166 Geological Observations made ifi Scotland, 



on the mica, gave a well-characterised glass of litharge, and a minute 

 globule of pure gold. This interesting mineral has not, I believe, 

 been heretofore discovered in the United States, and it is extremely 

 rare in Europe. It had been mistaken for sulphuret of molybdenum, 

 and was considered to be of no value. That error should be cor- 

 rected, for it is not only valuable as an extremely rare mineral, but 

 since, as I am informed, it occurs in abundance in the Virginia 

 mine, it should be saved and wrought for gold, in the same manner 

 as is practised in the tellurium and gold mines of Transylvania. It 

 is very easy to expel the tellurium by heat, and then the gold may 

 be obtained by the usual processes of amalgamation by mercury, and 

 discharge of the mercury by heat. Since I detected the tellurium, I 

 have conversed with T. A. Dexton, Esq., of Boston, who has recently 

 visited the mine, and has seen a considerable quantity of this tellurium 

 ore in the vein. He gave me two very well characterised specimens, 

 which he took from the vein in place ; so there can be no doubt of 

 its existence in a true auriferous vein. 



I announced this discovery at the annual meeting of the American 

 Academy of Arts and Sciences last month. — American Journal of 

 Science and Arts, 2d Series, vol. vi., No. 17, September 1848, 

 p. 188., 



Geological Observations made in Scotland^ by Professor Stu-- 

 DER. Contained in a Letter to Professor Leonhard. 



Bern, April 25, 1848. 



The vievt^s at which I have lately arrived with regard to 

 the meaning of the cleavage of our gneiss and mica-slate 

 hills, made it highly desirable for me to become more inti- 

 mately acquainted with the researches of scientific men in 

 Britain on this subject. Mr Sharpe, in London, by his col- 

 lection of compressed specimens of Spirifer and Productus, 

 was so kind as to confirm and illustrate to me the results 

 already given in the Jahrbuch, to the effect that the distor- 

 tion is the greater the smaller the angle is at which the di- 

 rection of the cleavage cuts that of the stratification ; and 

 that all the compressions may be explained by a pressure 

 perpendicular to the cleavage- planes, and an extension in the 

 direction of their dip. With Darwin I had already discussed 

 these matters in correspondence ; and, during a short visit 

 to him at his country-seat in Kent, our conversation fre- 



