372 Miscellaneous Intelligence. 
effects of a pile ofa single metal, terminating at one side in a point, 
and the other in a large surface, and placed end to end in water, with 
merely this geometrical difference, proves evidently that something of 
this kind exists, and it was whilst occupied with these piles on geo- 
metrical principles that the author was conducted to researches on 
incandescent points. 
If the rays of the sun, by heating the soil, produce an effect ana- 
logous to that spoken of, 2. €., to increase the electric repulsion, but 
only in the proportion required to make the positive fluid overcome 
the resistance of the air, and not the negative, it would explain the 
habitually positive state of the lower strata of the atmosphere. The 
author has not, however, found this idea confirmed by experiments 
with the aphlogistic lamp. In fact, when left on a condenser for 
several hours it had not disturbed the electrical equilibrium, 2, e., the 
excess of expansibility acquired by the positive electricity was not 
sufficient to detach it from its combination with the negative electricity. 
2. On the Magnetic Action of strong electrical Currents on different 
Bodies.—Coulomb, in 1802, gave the results of a well-known series of 
experiments on the action exerted by the opposite poles of two power- 
ful magnets on minute needles of any substance delicately suspended 
between them. It was found that, whatever the nature of the sub- 
stance, the needle ultimately arranged itself in the direction of the 
poles; but he finally concluded that this was due to the minute 
portions of iron which they contained. 
M. Biot, who repeated these experiments very carefully, is not 
entirely of this opinion; but suggests, that inasmuch as simple con- — 
tact of heterogeneous bodies is sufficient to develop electrical forces, 
which for a long time were quite unsuspected, perhaps other cir- 
cumstances may develop similar or analogous forces extremely 
feeble, but sufficient to affect apparatus delicate as Coulomb’s. 
After this M. Ampere, with M. A. Delarive, made an experiment 
at Geneva on the effect of electrical currents on a plate of copper, 
and conceived that the copperplate, by being near the currents, was 
capable of affecting the magnet like the neighbouring wires, through 
which the current was passing, but afterwards ascertained that this 
was not the case. 
Ultimately M. Becquerel has resumed the examination of these 
or similar phenomena, making use of Schweigger’s multiplier for 
the concentration of the powers of the clectrical current, and he 
has observed differences between the effects thus produced and those 
obtained in M. Coulomb’s experiments. The galvanometer used was 
1.97 inches long and about 0.4 inches wide. Care was taken that the 
substances should not be worked with iron instruments, and the needles 
formed of them were made very small, especially if of a substance 
but feebly affected by the electrical current; they were then suspended 
