VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. 53 



buli, pondere iv globulorum reservato. 1 ' — Glauber, de Furnis, pars iv. p. 67. 8vo. 

 1651. 



The specific gravity of the allays of copper by tin, and the following experiment, 

 show that the contraction in the dimensions of these 2 metals on combination, can- 

 not be so great as stated by Glauber. I made 2 ingots of tin and 2 of copper, of 

 nearly the same figure and dimensions. The specific gravity of the tin was 7*233, 

 and that of the copper was 8.594. The absolute weight of these 4 ingots was 1730 

 grs. On combination by fusion, the compound afforded 3 ingots and 4- of an in- 

 got, of the same dimensions as the orginal ones; but those weighed only 1640 grs.; 

 QO grs. being wasted and adhered to the melting pot. The specific gravity of one 

 ingot of this metallic combination was 8.340; and of another, 8.4. Consequently, 

 after making the most reasonable allowance for the errors of the experiment, the 

 contraction could not be -i-th of the sum of the bulks of the metals before fusion, 

 according to Glauber ; but it might be about -Lth. 



7- I next observe, that the proportions of tin found in the ancient metals consist 

 with the uses for which they were made. The principal uses of the allay of copper 

 by tin are, to render copper less oxydable by water, or atmospheric air ; to give 

 hardness ; to render it sonorous ; to render it more fusible ; to produce a close tex- 

 ture and whiteness for reflecting light ; and to render copper less tough and clingy, 

 or as the workmen say claggy. 



Copper allayed with one of the smaller proportions of tin by manufacturers, is 

 metal of which guns or cannon, improperly called brass guns, are made. Different 

 proportions of these 2 metals are used at different manufactories ; but I believe that 

 this gun metal seldom contains less than 1 part of tin to ] 2 of copper, nor more 

 than I part of tin to 9 of copper. Here as much strength, as is consistent 

 with the preservation of the figure of the instrument during its use, is required: 

 and if more tin were added, the gun would be liable to be fractured by the explosion ; 

 and if less were added, it would be liable to be bent. 



Copper allayed with a somewhat larger proportion of tin than in gun metal in 

 general, affords a metal sufficiently hard and strong for chopping tools, for many 

 useful purposes. Of such proportions, namely, about 8 or 9 parts of copper and 1 

 part of tin, there is very little doubt all the ancient nations, who were acquainted 

 with the allays of copper by tin, generally made their axes, hatchets, spades, chizzels, 

 anvils, hammers, &c. These metals, united in these proportions, I believe would 

 afford the best substitute known at this day for the instruments just mentioned, 

 now commonly made of steel or iron. Accordingly, before the art of manufactur- 

 ing malleable iron from cast iron was known at all, or at least practised extensively, 

 that is, till within these last 4 or 500 years, the allays of copper by tin must have 

 been very generally employed. The celts may be considered as specimens of the 

 kind of metal tools in general use before the art of manufacturing iron in the man- 

 ner just mentioned was discovered : for, as hath been remarked in a former part of 

 this paper, the celts seem to have been generally neither more nor less than metal 



