Royal Irish Academy. 143 



tion by the evaporation of the naphtha from amongst its particles. 

 But the cases of aggregation of solids, without such elevation of 

 temperature, or the presence of solvents, are so rare, that but two or 

 three have as yet been observed. Of these the most remarkable is 

 that recorded by Pouillet, of the gradual, but complete, adhesion of 

 surfaces of clean plate-glass, when left to repose on each other for 

 a considerable time. It has also been stated, that clean plates of 

 lead or of tin, if pressed together by a considerable force when cold, 

 require a proportionably great force to separate them. The case 

 presented to the Academy, therefore, is another added to these rare 

 instances of molecular aggregation in solids, independent of solution 

 of fusion : the author therefore thought it worth while to examine 

 with a little care the properties both of the original brass, and of 

 the mass thus curiously formed from it, or, as he thenceforth called 

 them, of the normal and the anomalous alloy. 



The normal alloy is of a bright gold colour, and sub-crystalline 

 in structure, and of great toughness ; its cohesive force is equal to 

 21*8 tons per square inch, which is above the average strength 

 of any of the alloys of copper and zinc, or copper and tin, as found 

 by my experiments on the cohesive power of these alloys, published 

 in the Proceedings of the Academy, and elsewhere. The cohesive 

 force of the anomalous alloy is only T43 ton per square inch, or 

 only about one-fifteenth that of the former. 



The specific gravity of the normal alloy is = 8" 600; that of the 

 anomalous only = 7 '581. 



On submitting both alloys to analysis, their constitution proved 

 identical ; it is as follows : — 



Copper 83-523 



Tin 8833 



Zinc 7-510 



Lead 0-024 



Loss 0-110 



100000 



Uniting the small amount of lead with the tin, and dividing by the 

 atomic weights, the nearest approach to atomic constitution is, — 



Copper = 26" 3 atoms. 



Zinc = 2-3 ... 



Tin = 1-5 ... 



These alloys have therefore not a strictly definite constitution, but 

 one more nearly so than is usually found in commerce. 



Both alloys are equally good conductors of electricity. The 

 author examined their relative powers of conducting heat by the 

 method which Despretz has employed with so much accuracy, and 

 found that of the normal to that of the anomalous alloy as 36 : 35, 

 numbers which are so nearly equal as to render it likely the differ- 

 ence is only error of experiment. He also endeavoured to deter- 

 mine their relative specific heats, using the method of mixture, which 

 was the only one which the small size of the metals permitted, and 

 eliminating the errors incident to this mode by first plunging the 



