382 



KEPOET UNITED STATES GEOLOGICAL SURVEY. 



The average increase, as given by various authorities, is shown in the 

 following table: 



Kate of increase. 



Authority, i&c. 



10 F. for 50 or CO feet 



1° F. for 53 feet (1° in 30 to 1° in 90) 



1° F. for 27 feet 



1° F. for 45 feet 



1° F. for 24 feet 



1° F. for 51i feet 



lo F. for C6 feot 



loF. for 23 feet 



1°F. for 62 feet 



loF. for 68 feet 



Dana's Mantial of Geology, p. 699. 

 Elements of Geology. Le Cvinte. 



This is at Yakupkj Siberia, found by Magnus (quoted by Dana). 

 M. Cordier quoted by Lyell, in Principles of Geology, p. 539. 

 At Monte Masse, in Tuscany. (Judd's Volcanoes, p. 341.) 

 Professor Everett, from Observations on the Sperenberg Boring 



<depth of 3,390 feet.) 

 H. B. Medlicott (Observations on Underground Temperature. 



Rec. Geol. Surv, of India, vol. s, pp. 45^8) deduces this from 



temperatures at 350 feet depth in coal field of Sarepla. 

 At Budy Pesth. (.Judd's Volcanoes, p. 342.) 

 Report of the British Association forthe Advancement of Science, 



1881. 

 Report of the British Association for the Advancement of Science, 



for 1879. 



The rate of increase does not follow the same law in all parts of 

 the earth. Some writers think it increases to a certain depth and 

 then begins to decrease again. Everywhere, however, that observa- 

 tions have been made there appears to be an increase as we descend 

 towards the center of the earth. In this increase of heat, of course, 

 we have sulficieut reason for the heat of springs coming from a great 

 depth. In many thermal springs, however, as in our Yellowstone 

 region, this regular increase in temperature is not sufficient to account 

 for the high temperatures, and we must look for the cause, in pli- 

 cations, and faults, or in the volcanic rocks in which the springs are 

 located. The intimate connection of hot springs and volcanic action 

 has long since been noted. In Part II we have traced this connection 

 around the globe and found it existing in evcT-y land. No boiling 

 springs exist in other than volcanic regions — i. e., where there are vol- 

 canic rocks. The rocks need not be geologically recent, for in the 

 Yellowstone Islational Park they are, in part at least. Tertiary in age, and 

 yet we have some of the hottest temperatures knorrn anywhere. In Ice- 

 land and in New Zealand we still have active volcanic action in adja- 

 cent regions, and are not, therefore, surprised at the high temperatures. 

 On the other hand, where we have modern volcanic aciion we may not 

 have very high temperatures (due perhaps to the springs not coming 

 from so great a depth as in other cases). Thus, the hottest spring in 

 Europe, which is connected with volcanic action, according to Professor 

 Forbes,* is at the baths of Nero, near Naples, where the temperature 

 is 1820.2 F. In Iceland, in New Zealand, and in the Yellowstone Na- 

 tional Park, temperatures above the boiling point have been obtained. 



The hottest spring in Europe outside of the area of modern volcanic 

 activity, according to M. Arago, is that of Chaudesaigues in Auvergne,t 

 with a temperature of 176 op. That the mere presence of volcanic rocks, 

 whether ancient or modern, is not sufficient to produce hot springs is 

 well shown in our Eocky Mountain region, for we have large areas, 

 notably in Southern Arizona and California, Washington and Idaho 

 Territories, and in Oregon, where there are no hot springs. Perhaps 

 the explanation may be found in the fact that the rocks are mainly flows, 

 and the mass has so cooled that any thermal springs formerly existing 

 have become extinct. In many portions of the West the remains of 



* Phil. Trans., t. ii, p. 603, for 1826. 



t Annuaire du Bureau des Loagitudes, 1836. 



