290 Analyses of Books. [Ocr. 
seemed to prove an internal connexion between magnetism and 
electricity, and he relates some fruitless experiments which had 
been instituted for the purpose of discovering whether magne- 
tism, electricity, and galvanism, might not be identical. Prof. 
Cumming afterwards relates the various experiments which he had 
made on the subject of electro-magnetism, and describes the 
nature of the apparatus employed, and having determined the 
difference between galvanic magnetism and electricity, as to the 
power of being conducted, he was desirous of discovering whe- 
ther there was any thing analogous in common magnetism. 
With this view he relates the following experiment: “ r placed 
beneath the iron pendulum ofasmall clock a horse-shoe magnet, 
whose force coinciding with that of gravity, would accelerate 
the rate of the clock, by the going of which a measure would be 
afforded of the magnetic force exerted uponit. When the poles 
of the magnet were uncovered, the rate of the clock was accele- 
rated from 10’ to 12’ in 24 hours ; when they were connected by 
a piece of soft iron, the gain was not more than from 1’to 2’; on 
filing away the middle of the iron, the rate was gradually accele- 
rated, and when the central part was reduced to fine thread, the 
acceleration was nearly the same as when the poles were unco- 
vered. When the poles were connected by a piece of iron bent 
down beneath the legs of the magnet, so that the length of the 
circuit between the poles was considerably increased, the rate of 
the clock was but little affected. It appears from this,” says 
the Professor, ‘ that the poles of the magnet were much more 
completely neutralized when the connexion between them was 
made through the longer but more capacious circuit, than when 
through the shorter and less capacious; and that in this respect 
common magnetism is analogous to that excited by the galvanic 
apparatus.” 
The author concludes this paper by observing, that there are, 
perhaps, few instances in the history of science, of nearer approx 
imations to discovery than some of those connected with this 
subject. In the seventh volume of Nicholson’s Journal, an 
account is given of an experiment for ascertaining the effects of 
galvanism upon a magnetic needle; which failed, as we now 
know, because the compass was placed fortuitously upon the 
pile, instead of being under or over the wires connecting its 
extremities. 
When it was attempted to magnetize steel bars, by placing 
them in the circuit of the large electrical machine at Harlaem, it 
was observed that they became most strongly magnetic when the 
discharge was passed through them transversely. . 
VIII. On the Application of Magnetism as a Measure of Elec- 
tricity. By the Rev. J. Cumming, MA. FRS. &c. &e. 
Prof. Cumming observes, that the methods hitherto in use for 
ascertaining the quantity and intensity of the electricity produced 
either by friction or by galvanic action, are derived from its power 
