On an Artificial Diopside Rock. 133 



The crystals of terpene hydrate have been measured by List 

 (Pogg. Ann. vol. lxvii. p. 364), by Rammelsberg (Crystallogr. 

 Chem. p. 406, and Suppl. p. 227), and by Arzruni, who has 

 also determined the optical characters of the substance. The 

 measurements made by me accord very nearly with those ob- 

 tained by Arzruni. 



The parameters of the crystal are 



a: b: c = O8082 : 1: 0-4788, 



the angles calculated from which elements, and the averages 

 of those obtained by measurement on four crystals (tw r o from 

 each source), form the two columns in the following Table: — 



Angles. By calculation. Arzruni. By measurement. 



am = 5l 3 30 51 3J 



mm! = 77 53 77 49 20 77 53 



mb = 38 56 30 38 56J 



ah = 64 26 30 64 26J 



kk = 51 8 51 18 



mo = 52 44 52 49 40 52 36 15 



ao =67 37 30 67 37£ 



oo' =44 45 44 38 30 44 49 



bo = 61 54 



ok = 28 6 28 1 30 28 



oo' =56 12 56 8 30 56 2 30 



The faces m give in general excellent images ; the faces o give 

 a banded image. Arzruni's parameters are 0*80722 : 1 : 0*47 640. 



XX. On an Artificial Diopside Rock formed in a Bessemer Con- 

 verter by Mr. Percy Gilchrist. By K S. MASKELYNE,i^.i?.xS.* 

 MR. MASKELYNE drew the notice of the Society to the 

 production of diopside on a considerable scale at Blsen- 

 avon by Mr. Percy Gilchrist and Mr. Sidney Thomas, during 

 some experiments those gentlemen conducted having in view 

 the elimination of phosphorus in the Bessemer converter. The 

 artificial diopside was produced in a downdraught kiln at a 

 very intense and prolonged heat — the kiln being lined with 

 silica bricks, which were in contact with a moderately alumi- 

 nous and siliceous magnesian limestone. The product result- 

 ing from the action of the bricks on the limestone occurs 

 in large masses, portions of which present the appearance of 

 an interlaced mass of glistening crystals of a grey hue. 



Here and there, in hollows, minute crystals are met with 



* Communicated by the Crystallological Society. 



