COMMITTEES ON BEHALF OF THE GOVERNMENT 229 



hands of the assayer, J. R. Eckfeldt. The report of the Director 

 of the Mint, James Pollock, contains a statement regarding 

 the nature of the experiments which were made with this bar, 

 the results obtained, and the conclusions derived therefrom. He 

 first remarks that experiments had been made two years pre- 

 viously to determine whether aluminum bronzes could be used for 

 medals, that they had resulted negatively, and that then the use 

 of such alloys for coins had been suggested. He continues : 



" A further series of experiments was therefore undertaken here, at the desire 

 of the Secretary of the Treasury and a committee of scientific gentlemen. The 

 latter forwarded to the mint a bar for this purpose, which, by assay, was found to 

 contain the proportion of nine parts copper to one of aluminum. Their directions 

 were closely followed and the principal results may be briefly stated as follows : 



" The aluminum bronze, in the proportion just stated, is very rigid under the 

 rolls, requiring many annealings, and liable to crack and break into plates of 



oblique fracture This hardness gives it a great advantage in wear. Coins 



of the cent size were made of this alloy, of legal bronze, and pure copper. The 

 three varieties placed in boxes and rapidly shaken for a long time, 33 treated equally 

 in all respects, lost by attrition in the following ratio: Assuming the aluminum 

 bronze as the standard of comparison, the legal bronze lost about three times, and 

 the copper about six times as much. This property, however, is of no great conse- 

 quence in coins of little value. 



" A point of much greater consideration is the avoidance or mitigation of the 

 tendency to change color and become foul from the usual causes, viz., the action of 

 oily and saline excretions of the hand ; the chemical agencies which are met with in 

 market-stalls, and the slops of drinking saloons, and the mere exposure to air and 

 moisture. If any metal or alloy could be found that would look well, and keep 

 clean with the usage to which our small coins are generally subjected, it would be 

 deservedly popular. This can scarcely be expected. A silver coin can be deprived 

 of its original beauty and become of such a hue as to have its genuineness called 

 into question. Pure aluminum, white at first, assumes a bluish tint by atmospheric 

 action; and aluminum bronze, although closely resembling gold at first, was 

 found, after being held in the sweaty hand for a few hours, to have received an 

 ugly tarnish which destroyed the .last argument for employing it in currency. 



" After these experiments were concluded others were started, in the hope of 

 finding a binary or ternary alloy which would answer the required conditions, 

 especially as to ductility and keeping color for coins of a grade a little above the 

 cent and two cent pieces. After some progress had been made, it became evident, 



**This experiment was suggested by Joseph Henry. 



