1865.] Mining, Mineralogy, and Metallurgy. 121 



some years since portions of the human body most thoroughly silicified, 

 yet still retaining their natural colour. This process was lost, with 

 the inventor of it. M. Marini, however, supposes that he has redis- 

 covered the process of Girolamo Segato. It is stated that animal 

 substances are petrified most readily by simple immersion in the bath 

 of M. Marini ; that they retain their colour, and are rendered abso- 

 lutely indestructible. As an ingenious imitation of processes which 

 are constantly going on in nature, and which it serves to explain, the 

 announcement of this discovery finds a place in these pages. 



M. Kuhlmann read before the Academie des Sciences of Paris, 

 in October, the second part of his researches on " Crystallogenic 

 Force." He applies this name to the tendency which molecules of 

 the same nature have to form crystals. It is not a little curious to 

 find the researches of Dana entirely ignored, and his admirable essay 

 on Crystallogenic Force forgotten. The reader of Kuhlmann's paper 

 would suppose that the idea of this force, as an independent energy, 

 had originated with him, and that the name was his especial coinage, 

 whereas the American Mineralogist has employed the term for a long 

 period, in his large work, and has examined with great care, many 

 of the phenomena involved in the consideration. 



M. Kuhlmann's researches are of very considerable interest, and 

 are leading, it would appear, to a solution of some of the difficulties 

 which at present surround the laws by which crystallization, or the 

 natural grouping of molecules into a geometric solid, is produced. 

 The memoirs are too extensive to be reproduced, and they do not 

 admit of condensation. The student of this interesting brauch of 

 physical science is, therefore, referred to the journals of the French 

 Academy of Sciences.* M. Morin directed the attention of M. Kuhl- 

 mann to the spontaneous crystallization of iron — a question which 

 still requires a close and searching examination. In connection with 

 this, it may be noted that Mr. Paget, C.E., in May last, before the 

 Society of Arts, and lately a correspondent to the ' Engineer,' has 

 pointed out that wrought iron is rendered more or less brittle by 

 strains in excess of the limits of elasticity ; that a crystalline fracture is 

 produced by any sudden rupture ; that a state of brittleness, whether 

 due to defective manufacture or to excessive strains, would render a 

 bar peculiarly liable to rupture under impulsive forces ; that rupture 

 under such circumstances must be sudden, and, consequently, crystal- 

 line in appearance. 



At a more recent meeting of the Academie des Sciencs, M. Kuhl- 

 mann exhibited a great many reproductions — by photography, electro- 

 nietallurgy, and nature printing — of crystallizations upon glass plates, 

 and which he calls crystalline tablets. This is an especially inte- 

 resting mode of obtaining and preserving the forms of crystals for 

 study.f 



* ' Los Comptis Rendus.' ' L'Institut,' No. 1C06. ' Lcs Mondes, Revue 

 Hebdomadaire des Sciences/ Oft. fj ami 20, 1864. 

 t ' L Institut," No. 1607. 



