as just explained, and then be removed carefully, and placed on a sheet 
of tinfoil upon the top of an insulated stool,and pressed down with a 
cer at the centre,—on raising it, a strong spark will be obtained from 
the tinfoil, and another from the lower surface of the tin plate through 
the paper. This simple electrical machine may be again charged by 
