198 F. A. Genth — Contributions to Mineralogy. 



A comparison of the results of table 2 and table 1 shows 

 that the latter substantiates and emphasizes the results of the 

 former. In table 2, moreover, the measurements of the effects 

 produced by stretching the same metal are in very much better 

 accord. It is not improbable that the variations of FJFfor 

 the same metal in table 2 may be due to actual differences of 

 hardness or composition of the annealed wires. 



In case of iron two values of P occur, and the metal 

 exhibits striking differences of behavior in the two experi- 

 ments. It appears that more energy is potentialized during 

 initial than during final stages of strain. For P = 40 kg, the 

 small value of t is only measurable as a superior limit. More- 

 over the extension is here so small that the error due to resili- 

 ence may be 5 per cent. 



6. To summarize it appears that as much as one-half of the 

 work done in stretching up to the limit of rupture may be 

 stored up permanently ; that the amount of work thermally 

 dissipated varies considerably with the metal acted upon, being 

 very large for instance in case of copper (75 per cent), smaller 

 in case of brass (60 per cent) and of iron (50 per cent) ; that 

 in case of the same given metal the work done is very largely 

 potentialized during incipient stages of strain, and very largely 

 dissipated during final stages of strain. When stress of a given 

 kind is applied to diffeient metals, the total amount of energy 

 which can be stored per unit of section, per unit of length up 

 to the limits of rupture, may therefore be looked upon as a 

 molecular constant of the metal. Table 2 shows that in case 

 of. a wire about *16 cm thick stretched nearly to the limits of 

 rupture, at least 5 megalergs per centimeter will have been 

 stored in case of brass, and about 1 megalerg per centimeter in 

 case of copper. In iron -14: cri1 thick at least 2 megalergs per 

 centimeter are potentialized under the same conditions. 



Akt. XX YI. — Contributions to Mineralogy, No. 4A ; by 

 F. A. Genth. 



1. Gadolinite. — In the fall of the year 1888, Dr. A. E. 

 Foote sent me for identification a shining black mineral which 

 he brought from Burnett County, Texas. A preliminary ex- 

 amination, which I made, proved it to be Gadolinite, which, 

 excepting that from Colorado, described and analyzed by Mr. 

 L. G. Eakins of the U. S. Geological Survey, had never been 

 observed in this country. Since it became known that the 

 mineral brought from Texas by Dr. Foote was gadolinite, large 

 quantities have been obtained, some in crystals, weighing from 



