specific Gravity , and comparative Wear of Gold. 75 
known, therefore made the following experiments, in order to 
investigate the subject in dispute. 
MR. BlNGLEY’s EXPERIMENTS UPON GOLD ALLOYED WITH TIN. 
I. 
«« Two bars of gold alloyed with tin, in the proportion of 
“ eight grains in the ounce Troy, and which had passed the 
« steel rollers without any disposition to break on the edges, 
“ were submitted to an annealing heat, under a muffle, at two 
“ different temperatures. 
“ The first bar was exposed to a low degree of heat, visibly 
“ red by daylight, which contracted Wedgwood’s pyrometer 
“ five degrees. 
“ At this temperature, the metal was sufficiently annealed, 
“ had lost the sonorous property acquired by passing the rollers, 
“ was quite ductile, and capable of being worked into any form; 
“ and was slightly discoloured or oxidized on the surface. 
“ The second bar was subjected to a somewhat greater heat, 
“approaching the cherry-red described by Mr. Tillet, and 
<e which contracted the pyrometer ten degrees. 
“ At this temperature, some sensible changes soon began to 
“ take place; and, by a constant attentive watching of the metal 
“ during this exposure, three gradations of mischief were evi- 
“ dently marked. 
“ 1st. Little distinct bubbles or blisters arose in different 
“ places on the surface. 
“ edly. The whole bar, in a short time, began to curl up, or 
“ warp, on the edges. And, 
“ 3dly. When the whole of the tin, diffused through the 
“ interior of the metal, might be supposed to be in fusion, a 
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