74 G. F. Kunz — Mineralogical Notes. 



of colors equals in beauty that of any Mexican material, and it 

 is the first opal found in the United States that exhibits color. 

 Undoubtedly, better material of the kind exists where this was 

 found. 



Diamond. — During the summer of 1888 a small diamond 

 was said to have been found by Mr. C. O. Helm, on the farm 

 of Henry Burris, about three hundred yards from Cabin Fork 

 Creek, Russell County, near Adair County, Kentucky. While 

 walking through an old field, on the top of a hill, Mr. Helm 

 observed in the gravel, this small, bright stone, which on in- 

 vestigation proved to be a diamond, an elongated hexoctahe- 

 dron, with curved faces, lustrous, but slightly off -color, weigh- 

 ing 7/16 carats. The rock in the vicinity is said to be com- 

 posed of granite dykes, slates, and some floating rocks, such as 

 quartz, feldspar, magnetic iron ore, flint, garnet, etc., mingled 

 in clayey hills. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the action of Hydrogen peroxide on Chromic acid. — 

 Berthelot has investigated the reaction which takes place when 

 hydrogen peroxide is mixed with chromic acid or a chromate, 

 and finds that if no excess of acid is present a given quan- 

 tity of chromate can decompose an unlimited quantity of per- 

 oxide, and this without suffering itself any apparent change. This 

 result he accounts for upon the supposition that an unstable inter- 

 mediate product is continually formed and decomposed. When 

 solutions of the peroxide and potassium dichromate are mixed 

 together, and as soon as the mixture has become dark brown in 

 color, ammonia is added, a brown precipitate falls, which contains 

 hydrogen peroxide, chromic acid and chromic oxide. It is very 

 unstable, evolves oxygen even when washed with water, and 

 gives a yellow filtrate containing chromate. The small residue 

 finally left undissolved, contains the same constituents as the 

 original precipitate but in quite different proportions. — C. H., 

 oviii, 24, 157, 411; Ber. Berl. Ghem. Ges., xxiii, Ref. 217, May, 



1889. G. F. B. 



2. On the Atomic Mass of Chromium. — The atomic mass of 

 chromium has been determined by Rawson by means of am- 

 monium dichromate, using two methods. The first consisted in 

 igniting this salt, measuring the nitrogen evolved and weighing 

 the chromic oxide remaining. The second depended upon the 

 reduction of the dichromate with alcohol and hydrogen chloride, 

 and the determination of the chromic oxide precipitated by am- 

 monia. The first method, though simple in theory, did not prove 



