52 PHILOSOPHICAL TRANSACTIONS. [ANNO 17g6. 



Malacca tin has not this property. These differences of properties most probably 

 depend on some extraneous matter ; but in so small a proportion as to have hitherto 

 eluded the research of analysis. 



In the case before us, it is probable that a very minute proportion of extraneous 

 matter was present in the spear-head and sauce-pan, especially as they were made 

 of cast metal ; which might be less hard, and less compact in texture, than an 

 allay of pure metals, containing a smaller proportion of tin to the copper, and yet 

 the allay might be less brittle than the cast metal. This extraneous matter may 

 be oxygen, or sulphur, or earth, though in an imperceptible quantity, introduced 

 during the fusion. The lituus is harder, and not more brittle than the spear-head 

 and sauce-pan ; though it contains less tin. It was made of a plate of metal which 

 had been much hammered, and must therefore either originally have been made of 

 purer metal than the spear-head and sauce-pan, or have been rendered purer by 

 hammering. Perhaps metals in general are rendered purer, more uniform in tex- 

 ture, and more dense, by re-melting, than they were immediately after casting from 

 the ore ; or in the case of steel immediately after cementation ; or in the case of 

 allays after the fusion by which the union was effected. Accordingly, cast iron is 

 rendered less brittle by repeated fusion ; Mr. Huntsman's cast steel is made by 

 merely re-melting steel which had been manufactured by cementation ; and Mr. 

 Mudge's speculum metal, an allay of copper by tin, was not uniform and suffi- 

 ciently compact till it was re-melted. The specific gravity of the sauce-pan, and 

 spear-head, was particularly increased by fusion, § 3, 2, 3 ; and their texture was 

 rendered more uniform and compact, § 2. 



The specific gravities of the ancient metals correspond, as nearly as should be 

 expected, with their composition found by analysis ; and agree sufficiently with the 

 synthetic experiments, § 3 and § 6. I did not find that the specific gravity of the 

 same metal, under known circumstances alike, was so nearly the same in all cases 

 as is stated by most writers. In the preceding experiments, different parts of the 

 same ingot varied more than is commonly supposed in point of specific gravity. 

 The specific gravities of the ancient metals, after melting, varied between 8.5 and 

 8.8, or nearly so; and the specific gravities of the allays of 3 to 20 parts of copper 

 with 1 of tin varied between about 8.5 and 8.9. These great specific gravities 

 seem surprizing, because that of tin is only about 7-2, and of copper ingot about 

 8.420. But of all metallic combinations that of copper with tin produces perhaps 

 the greatest increase of density. Aristotle made this observation long since *, and 

 the fact is familiarly known to manufacturers of bell-metal. But it does not ap- 

 pear that the increase of specific gravity is so great as it is stated by Glauber. 

 According to him, if 2 balls of copper and 2 bails of tin of the same dimensions 

 be melted together, the compound will afford scarcely 3 balls of the same dimen- 

 sions as each of the 4 balls ; and yet the 3 balls will weigh as much as the 4 balls. 



— " Funde praedictos globulos in unum iterum effunde mixturam liquefac- 



tam in typum globulorum primorum, et non prodibunt iv sed vix iii numero glo- 

 * Aristotle, IIEFI teneseqs kai 4>©OPAS to a. K«p. ♦.— Orig. 



