on some ancient metallic Arms and Utensils. 433 
primorum, et non prodibunt quatuor sed vix tres numero 
“ glcbuli, pondere quatuor globulorum reservato.” — 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 dimen- 
sions of these two metals on combination, cannot be so great 
as stated by Glauber. 
I made two ingots of tin and two 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 four ingots was 1730 grains. On combination by fusion, 
the compound afforded three ingots, and one-third of an ingot, 
of the same dimensions as the original ones; but those weighed 
only 1640 grains ; 90 grains 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 one-fourth of 
the sum of the bulks of the metals previously to fusion, ac- 
cording to Glauber ; but it might be about one-eighth. 
vii. 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 ren- 
der copper less oxidable by water, or atmospheric air ; to give 
hardness ; to render it sonorous ; to render it more fusible ; 
to produce a close texture and whiteness for reflecting light ; 
and to render copper less tough and clingy.* 
Copper allayed with one of the smaller proportions of tin 
by manufacturers, is metal of which guns or cannon, im- 
properly called brass guns, are made. Different proportions 
* The workmen say, claggy. 
3 K 2 
