197 



the concrete course of mortar covering the earth iu which the 

 body reposed, which was broken up by the violaters of the 

 tomb. 



A notice of the occurrence of a Metallic Alloy in an un- 

 usual state of aggregation and molecular arrangement, was 

 read by Robert Mallet, Esq., M.R. I. A. 



Amongst the several classes of substances which chemistry 

 at present considers as simple, the metals stand preeminently 

 marked by their almost invariable possession of a nearly fixed 

 and striking group of sensible quaUties, which together con- 

 stitute the well known " metallic character." Some of these, 

 such as lustre and fusibility, are common to every metallic 

 body ; but by the occasional variation of nearly every other 

 sensible quality of the metals, the law of continuity remains 

 unbroken, which unites them in different directions with the 

 other classes of material bodies. Thus opacity, which is pro- 

 bably mechanically destroyed in gold leaf, is lost in seleuium; 

 and so, in this most prevalent of their properties, the metals, 

 through tellurium, selenium and sulphur, become translucent, 

 and mingle with the nonmetallic elements. So also their solidity, 

 at common temperature, is lost in mercury; their great den- 

 sity, in sodium and potassium ; their malleability, in bismuth, 

 antimony, and arsenic ; while in tellurium, the power to con- 

 duct electricity is nearly wanting; and, lastly, hydrogen, to 

 all intents a metal in its chemical relations, yet possesses not 

 a single physical quality in common with these, but exists as 

 an invisible and scarcely ponderable gas. 



But although different metals thus vary in sensible quah- 

 ties, those which collectively belong to the same individual 

 metal are as remarkable for their permanence. 



Unless selenium be admitted to be a metal, no approach 

 to dimorphism has hitherto been recognized in any body of 

 the class ; the only case recorded, that by Dufresnoy, of the 

 occurrence of cast iron in cubes and rhomboids, not having 



