68 Mr. Haidinger's Account of the Specific Gravity 



taken care to employ specimens free from visible mechanical 

 admixtures. Too little attention has been bestowed by most 

 mineralogists on this important branch of the resources of 

 their science, and at a period of so assiduous labour as the 

 present is in mineralogy, we are often referred to the deter- 

 minations of Brisson or of Muschenbroek, in regard to the 

 specific gravities of bodies, of which either the species was not 

 correctly determined, or the great bulk employed in the ex- 

 periment rendered the purity of the mass very problematic. 

 Indications of this kind were taken upon authority, and trans- 

 ferred from one mineralogical work into another, but seldom 

 verified by subsequent observations ; nay, it happened some- 

 times, that even if there were correct statements existing, yet 

 erroneous ones have been ignorantly selected, and the de- 

 scription of the species deprived of one of its most essential 

 characters. 



I have arranged in the following list a part of a series of 

 observations which I lately had occasion to make, and which 

 were thought by some distinguished mineralogists to contain 

 some interesting information, as they are pure matters of fact, 

 relating to one of the most important departments of mineralo- 

 gy. The specific gravities were all taken by means of hy- 

 drostatic balances ; and, what is the most necessary precau- 

 tion in operations of this kind, the specimens were sufficiently 

 purified, and the air bubbles which adhere to them when 

 immersed in water disengaged. The numbers obtained by 

 experiments at different temperatures, I have reduced to that 

 of 15° centigr. or 59* Fahreu. by means of tables of the spe- 

 cific gravity of distilled water at different temperatures, pub- 

 lished by Dr. Young and Prof. Trallcs. Most of the experi- 

 ments were made with distilled water, or water obtained from 

 melting very pure snow, and a few of them with spring water, 

 from which the air had been disengaged. The difference in 

 the specific gravity of these fluids is so very slight, seldom 

 exceeding 0.001, that it will be of no consequence to leave 

 it out of sight, as in general the range of the specific gravi- 

 ties within a species is much greater than could be account- 

 ed for by the difference in the specific gravity of the water 

 employed for ascertaining it. The substances themselves are 

 disposed nearly in the order of the system of Professor 



