1823.] Mr. Longmire on the Congelation of the Metals. 343 



Article IV. 



On Reaumur's Experiments on the Congelation of the Metals. 

 By Mr. J. B. Longmire. 



(To the Editor of the Annals of Philosophy.) 



SIR, April 3, 1823. 



The experiments of Reaumur on cast-iron, bismuth, and anti- 

 mony, lead to the conclusions, that these metals expand during 

 congealation, and are lighter when solid than when fluid. But 

 as such conclusions are at variance with the general law, that 

 heat expands all bodies whose natural state is solidity, it becomes 

 important to show, that Reaumur's experiments do not militate 

 against this law. 



Reaumur found that the metals just mentioned, when fluid, 

 supported bodies specifically heavier than themselves in the solid 

 state ; so that they should have contracted in melting, and 

 would expand again in cooling. 



A floating body is lighter than the fluid that supports it, pro- 

 vided such Jiuid be quiescent. None, however, of the melted 

 metals, if exposed to the air, have the requisite degree of still- 

 ness, to form the fluid medium for obtaining accurate specific 

 weights ; but least of all, have cast-iron, bismuth, and antimony ; 

 metals that cool quickly, and that are in violent agitation, when 

 passing down to the point of congealation. Fluid iron, for 

 instance, has on its surface, bright glowing waves, rapidly 

 repeated in variable situations ; the hottest particles from below 

 rise to the surface in these waves shed laterally to cool, and 

 while they sink, others ascend, and give out part of their heat : 

 this motion is repeated till the iron begins to consolidate. The 

 other metals before-mentioned are nearly as much disturbed in 

 cooling as fluid iron ; hence in this state they are all too much 

 agitated to determine with accuracy the difference of density 

 between their solid and fluid states. So it follows that Reau- 

 mur's experiments depending on the aptitude of those melted 

 metals for this purpose, are inconclusive, and cannot be consi- 

 dered as proving any thing against the general law, that all 

 bodies, whose natural state is solidity, are heaviest in this state, 

 and expand on receiving heat. 



The force of the ascending particles in the melted metals 

 before-mentioned, will account for the extra specific weight of 

 the bodies that they support. But the amount of the ascentional 

 force is not determinable ; and whether these metals contract or 

 expand in cooling is not yet shown by experiment. Such an 

 experiment indeed is not easily performed ; but to reconcile 

 demonstratively the congealation of these metals with the law 

 regulating that of all the others, is a desirable and important 

 undertaking. 



