Scientific news. 239 



dependant on the facility -with which their practical means can of science from 

 be obtained. Less than thirty years ago there were not three and'sa^e^of the 

 places at which the ready prepared materiais of philosophical useful means 

 chemistry could be purchased in this great metropolis. There ° P'^acuce. 

 was but one maker of turning lathes ; philosophical instru- 

 ment makers were very few j and there were no steam engine 

 makers, agricultural implement manufactories, &c. in 

 London, with which we now so plentifully abound. I would 

 submit to your consideration. Sir, that he who establishes a 

 place of fabrication or deposit of an article of use to the 

 sciences, which could not before be purchased, is a benefactor 

 to the public y and under this point of view, I oiler you 

 tlje present notice, as a piece of scientific news, though it 

 is likewise of a private commercial nature. I have, with consi- 

 derable expense and attention, prepared a set of models of 

 crystals, partly solid and partly dissected ; and have made ar- 

 rangements, which enable me to supply the public. The dis- Dissected mo- 

 sected crystals are so constructed, that they can readily be taken ^^^^ ^ 

 to pieces and built up again in various ways, to give the un- 

 tutored eye a distinct conception of the laws of that geometry, 

 which are followed by the integrant particles when they com- 

 bine, and the orderly airaiigeraent of which produces symme- 

 trical crystals. And this in fact constitutes the basis of the 

 science. 



A single glance at the dissected models will enable the stu- 

 dent to comprehend why crystals are always rectilineal bodies, 

 bounded by planes ; and whence that immense variety of ac- 

 tually existing crystalline forms is derived, with which the mi- 

 neral kingdom has hitherto astonished the world. 



I have likewise composed a treatise, which will form a work Treatise refer- 

 distinct in itself; but nevertheless so composed, that it niay ^"ij 

 serve as an index of reference to its models through the work*. 



And as the series of solids to be finished on the present occa- Subscription 

 sion will be limited, such individuals, who are desirous of re- proposed, 

 ceiving sets of them, will have the goodness to favour the 

 author with their orders, either in a direct way, or through 

 the medium of their booksellers. 



*This work, which is In the press, will shortly be pubh'shcd byMes';rs. 

 Longman, Hurst, Rees, Orme, and Brown, Paternosrerrow. The copper 

 plates for the work are engraved by Lowiy ; au'l the linea! projections 

 hv Berryman and Brandfitone. 



This 



