t82 On the Effe^ of a Mixture of Tin with GoM. 



pieces of this extremity of the ingot, there was one fufficiently long, though a little curled, 

 which I laminated a fecond time, with the determination of rendering it very thin without 

 the leaft annealing. It acquired at ieaft double the length it had at firfl: without breaking ; 

 and, if we except the two fides of this plate which were cracked, the body, or main piece, 

 was entire. It was fpongy, and might be confidered as if formed out of an ingot of com- 

 mon gold containing no tin, but not poiTeffing the whole of its natural du£tility. 



It follows, from thefe experiments, that gold, whether fine or alloyed, when perfe£lljr 

 fufed with a fmall portion of the fined tin, acquires rigidity and hardnefs by the mixture; 

 that it lofes fomewhat of its diftinguilhing colour; and that it may, indeed, by careful ma- 

 nagement, be extended to a certain degree by the hammer, or flill better by the rollers; but 

 that, as it cannot be annealed without danger of breaking, it is by this defect deprived of 

 the eflential advantage of recovering its original foftnefs after it has been flrongly hammer 

 hardened. It is not but by careful management in the ufe of the hammer, and by frequent 

 annealing, that artifts employed on works of gold and filver fucceed in obtaining them 

 without cracks, and bringing them to a ftate of perfeilion, without being obliged to have 

 recourfe to folder to repair the defe6ls which exceflive hardnefs under the hammer would 

 occafion. How much, therefore, ought gold-workers, who continually have this metal in 

 tlieir hands, to be attentive to prevent the introdudlion of tin in their workftiops, and never 

 to employ fuch compounds of gold as are fubje£l to break, or even to warp, while annealing? 

 The expence of refining, which they would pay for depurating fuch compounds, would be 

 of lefs confequence to them than the lofs of time required for the careful management of 

 fuch gold contaminated by tin, even if they did fucceed in ufing it, and were not often forced 

 to abandon, after much labour, a work nearly finiflied. 



I do not doubt but that Mr. Alchorne, if he had carried his experiments further, or had 

 confidered them with regard to the methods of gold-workers, who frequently expofe to the 

 fire fuch pieces as they propofe to raife or fafhion according to their defigns ;— 'I do not 

 doubt, I fay, but that Mr. Alchorne would have cautioned artifts againft the accidents to 

 which gold alloyed with tin is fubjeft while annealing. He has obferved a degree of duc- 

 tility in this matter, and has not prefumed that it might be taken away by means of fire, 

 which, on the contrary, reftores to moft metals their flexibility and facility of working. 



The opinion which has hitherto been maintained refpedling the danger of a very fmall 

 alloy of tin with gold is therefore well founded. In faft, it muft have been difficult for fuch 

 an opinion to have prevailed without foundation, when a multitude of artifts are in a fitua- 

 tion to verify the fad, and muft be Immediately ftruck with the brittlenefs of fuch gold, 

 and be moft ftrongly interefted to difcover its caufe. 



This example of an opinion generally received and fupportcd on conftant fails, which 

 the greater number of artifts have rather adopted than examined ; this example proves that 

 we ought not, without the greateft caution, to attack fuch received notions, particularly 

 when as in the prefent cafe it is in no refpe£l hurtful, and only tends to render the work- 

 men more cautious in the ufe of the moft valuable of metals. ♦ 



The experiments of Mr. Alchorne have long remained upon record in the Philofophical 

 Tranfa£lions, and have by that means acquired a fandion which demands a greater degree 

 of attention. I have had no other aim in repeating them, and exhibiting an efiential depen- 

 dant fad not mentioned by that flsilful aflayer, than to give ufeful information to artifts, 



and 



