84 Biographical Sketch of [August, 



to the excess or defect of a single fluid. Every one must admit 

 that he defends his hypothesis with much ability, and even with 

 the precision of mathematical reasoning ; but we must recollect 

 that the whole is founded upon a gratuitous assumption, and that 

 we are not entitled to employ the agency of two fluids in our 

 explanations, until we have found it impossible to explain the 

 phenomena by the supposition of a single fluid. If, therefore, 

 the theories are equally plausible, we shall be obliged to reject 

 the one which proceeds upon the assumption of the greater 

 number of hypothetical principles. 



In the science of magnetism, upon which Coidomb bestowed 

 a great share of attention, we may observe the same tendency 

 to assume imaginary data, upon which, however, he reasons with 

 much precision, and from which he derives a beautiful and 

 consistent theory. In order to explain the action of the magnet, 

 he supposes that all the particles of the instrument are so many 

 partial magnets, having their opposite poles in contact. The 

 operation of these poles will, in a great measure, be neutralized 

 by each other, so that the two extreme poles only will be in a 

 state' of activity. This hypothesis, like the one on electricity, 

 he defended with much ingenuity, and he showed that it was 

 adequate to explain all the phenomena, but, like the former, it 

 rests upon a gratuitous foundation. Besides his hypotheses, he, 

 however, made some important observations on magnetism, espe- 

 cially those that refer to the effects produced upon it by temper- 

 ature. He found that the magnetic property of the needle is 

 diminished as its temperature is increased, and that probably, at 

 a certain high temperature, it would be entirely destroyed ; this 

 degree was too high to be ascertained by direct experiment ; but 

 by employing a theorem of Laplace, it was estimated at the 

 700° on the centigrade scale, or about 1,450° of Fahrenheit. By 

 means of the delicate sensibility of his torsion balance, Coulomb 

 conceived that he was able to detect the magnetic property in 

 many bodies which were not suspected to contain iron, and was 

 finally induced to form the conjecture, that magnetism, like 

 electricity, may exist in all bodies, though it is frequently con- 

 tained in them in a latent state, and requires a particular com- 

 bination of circumstances for its development. This idea 

 appears, however, to have been brought forwards rather as a 

 speculation, which might be confirmed or refuted by future expe- 

 riments, than as forming a part of his matured theory, and is 

 contrary to the opinions that are generally entertained upon the 

 subject. The experiments and researches of Coulomb on 

 electricity and magnetism were more directed to the establish- 

 ment or elucidation of his hypotheses than to the development 

 of any new facts ; so that, although he devoted so much of his 

 attention to these departments, he has produced in either of 

 them very little of what can properly be considered as disco- 

 veries. So far as our information extends, the torsion balance of 



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