398 KEPORT UNITED STATES GEOLOGICAL SURVEY. 



SECTION IIL— FOEMATIONS AND DEPOSITS. 

 CHAPTER VIII. 



PHYSICAL FEATURES OF DEPOSITS. 



AMOUNT OF DEPOSITS. 



The amount of sediment deposited by thermal springs seems almost 

 incredible, especially in the case of calcareous tufa, which, as we have 

 seen, is more rapidly deposited than the siliceous sinter. In 1604, 

 Father Joseph de Acosta describes the springs of Huanvelica, Peru, as 

 depositing stones of Avhich houses are built.* In Hungary, also, where 

 enormous deposits of both travertine and siliceous sinter are found, 

 towns are built of it, and the same is true in Italy, where the deposits 

 at San Vignone are quarried for building purposes. 



Saint Peter's and all the principal buildings of Eomeare constructed 

 of Travertine or " Tiburstone." 



In Carlsbad the hot springs have deposited masses of pisolitic rock (Strudelstein) 

 which have filled u]} the whole bottom of the valley, and upon these deposits the town 

 itself is mainly built, t 



The deposits at the baths of San Vignone, Italy, have a thickness of 

 250 feet, and at San Fillipo, near Eome, entire strata of 328 feet thick- 

 ness are found. 



At Hamman Meskoutine, in Algiers, there are wall-like masses 4,921 

 feet long, 66 feet high, and from 33 to 49 feet in width. This is calca- 

 reous tufa. 



At Clermont, in Central France, according to Le Coq, there are six- 

 teen springs in four groups, and the deposit forms an aqueduct 300 feet 

 long and 16 feet wide. The whole ground in some parts of Tuscany is 

 coated with travertine, so that the ground sounds hollow beneath one's 

 feet. 



The deposits from the Bath spring, in England, if collected during 

 the last 2,000 years, would, according to Judd,| forma solid cone equal 

 in height to Monte Nuovo, in Italy. Professor Eamsay says that in 

 one year the solid matter brought up by this spring is enough to form a 

 column 9 feet in diameter and 1,440 feet high. In Virginia the springs 

 have a deposit 30 feet in thickness. At Hierapolis the deposit of car- 

 bonate of lime rises 100 feet above the plain and has a width of 600 feet, 

 and upon this the city stands. Back of this is another set of calcareous 

 hills in which the springs are found. This is like the deposit at the 

 Gardiner's Eiver springs in the Yellowstone Park. The deposits here 

 cover an area of about three square miles. The main mass is 200 feet 

 high and over 300 yards in width, and this is but a small portion of the 

 deposits, as a glance at the map of the Mammoth Hot Springs, in Chap- 

 ter I, Part I, will show. 



So far we have considered only the calcareous deposits. When we 



* The Natural and Moral History of the Indies, &g., London, 1604 ; printed in Lon- 

 don for the Hakluyt Society, 1880. 

 tJudd's Volcanoes, p. 184. 

 t Judd's Volcanoes, j). 219. 



