W. E. Hidden — On Hanhsite. 133 



carbon loop in an exhausted vessel raised to such a point of 

 incandescence that it will radiate a definite amount of energy — 

 this energy being measured by a bolometer strip or the ther- 

 mopile at a definite distance from the carbon loop, and also 

 being measured by the formula JH = C 2 R^ would have a greater 

 range than an incandescent strip of platinum placed in free air. 

 The latter method, however, for the incandescence which pro- 

 duces a light similar in color to that of a sperm candle, is 

 extremely sensitive, and can be made, I think, more exact than 

 present photometric tests. Both methods have the great 

 advantage of substituting a measure of energy for a relative 

 indication by the eye, which is not connected with any absolute 

 measurement. 



These remarks apply to the question of a standard of light 

 for practical purposes, which shall also be scientific in so far 

 that more refined scientific investigation can connect this 

 standard at any time with more precise methods of measuring 

 the exact amount of heat given by radiations of definite wave- 

 length. By means of a Eowland concave grating and with a 

 bolometer strip, one can at present measure the energy of 

 definite radiations. We can say that our scientific standards 

 for light of different colors shall be based upon the energy 

 received upon a definite surface at definite points in the diffrac- 

 tion spectrum. 



Jefferson Physical Laboratory, Harvard College. 



Art. XIX. — On Hanksite, a new anhydrous sulphato -carbonate 

 of sodium, from San Bernardino County, California;* by Wm. 

 Earl Hidden. 



In the very complete and attractive exhibit of California 

 minerals brought to the World's Industrial and Cotton Centen- 

 nial Exposition at New Orleans, by Professor Henry G-. Hanks, 

 State Mineralogist of California, were several species of unusual 

 interest. Among these was the new borate, colemanite, in 

 large and brilliant crystals, much resembling the finest of the 

 Bergen Hill datolites ; also the new vanadium mica, roscoelite, 

 mixed mechanically with much native gold between the folia ; 

 borax crystals, clear and bright, of unusual size ; stibnite in 

 fine crystals almost equalling the late discoveries in this species 

 in Japan, and many others equally noteworthy. 



Of particular interest to the writer was a small lot of appar- 

 ently hexagonal crystals to which had been given the name of 

 thenardite. Now as thenardite crystallizes in the orthorhom- 

 bic system, I was prompted to question the correctness of this 



* Read before the New York Academy of Sciences, May 25, 1885. 



