Royal Irish Academy. 141 



properties of the equilateral hyperbola. These cases occur when, 

 the axis minor is a quadrant, and when the semi-axes a and b are 

 connected by the relation 



sin a = tan b. 



A notice of the occurrence of a Metallic Alloy in an unusual 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 qualities, which together constitute 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 con- 

 tinuity remains unbroken, which unites them in different directions 

 with the other classes of material bodies. Thus opacity, which is 

 probably mechanically destroyed in gold leaf, is lost in selenium ; 

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

 tellurium, selenium and sulphur, become translucent, and mingle 

 with the non- metallic elements. So also their solidity, at common 

 temperature, is lost in mercury ; their great density, in sodium and 

 potassium ; their malleability, in bismuth, antimony, and arsenic ; 

 while in tellurium, the power to conduct 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 qualities, those 

 which collectively belong to the same individual metal are as re- 

 markable for their permanence. 



Unless selenium be admitted to be a metal, no approach to di- 

 morphism 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 been given by him with 

 certainty, nor since verified by other observers. Hence any instance 

 of such a character, or tendency towards it, is worthy of attentive 

 consideration ; and it was with this view that the author brought 

 before the Academy the following notice of the occurrence of an 

 alloy of copper, in two states, having totally different sensible and 

 physical qualities, while identical in chemical constitution. The 

 alloy in question, in its original or normal condition, was in fact 

 a species of brass ; and the particular specimen presented to the 

 Academy was a portion of one of the brass bearings, or beds, in 

 which the principal shaft of a large steam-engine revolved. 



The bearing, or bed of a shaft (as is generally known), consists 

 of a hollow cylinder, generally of brass, divided in two by a plane 

 passing through the axis ; its inner surface is finely polished, and 

 sustains the shaft, during its revolution, which is also polished ; the 

 cavity of the brass being completely filled by the shaft, which, in 

 the present instance, was of cast iron, and about nine inches in 

 diameter. 



