VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 623 



Exper. 3. 120 grains of fine tin were mixed with 12oz. of fine gold, and 

 being cast like the foregoing, produced a bar rather paler and harder than the 

 preceding, but which suffered the like operations very well ; except that, on 

 drawing between rollers, the outer edges were disposed to crack a little. 



Exper. 4. 140 grains, or half an ounce, of the like grained tin, were mixed, 

 as before, with 12 oz. of fine gold ; and the bar resulting from this mixture was 

 completely sound and good ; evidently paler and harder, however, than any of 

 the foregoing, and cracking rather more than the last on passing between the 

 rollers ; but bearing every other operation, even stamping under the press, by 

 the common force, without any apparent injury. 



Exper. 5. One ounce of tin was next stirred into 12 oz. of the like refined 

 gold, and then cast as before ; but the bar produced, though seemingly solid and 

 good, was bad coloured, brittle in texture, and, on the first passing between 

 the rollers, split into several pieces, so that no further trials were made with it. 



Exper. 6. To inquire how far the fumes of tin, brought into contact with 

 the gold, would do more than mixing the metal in substance, a small crucible, 

 filled with 12 oz. of standard gold, -fi fine, was placed in a larger crucible, 

 having 1 oz. of melted tin in it, and kept there in fusion, the whole being 

 covered with another large inverted crucible, for about half an hour. In this 

 time a full quarter part of the tin was calcined ; but the gold remained unaltered, 

 and equally capable of being manufactured as another portion of the same gold 

 melted in the common manner. 



It may well be asked, whether the tin, or part of it, in every trial, might not 

 be destroyed, and thus render the conclusions fallacious ? But as, in any of 

 these experiments, not more than 6 or 8 grains of the original weight were 

 missing after the casting, and as even fine gold can scarcely be melted without 

 some loss in the operation, so we may reasonably suppose, that our small losses, 

 in the foregoing trials, do not deserve consideration. The above experiments 

 then seem to show, that tin is not so mischievous to gold as hath been generally 

 represented. But it would be unfair to infer, that the original author of this 

 doctrine, from whom so many have implicitly transcribed, had no foundation 

 for the assertion. Gold and tin indeed are substances pretty well known ; but 

 it is easy to imagine, that coins or trinkets may have been used for one, and 

 impure tin, or pewter perhaps, for the other ; and it is difficult to guess what 

 might be the result of such uncertain combinations. To inquire further, there- 

 fore, the experiments were continued as follows. 



Exper. 7- To determine whether the two metals might be more intimately 

 combined, and the mass rendered brittle, by additional heat ; the mixture of 

 gold and tin, produced in the first of these experiments, was re-melted in a 

 stronger fire than before, and thus kept in fusion full half an hour. By this 



