Zoology. 369 



In all these substances it is the small crystals which possess the greatest 

 specific gravity, whence it follows that they have the greatest homogeneity, 

 and that large crystals have in their interior vacuities more or less con- 

 siderable. 



The lamellar structure diminishes the specific gravity 0.0173 : The 

 fibrous structure with parallel fibres about 0.0177 : The structure with 

 diverging fibres 0.0186 : The structure with interlaced fibres 0.0312. 



The lowest specific gravities appear to take place in the epigenous va- 

 rieties of different substances. 



But all the varieties of the same substance present the same specific 

 gravity when they are reduced to powder. Hence it is clear, that, if we 

 wish to make specific gravity a comparable character, it is the absolute 

 specific weight that we must use, and not the weight relative to the exter- 

 nal volume which the substance occupies, as has hitherto been done. The 

 specific gravity of the powders is always a little less than that of the small 

 crystals, which arises probably from the production of some fissures in the 

 particles while pounding the body. 



According to my experiments, the following are the comparable specific 

 gravities of the above eight substances : 



Carbonate of lime, - - - 2.7321 



Arragonite, - - - 2.9466 



Malachite, - - - 3.5904 



Carbonate of lead, - - . - 6.7290 



Sulphate of hrae, - - - 2.3316 



strontian, - - - 3.9592 



Galaena, - - - 7.7592 



Quartz, - . - 2.6540 



ZOOLOGY. 



9. Captain Browns new work on Horses.'^'We are informed that Cap- 

 tain Brown has in the press, a work to be entitled Biographical Sketches, 

 and Authentic Anecdotes of Horses ; with a Historical Introduction, and 

 an Appendix on the Diseases and Medical Treatment of the Horse. It is 

 to be illustrated by figures of the different breeds, and portraits of celebra- 

 ted or remarkable horses ; these are to be engraved on steel by Mr liizars 

 in his best style. This Work is intended as a companion for the work on 

 dogs, by the same Author, recently published, which has deservedly met 

 with so favourable a reception. 



10. Notice regarding the Male and Female Orang-outang in the pos' 

 session o/*George Swinton, Esq, of Calcutta, in a letter to Dr Brewster, 

 dated 13th June 1828. 



" Last year I sent you an account of my orang-outang ". I have lately 

 got a female companion for him, apparently of the same age. She wants 

 the thumb nails of the lower extremities, which confirms me in the opi- 

 nion that this is a distinction of sex, not of species. The young female 



• See this Journal, vol. ix. p. I. 

 HEW SEEIES. VOL. I. NO. II. OCTOBER 1829. A & 



