246, Third Supplement to Dana's Mineralogy. 



Art. XXII. — Third Supplement to Dana's Mineralogy ; by the 



Author.* 



Since the last Supplement was issued, but few new species 

 Lave been proposed and several of these are of doubtful stand- 

 ing. The work of Professor Scacchi of Naples on the recent 

 eruption of Vesuvius (1855) contains many facts of special in- 

 terest, respecting the minerals produced at that time ; and one 

 of the varieties mentioned is an example of remarkable crystal- 

 lization. The crystals are octahedrons of magnetite implanted 

 on scoriaceous lava; but they are intersected throughout in the 

 four cleavage directions by lamina? of hematite (specular iron). 

 These laminae are thin crystals and have regular facets on the 

 edges, although so delicate as to require a glass to distinguish 

 them. Having received specimens from Professor Scacchi, the 

 author can attest to their perfection and the exact parallelism of 

 the 1 ami na3 to the faces of the octahedron. 



In American mineralogy, there has been the publication of 

 some geological reports containing information on useful mine- 

 rals and ores, and a few articles in the Journals. The only new 

 minerals have been announced in a mining report, and in this 

 volume (p. 96), by Prof. C. U. Shepard. 



It is a matter of regret that mineral species are so often 

 brought out, especially in this country, without sufficient inves- 

 tigation and full descriptions. It is not meeting the just de- 

 mands of the science of mineralogy to say that a mineral has 

 probably certain constituents, or to state the composition in a 

 general way without a complete and detailed analysis ; especially 

 when there are no crystallographic characters to afford the spe- 

 cies a good foundation. We have a right to demand that those 

 who name species, should use all the means the science of the 

 age admits of, to prove that the species is one that nature will 

 own, for only such belong to science : and if enough of the 

 material has not been found for a good description, there is not 

 enough to authorize the introduction of a new name in the 

 science. The publication of factitious species, in whatever de- 

 partment of science, is progress not towards truth, but into re- 

 gions of error ; and often much and long labor is required be- 

 fore the science recovers from these backward steps. 



1. List of New Works. 



Dr. Carl Friedrich Natjmann (Liepzig) : Elemente der theoretischen Krystallo- 

 graphie, 384 pp., 8vo, with 86 -wood-cuts. Liepzig.-— This volume is properly a 

 supplement to the former one ( Anfangsgrunde der Krystallographie) published in 

 1854. In that, the elements of the science are explained and the formulas for calcu- 



* For Supplements I and II, see this Journal, xix, 353 (May, 1855), and xxi, 193 

 (March, 1856). The paging inserted beyond, refers to the Mineralogy, 



