6ia PHILOSOPHICAL TRANSACTIONS. [aNNO 1754. 



but not thin; and lost about ^. The metal proved extremely hard to the file; 

 broke difficultly on the anvil ; flew asunder on endeavouring to cut it with a 

 chissel ; and appeared internally of a coarse grained texture and white colour. 



2. One ounce of platina and 2 of copper, urged with a quick fire in a blast 

 furnace, without addition, flowed sufficiently thin, and scarcely suffered any 

 sensible loss. The metal was still very hard, and yielded but little to the hammer. 

 It looked darker coloured than the foregoing, with a slight reddish cast. 



3. One ounce of platina and 4 of copper, treated in the same manner, united, 

 without loss, into a pretty tough compound ; which bore to be considerably flat- 

 tened, cut with a chissel, and bent almost double before it cracked. Internally, 

 it looked of a fine texture, and a very pale copper colour. 



4. A mixture of 1 oz. of platina and 5 of copper, stretched somewhat more 

 easily under the hammer than the preceding; and appeared of a redder colour. 



5. On increasing the copper to 8 times the quantity of the platina, the com- 

 pound proved sufficiently tough, broke difficultly, and hammered well. It was 

 much harder than copper, and of a paler colour. 



6. A mixture of 1 part of platina and 12 of copper was somewhat more easily 

 extended under the hammer than the foregoing, and proved softer to the file. 

 It stuck a little in the teeth of the file, which the compositions with a larger 

 proportion of platina did not. 



7. A mixture of 1 part of platina and 25 of copper was still a little paler co- 

 loured than pure copper, and considerably harder and stiffer, though very malle- 

 able. On increasing the copper a little further, the mixture retained a degree of 

 hardness, and appeared of a fine rose colour. 



8. On weighing the foregoing compositions hydrostatically, the diminution of 

 gravity was found more regular than in the mixtures with other metals, being 

 constantly greater in proportion as the quantity of platina was larger. 



Specific gravity. 

 By experiment. By calculation. DifFerenc©. 



