1 882.] Mineralogy. 837 



Falls, Connecticut. The foliated chlorite known as diabantite 

 frequently decomposes and then contains amygdules filled with a 

 bronze-yellow substance which exfoliates largely before the blow- 

 pipe. The diabantite itself is regarded as an original product of 

 the decomposition of the trap while still hot, while the so-called 

 diabantite-vermiculite is of much more recent origin, being due 

 to atmospheric alteration. 



Salt water in Sulphur Crystals.— Many of the flat crystals 

 of sulphur from Catania, Sicily, contain enclosures of a colorless 

 transparent liquid, in which gaseous bubbles may frequently be 

 seen. Microscopic tubular cavities also traverse the flat laminae 

 of the crystalline masses of sulphur. Sylvestri finds the enclosed 

 liquid to be a weak aqueous solution of sodium chloride and 

 sulphate, with traces of potassium, calcium, barium and strontium 

 chlorides. The total saline matter amounted to slightly over 

 one per cent. 



The Dispersion of Chromate of Soda. — M. Wyrouboffhas 

 shown that crystals of chromate of soda having four per cent, of 

 water have very remarkable optical properties. When examined 

 with converging polarized light a plate of this salt shows a curious 

 system of curves very differently arranged on either side of the 

 bissectrix. In the last number of the Bulletin of the Mineralogi- 

 es] Society of France, colored plates are given illustrating the 

 irregular figures produced by polarized light. The irregularity 

 of the curves is due to inclined dispersion combined with con- 

 siderable difference in the position of the planes of the axes for 

 different colors. It is a very striking example of inclined disper- 

 sion, no other substance being known to possess it to such a 



Aluminium as a Blowpipe Support.— The use of a plate of 

 aluminium as a support for the assay in blowpipe operations, as 

 advocated by Col. W. A. Ross, appears to possess a number of 

 advantages over the usual block of charcoal. 



The black sublimates formed by arsenic, antimony, lead, etc., in- 

 visible upon charcoal, can be distinguished upon the new support. 

 Any sublimates formed can be scraped off in a pure condition for 

 further examination, whereas upon charcoal there is always an 

 admixture of ash. The danger of loss of the sublimate or assay, 

 either by cracking of the charcoal, by blowing away, by admix- 

 ture with white ash, or by re-sublimation on the incandescent 

 charcoal, is greatly lessened by the use of aluminium as a support, 

 and more minute quantities of a substance may thus be detected. 



In practice, it is often necessary to place a small slip of char- 

 coal between the assay and the aluminium plate, in order to ob- 

 tain a sublimate. 



The superior heat conduction of aluminium prevents it from 

 combining with fusible metals, as is the case with platinum. For 



