Magnetism, Cohesion, Adhesion and Viscosity. 521 



78° by being kept in contact for foiir-and-twenty hours with 

 the great horse-shoe magnet already spoken of, and the mag- 

 netic needle attached itself with singular readiness, contrary 

 to what had been previously found to be the case. The whole 

 effect however gradually disappeared, the attractive power 

 declining, as was ascertained by successive measurements, 

 till it fell back to its normal state of 28°, in about twentj' 

 minutes. It was by mere accident, as may be supposed, that 

 it was kept so long in contact, and most likely so long a time 

 is not necessary to produce the effect*. This result is well- 

 worthy of being contrasted with what has been said about 

 carbonate of iron, and it will be admitted, I am sure, that two 

 cases less reconcilable with analogy could scarcely be pro- 

 duced. We thus see that gelatine, and in all probability similar 

 substances, conform to the laws that have been seen to prevail 

 in vitreous bodies, and it is only necessary to observe their 

 fractured edges when hard, and particularly those of glue, 

 dried albumen and resin, to be convinced of this fact. Even 

 India rubber when in a low temperature approaches to the 

 same state, and it has been already noted that several needles 

 attached themselves firmly to it. To be convinced that this 

 view, which connects these substances with the glasses, is not 

 fanciful, it is only necessary to call to mind the case of gelati- 

 nous hydrate of silicium, which is obtained from a mineral 

 glass that dissolves in water; and it is not amongst the least 

 remarkable of the analogies that exist throughout nature, to 

 connect the liquor of jlints with broth, white of egg, gum 

 water and paste, and the last of these therefore, by a series of 

 links, with the mysterious powers of the magnet, that caused 

 St. Augustin to faint, and made Thales to believe that it was 

 animated by a soul ! 



To be quite convinced of the strong affinities that ivory, 

 mother-of-pearl, horn, albumen, tortoise-shell and quill ex- 

 hibit in common, I formed needles of these substances, and 

 tested them to an extent that left no doubt that they possess 

 the same qualities as ivory; but on the whole the quill and 

 mother-of-pearl approached nearest to a state of equality with 

 lliat substance, though there was a very slight ilifference 

 between them all. These fresh proofs leave therefore no 

 • It has since however heen ascertained that length of time was essen- 

 tially the cause of raising the magnetism of the k'"c, for on kee|)ini^ it 

 subsequently in contact for thirteen hours, its niagneiisin conkl only he 

 raised to 4f)^. Another very iin|)ort;uit point was likewise fully estahlisiied, 

 namely, that either pole of a magnet might he used without the glue 

 showing any signs of polarity, for when 7^" were ohtained it had heen kept 

 in contact with the N. end of the magnet, and when 4i)' was the amount of 

 measurement the S. end was emi)loyed, while in each case it was theS. end 

 of the needle that formed tlie connexion. 



