224 TRANSACTIONS OF THE [aPRTL 19, 



amount of the other diamond; the great resistance in the polish- 

 ing really occurring when the stone is put on the wheel. This 

 stone was put on the wheel March 10, 1885, and remained on 

 over 7-^ hours each day until November 15, 1885, It was 

 also placed on the wheel' another month during February, 1886. 

 The wheel made 2,800 revolutions per minute, and each revolu- 

 tion gave a trifle over 3 feet of travelling surface. The total 

 amount of travelling surface was 170,000 miles, equal to about 

 seven times around the earth. The result of this was the im- 

 perfect polishing of one square centimetre of surface. Upon an 

 ordinary diamond at least one hundred times as much effect 

 would have been produced. 



B. A fifth mass of meteoric iron from Augusta Co., Va. 



This mass of meteoric iron was given to the late Colonel W. 

 B. Baldwin, of Staunton, Augusta County, Virginia, and was 

 found at or near the place where the largest of the three 

 masses from Augusta County, first described by Professor Mallet,' 

 was found. Col, Baldwin was under the impression that it was 

 a detached part of the largest mass. Prof, Mallet received it from 

 him at a considerably later date than the large mass, and liaving 

 chipped and filed a small flat surface, he found, after etching, 

 the Widmanstattaii figures, like those on the large mass, A 

 careful examination has satisfied him that this piece of iron has 

 not been in any way artificially detached from any one of the 

 previously discovered masses, though there is no doubt that all 

 the other four meteoric irons from Augusta Co., including the 

 one now described, are portions of a meteorite which probably 

 exploded in mid-air. Its }n-esent dimensions are 8,5 cm, by G.5 

 cm., 7 cm, at the widestend, and 3 cm, at the smaller end. This, 

 like the other masses, contains ferrous chloride, which, from its 

 solubility in water, has caused much of the mass to exfoliate 

 and crack off, so that this mass is only a nodular remnant of 

 what was formerly a much larger mass. At one end there is a 

 large fragment weighing several hundred grams, that is in part 

 separated by a fissure 4 mm, wide — a result of oxidation. Tiie 

 following analysis of the mass is kindly furnished by Prof. J. 

 W. Mallet. 



Iron 90.298 



Nickel 8.748 



Cobalt .486 



Copper .016 



Tin .005 



Amer. Jour, of Science, 3 Series, Vol. xv., pp. 33'7-338. 



