CHEMICAL SCIENCE. 277 



that, on the contrary, the phenomenon in relation to change of density 

 (when near the point of solidification) is shared with every substance with 

 which we are at all familiar in a molten state, so entirely so, that Mr. Nas- 

 myth felt himself wairanted in propounding, as a general law, the one 

 hcfore stated, namely, that in every instance in which he has tested its 

 existence he finds that a molten substance is more dense, or specifically 

 heavier, than the same substance in its unmoltcn state. It is on account of 

 this that if we throw a piece of solid lead into a pot of melted lead, the solid, 

 or unmolten metal, will float in the fluid, or molten metal. Mr. Nasmyth 

 stated, that he found that this fact of the floating of the unmolten substance 

 in the molten holds true with every substance on which he has tested the ex- 

 istence of the phenomenon in question. As, for instance, in the case of lead, 

 silver, copper, iron, zinc, tin, antimony, bismuth, glass, pitch, rosin, wax, 

 tallow, c. ; and that the same is the case with respect to alloys of metals 

 and mixtures of any of the above-named substances. Also, that the normal 

 condition as to density is resumed in most substances a little on the molten 

 side of solidification, and in a few cases the resumption of the normal con- 

 dition occurs during the act of solidification. He also stated that, from 

 experiments which he had made, he had reason to believe that by heating 

 molten metals up to a temperature far beyond their melting point, the point 

 of maximum density was, as in the case of water at 40 deg. about to be 

 passed ; and that at such very elevated temperatures the normal state, as 

 regards reduction of density by increase of temperature, was also resumed, 

 but that as yet he has not been able to test this point with such certainty as 

 to warrant him to allude further to its existence. Mr. Nasmyth concluded 

 his observations by stating, that he considered this to be a subject well 

 worthy of the attention of geologists, who might find in it a key to the expla- 

 nation of many eruptive or upheaving phenomena which the earth's crust, and 

 especially that of the moon, present, namely, that on the point of solidifi- 

 cation molten mineral substances then beneath the solid crust of the earth 

 must, in accordance with the above-stated law, expand, and tend to elevate 

 or burst up the solid crust, and also express upwards, through the so 

 cracked surface, streams more or less fluid of those mineral substances which 

 we know must have been originally in a molten condition. Mr. Nasmyth 

 stated, that the aspect of the lunar surface, as revealed to us by powerful tel- 

 escopes, appeared to him to yield most striking confirmation of the above 

 remark. He concluded by expressing a hope, that the facts which he had 

 brought forward might receive the careful attention of scientific men, which 

 their important bearing on the phenomena in question appeared to him to 

 entitle them to. 



A gentleman in the section asked Mr. Nasmyth whether the facts well 

 known to chemists, that cast iron, and one or two other metals, in the act of 

 solidifying enlarged so as to fill out sharply the minute parts of the mould 

 which was indeed the property on which their great u?c chiefly depended 

 were not :it variance with his general principle. Mr. Nasmyth replied, that, 

 so far from that, they were the mo<t striking examples of its application. 



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