366 Notices respecting New Books, 



or England, and this circumstance has very materially ob- 

 srriicted the progress at" this interesting study , Some Italian 

 and Spanish professors have published brief outlines of it, 

 designed to facilitate its coniprehcnsion by their pupils ; 

 but a complete and elementary treatise on crystallography 

 is yet a desideratum in literature, Mr. A. might have ren- 

 dered this work still more useful, by devoting a chapter to 

 illustrate or rather to exhibit in a concise manner the ma- 

 thematical method adopted by Haiiy. Without some such 

 exhibition his work does great injustice to the illustrious 

 author of the erystallop^raphic system; it de£;rades the dis- 

 coveries and invei\tions of Haiiy ironi the exalted raiik of a 

 science, to that of a mere mechanical process of measuring 

 solids and angles. It is true, his plan is more simple; 

 but should his readers wish to consult the original Traite 

 de Alinaalogie, the surprise n;av perhaps deter them alto- 

 gether from pursuing the study further. The object of art 

 elementary work is to open the door to knowledge, not to 

 find a lazy substitute for it. But perhaps we should raihcr 

 be thankful to the author for what he has done, than 

 blame him for what he has left undone; a full knowledge 

 of mineral architecture is not lo be acquired at once. 



Mr. Aecum commences with a delinition of the term 

 crystal, the growth of crystals, and the ingenious opinion 

 of Dr. Young that crystallization is the universal cause of 

 solidity. The conditions of crystallizing bodies, and the 

 various causes which influence the process of crystallization, 

 are so intimately connected with chemistry, and still so 

 inadequately known, that it would require much time and 

 labour to develop them with any precision. A few ex- 

 tracts will convey an idea of the author's popular manner 

 of illustrating this part of his subject, which is well adapted 

 for exhibition in lectures to a mixed audience. 



Crysfuliizalion by reduction of temperalure. *' If we 

 melt a ladle full of bismuth, antimony, zinc, sulphur, or 

 muriate of lead, and allow it to cool slowly and quietly till 

 a thin crust has formed on the surface, and then by means 

 of a pointed iron make two small opposite apertures 

 through the crust, and quickly pour out by one, the fluid 

 portion as i arefuUv and with as little motion of the mass 

 as pos^ib!e, whilst the air enters by the other aperture, there 

 will appear on removing the upper crust with a chisel, when 

 the vessel is cold, a cup-shaped concavity studded with 

 crystals, very brilliant, and more or less regular, according 

 to the magnitude of the mass en)|)loyed, the tranquillity and 

 slowness v.ilh which it has cooled, and the dexterity v^'ith 



which 



