476 Intelligence and Miscellaneous Articles. 



one of M'hich an air blast from a revolving fanner is projected through 

 the coke, with which the whole tube is tilled. The flame passes out 

 at the opposite hole, through a tube so contrived, as to heat the blast 

 of air to a temperature of 500°, just before it enters the coke fire. 



" ITie light from the former lateral aperture is that proposed to be 

 used, and issues through a plate of mica or glass opposite to it. This 

 aperture forms part of the conductory tube for the blast, which (by 

 passing into the coke in a direction opposite to that in which the light 

 is emitted) keeps the illuminating surface of coke clear from ashes ; 

 these are received below the grating, and by a diversion of part of 

 the blast, are blown into the chimney which receives the other pro- 

 ducts of the combustion. 



" As the vertical tube is close above, the combustion cannot pro- 

 ceed upwards, while the coke with which it is filled constantly drops 

 down to supply the place of that consumed, on the principle of the 

 ancient furnaces, called ' athanors' by the earlier chemists. 



" The only difficulty to be apprehended in the use of coke, is the 

 collection of slag from the fusion of its earthy and ferruginous con- 

 stituents ; however the author does not consider that this accumu- 

 lation during the period from sunset to sunrise, in mid- winter, would 

 materially interfere with its action." 



19-621 



ON THE COMPOSITION OF IDOCRASE. BY H. HESS. 

 Mineralogists have not yet hitherto agreed as to the composition 

 of idocrase ; only so far is certain, that many consider the chemical 

 formulse to be the same as that of garnet. Under this idea garnet 

 and idocrase are considered to be the same substance under two dif- 

 ferent forms. However this is not the case. Possessing a very fine 

 crystal of idocrase from Slatoust, I gave it to one of my best pupils, 

 M. Ivanor, to analyse. The following is the result of his analysis : 



Oxygen. 



Silica 37-079 containing 19-262 



Alumina 14-159 „ 6-612) 



Lime 30-884 „ 8-644 ) V 



Protoxide of iron 16-017 „ 3-646 V 13-009) 



Magnesia 1-858 „ 0-719 3 



99-997 

 which gives exactly 2(Ca' Fe^ MgS) Si + Al Si. 



We therefore possess three mineral species which only vary in the 

 number of their compounded elements, viz. 



Garnet K^ Si + Al Si 



Idocrase 2 Rs Si + Al Si 



Epidote R^ si -1- 2Ai Si. 



There can be no doubt as to the correctness of M. Ivanor's ana- 

 lysis, as it was performed under my superintendence and upon a 



