g^6 Scientific News, Accounts of Books, bfc. 



given by the celebrated Werner to the fubftance which we call Idocrafis. Citizen Hauy 

 has difcovered that thefe cryftals eflentially differ in ftrufture, as well as in their other 

 chara£lerlfl;ics, both from idocrafis and from brown tin grains, with which, at firft fight, 

 they might be confounded ; and that they belong to the zircon, of which they prefent a 

 new variety. Their fragments cxpofed to the flame of a candle, inftantly lofe their colour, 

 and this alfo is the cafe with fragments of zircon. Their primitive fliape, indicated by the 

 direflion of the natural jun£lures, is a re£tangular oftahedron, (Plate XXIV. Fig. 3,) 

 having the fame angles as thofe of the zircon, and like it, divifible by planes, which pro- 

 ceeding from the fummits, coincide with the bafes of the triangles, which form the faces 

 of the oftahedron. 



The variety of which he treats,' and which is reprefented by Fig. 3, has thi«ty.fix faces. 



Its fign is ' p. Citizen Hauy calls it iht JubtraEiive zircon , a denomination which 



he has adopted in cafes, like the prefent, where one of the exponents which accompany 

 the indicative letters, the letter E for inftance, is lefs by an unity than the fum of the 

 other exponents. 



The following are the meafures of the principal angles determined by the help of theo- 

 retical calculation. Incidence of / upon /, 90<^, of P upon/, i^\^ 25' of « upon P, i5o<i 

 5', and upon /, 1424 55', of k upon /, 159^ 17', and upon P 152'' 8'. > 



The length of one of thefe cryftals taken between the fummits of the two pyramids is 

 18 millimetres, and the thicknefs 8 millimetres. Their colour is brown, mixed with 

 orange ; they are tranfparent, and they contain billllant fpangles, interfperfed through 

 their fubftance, which give the appearance of an aventurine. 



Bulletin des Sciences, No. 39, p. 16. 



ExtraEi of a Letter from CiT. Hectb, jun. Apothecary at Strajburg, to Cij. VAUQ^VEtin. 



I lately received a letter from M. Klaproth, in which he informs me, that having pur- 

 chafed at the fliop of M. Hahneman, a certain quantity of the new kind of fixed alkali, 

 which he pretends to have difcovered, he found, by analyfis, that it was nothing but re- 

 fined borax. 



Thus it is found, that this new fixed alkali, fo pompoufly announced in the Journals by 

 JA. Hahneman, under the name of pneum, and fold by him for twenty fraocs the Ounce, 

 is reduced by the analyfis of M. Klaproth to its proper value. 



Index 



