THE GREAT GEYSER. 25 



as to deter Mr. Des Cloizeaux from mentioning tlie discovery in his memoir 

 on the Great Geyser.^ He collected numerous specimens, however, some 

 of which he was kind enough to show me, and noted the conditions in 

 detail. During the last forty years quicksilver and its sulphides have re- 

 peatedly been discovered in close relations to thermal springs, and it no 

 longer seems intrinsically improbable that this occurrence was produced by 

 deposition from natural solutions. Indeed, it has repeatedly been referred 

 to in the later literature, though not by its discoverer, as if it were beyond 

 question a natural deposit. 



The basin of the Great Geyser is about eighteen meters in diameter, 

 and the point at which the quicksilver was found is within the rim exactly 

 due east, magnetic, from the vent. Traces of the metal were detected over 

 an ai-ea of about one square meter, and Mr. Des Cloizeaux roughly esti- 

 mates the entire quantity of mercury wliich he collected at about half a 

 pound. It occurred at depths from the surface of the sinter varying from 

 one or two millimeters to about four centimeters. The specimens which I 

 saw seem to show that the mercury was originally deposited in the me- 

 tallic state, for liquid globules of the metal about two millimeters or less in 

 diameter are often partially enveloped in crusts of black sulphide, mani- 

 festly produced by the action of soluble sulphides on the inclosed metallic 

 drops. Portions of the sinter, at some distance from visible globules of 

 quicksilver, -were stained black by mercuric sulphide, and at some points 

 small quantities of the red sulphide made their appearance. 



The fact that cinnabar accompanies this quicksilver shows that the 

 water of the geyser is capable of dissolving traces of mercuric sulphide; foi", 

 had not this been the case, only metacinnabarite could have resulted from 

 the attack of metallic mercury by soluble sulphides. The investigations 

 described in Chapter XV of this memoir also show that mercuric sulphide 

 is soluble to a considerable extent in waters of a composition similar to that 

 of this great spring. Such solubility is evidently a necessary condition of 

 the hypothesis that the mercury was deposited from the water. 



On the other hand, there are circumstances connected with the occur- 

 rence which seem to me to point somewhat strongly to an artificial origin. 



' Anuales de cliimie, Paris, vol. 19, 1847, p. 444. The information given in the text was verbally 

 communicated to me by Mr. Des Cloizeaux. 



