128 Geological Collections. 



pipe it fuses, gives off water, and leaves a black button, having the metallic 



lustre. The primitive form is an oblique rhomboid of 62° 30' and 117° 30'. 



The details of the analyses are given in the An. de Mines, VII. p. 139. 



Analysis of Brewsterite Mr Connell has published an analysis of Brew^s- 



terite from Strontian, in the last number of the Ed. New Phil. Journal. 

 He has found it to be composed as follows : — 



Connell. Retzius. 



57.285 

 17.011 



15.074 '^'l^l 7.764 



Lime 



17.872 

 100.454 99.932 



From which he deduces the formula -g S '^ -f 4 A S ^ + 6 aq. The for- 

 mula deduced by Retzius, from the results he obtained, as stated in the 

 second column, was jf S -"^ + 4 A S ^ + 8 aq. 



We have to object to this analysis, first, That it was made on a portion 

 of the mineral, only partly crystallized ; second, That requisite care does not 

 seem to have been taken in determining the amount of water, of which Mr 

 Connell is himself so far in uncertainty, that he says, only, " that if no- 

 thing but crystals were analysed, the proportion might be still greater, though 

 it is not likely that it would be so great as shewn by Berzelius' formula;" and, 

 thirdly. We have to object that Mr Connell has not given us numerical Aetaxls 

 of the results of his different analytical steps. If this be thought necessary 

 from chemists of established name, that their results may be proved, how 

 much more from young men, who have yet a name to acquire ! 



New variety of Mineral Resin Mr Johnston has described a variety of 



mineral resin, having much the appearance of amber, found in an old lead 

 mine in Northumberland, in the neighbourhood of a trap vein, imbedded in 

 solid brown spar, and carbonate of lime, as if it formed part of the solid 

 rock. It has the following properties ; — 



" Colour. Externally, red of various shades, black, and sometimes pale 

 yellow, approaching to the colour of amber. Internally, red, or brownish- 

 red, except in the yellow varieties, and by transmitted light of a brilliant 

 deep red colour. It yields to the knife, but is hard, brittle, and has a bright 

 glassy small conchoidal fracture. The fragments are transparent, and the 

 fractured surfaces exhibit a pale greenish tinge, (an opalescence) which 

 becomes more decided after the lapse of a few weeks ; the transparency at 

 the same time diminishing in a slight degree. 



" The specific gravity varies from 1.16 to 1.54 in the dark-red varieties. 



*' In the flame of a candle it takes fire, burns afterwards of itself with 

 considerable smoke, and an aromatic, slightly empyreumatic, odour, leaving 

 a small coaly residuum. 



" On the sand bath, in a close tube, it gives off a small quantity of a 

 transparent, colourless, and highly volatile naphtha, having a peculiar odour, 

 resembling that of some kinds of strong cheese. Heated to 400°, it does 

 not melt, but assumes a bright black colour, though, when broken into frag- 

 ments, it still transmits a rich red light. Over a spirit lamp it fuses, gives 

 off a colourless naphtha, a red empyreumatic oil, and leaves much charcoal. 



It is insoluble in water, and is very slightly acted on by alcohol or ether. 

 By hot concentrated nitric acid it is slowly, but entirely dissolved. 



" When rubbed, it exhibits strong negative electricity. 



" Dr Brewster informs me, that, like amber, it has no crystalline structure." 

 Brewster's Journ. of Science, New Series, No. VII. p. 122. 



