Dr. Hare’s Electrical Machine, §e. 279 
tive than it is positive, nor more positive than it is negative. Hence 
I do not approve of another suggestion of the same author, that the 
diminution of light near the middle of the spark results from the 
combination of the different fluids at this point. It appears to me 
that there is as little ground for supposing the union of the fluids to 
take place there as elsewhere. But admitting that the union does 
take place as supposed, is this a reason for the observed diminution of 
light? If, when isolated, either fluid is capable of emitting a brill- 
iant light, should not their co-operation increase the effect? If, 
after their union, they do not shine, it can only be in consequence 
_ of their abandoning, at that moment, all the light with which they 
were previously associated. It cannot be imagined that the light 
accompanying one should neutralize that accompanying the other. 
In deflagrating, by voltaic electricity, a wire of uniform thickness, 
equally refrigerated, = most intense evolution of heat and light is 
always midway. 
In truth, the theory which the learned author sanctions, requires 
two postulates so irreconcilable, that unless one be kept out of view, 
the other cannot be sustained. It requires that the fluids should 
exercise an intense reciprocal attraction, adequate to produce chem- 
ical affinity, and of course, enter into combination when they meet, 
and yet rush by each other with inconceivable velocity, not only 
through the air, but also through the restricted channel afforded by 
a small wire. If the fluids combine at a point intervening between 
the surfaces from which they proceed, what becomes of the com 
pound which they form? Is it credible that such a compound would . 
afford no indication of its existence? But, again, how are two sur- 
faces, the one previously deprived of a large portion of the negative 
electricity naturally due to it, the other made as deficient of the posi- 
tive fluid, to regain their natural state? By a combination midway, 
the resinous and vitreous surcharges might be disposed of, but whence 
could the vitreous and resinous deficiencies be supplied ? 
Dr. Thomson, in common with the great majority of modern chem- 
ists, ascribes chemical affinity to the attraction between the two elec- 
tricities combined with ponderable particles. As the combinations 
between such particles take place only in definite proportions, would 
it not be consistent that the fluids which give rise to them, should 
combine agreeably to those laws? But if the electrical compound, 
formed of the vitreous and resinous electricities, be decomposable by 
induction, as the theory in question requires, its constituents must be 
capable of uniting in every proportion. 
