Notices respecting New Books. 61 
eannot deviate from the beaten track of his predecessors without 
the aid of new combinations; and when the supply of these is 
derived from his own industry and ingenuity, the ardour of his 
pursuit will be unimpeded by the delays or mistakes of others ; 
and the projection of any required improvement may conse- 
quently be followed by its immediate consummation.” 
In describing the mechanical effects of electricity, Mr. Singer 
has particularly enlarged on the expansive effects it invariably 
produces when passing from one conductor to another, and has 
very successfully applied the observation of this effect to explain 
the results obtained by Mr. Symmer, when a charge is passed 
through several sheets of tin-foil placed between the leaves of 
a paper book, which were considered as an indication of the 
course of the electric fluid. As Mr. Singer has published a 
separate paper on this subject in The Philosophical Magazine, 
it is unnecessary for us to enter more fully on the subject. The 
following experiments will probably be new to many of our 
readers. ‘* Colour both sides of a card with vermilion, and place 
it upon the table of the universal discharger; one of the wires 
should be beneath the card, and the other in contact with its 
upper side; the distance of the points of the wires being one 
inch. Ifa charge be now passed through the wires, the fluid 
will pass from the positive wire across the surface of the card to 
the part over the negative wire, and it will perforate the card 
in its passage to the negative wire. The course of the fluid is 
permanently indicated by a neat black line on the card, reaching 
from the point of the positive wire to the hole; and by a dif- 
fused black mark on the opposite side of the card around the 
perforation, and next the negative wire. These effects are very 
constant, the black line always appearing on the side of the 
card which is in contact with the positive wire, and the perfora- 
tion being near the negative wire.” 
Mr. Singer has also found that a light float-wheel, made of 
eard paper, and placed between two oppositely electrified points, 
will move from the positive to the negative; and that a piece of 
card paper supported vertically by a narrow cork base in a si- 
milar situation, is thrown down also from the positive towards 
the negative. ' 
The experiments appear to us amongst the most satisfactory 
that have been offered in evidence of a current of electricity 
from the positive to the negative surface, but we do not regard 
them as absolutely decisive. 
. The chemical agencies of electricity include ouly the effects 
of common electricity, the action of the Voltaic apparatus being 
reserved for the concluding part of the work. ‘The action of 
the electric charge on metals is treated at some length, and the 
description 
