196 



REPORT 1877. 



Combining these results in the same manner as the others, we have a total 

 difference of 26°-3 0. in KMT'S m., which is at the rate of 1° C. in 3'J-S m., 

 or 1° F. in 72-5 feet. 



The near agreement of this result with that obtained from comparison 

 with the assumed surface-temperature is very satisfactory. The mean of the 

 two would be 1° F. in 74 feet. The rocks consist, for the most part, of 

 trachyte and greenstone. 



Dr. Schwartz concludes his Report with the suggestion that the heat deve- 

 loped by the decomposition of pyrites and galena, in scams which are not alto- 

 gether air-tight and water-tight, may possibly be utilized as a guide to the 

 whereabouts of metallic lodes ; and that " we shall thus obtain, by means 

 of the thermometer, scientific information which the ancients sought by means 

 of the divining rod." 



Thanks are due to Herr Antoine Pech, Ministerial Councillor and Director 

 of the Mines, and to Herr Edouard Poschl, Director of the School, for ener- 

 getic cooperation in this extensive and valuable series of observations. 



Mr. Lebour, having been requested to supplement the above resume of the 

 Schcmnitz observations by an account of the connexion (if any) between the 

 geological and thermal conditions of the several mines, as indicated by a 

 comparison of the Eeports of Dr. Schwartz and Professor von Liszkay, re- 

 marks : — 



" The rock at all the mines except Franzschacht is green hornblende- 

 andesite (in German Grunstein-Traclujt), a compact, fine-grained, crystalline, 

 more or less vitreous rock, containing crystals of oligoclase and hornblende, 

 but no quartz or sanidine. This rock is a good heat-conductor, with a con- 

 ductivity probably nearly approaching that of ' Calton trap-rock.' 



" The Franzschacht is sunk in rhyolite (a highly siliceous vitreous trachyte), 

 a rock the conductivity of which would presumably be nearly the same as 

 that of hornblende-andesite, probably a little greater. Elements of tempe- 

 rature-disturbance are, however, present in the form of thermal springs and, 

 possibly, in the proximity of a basaltic cone. Tbis last element of disturb- 

 ance is, I should imagine, a very doubtful one indeed, although Councillor 

 A. Pech appears to think it of importance. The rate of increase, as deduced 

 from observations in the rhyolite hero, was 1° C. for 40-55 metres, or about 

 1° F. for 74 feet. 



" The Eeport brings out strongly the important variations of rock-tempera- 

 ture, which may be, and are occasionally, generated by the decomposition of 

 metallic sulphides, a point which, I think, is here prominently mentioned for 

 the first time." 



At the request of Mr. Lebour, observations have been taken by Mr. 



