174 Headden — Silicic Acid in Mountain Str earns. 



have a common source, the melting snows on the peaks of the 

 Sangre de Cristo range on the east and on those of the San Juan 

 country on the west. The percentage of silicic acid in the 

 total solids, however, is as great as that in the residues obtained 

 from any of the geysers or other hot springs in the world. 

 The highest percentages that I have found for the -latter are : 

 for the Great Geyser of Iceland 42 per cent, calculated of 

 course on the total mineral matter held in sohition ; for the 

 Coral Springs in the Yellowstone National Park 32 per cent ; 

 for the Hot Spring, Garland, Arkansas, 23 per cent ; for the 

 White Terrace Geyser, JSTew Zealand, 22 per cent ; and for the 

 Calistoga Spring in California, 18' per cent. These examples 

 suffice to show the relative' richness of the Rio Grande del 

 Norte water and that of the springs and artesian wells of the 

 San Luis Yalley in silicic acid. 



It is perfectly plain that the absolute amount of silica carried 

 by the waters is not given by the statement of the percentage 

 of this substance in the total solids, but will depend upon this 

 latter, or the total amount of mineral matter held in solution. 

 In this respect, too, some of the spring and well waters carry 

 more significant quantities than one would expect."^ 



The Great Geyser of Iceland carries 86-1 ; the Coral Spring, 

 Yellowstone National Park, 133*7 ; White Terrace Geyser, 

 New Zealand, 185*5 ; and the Hot Spring, Arkansas, 5*0 grains 

 in each imperial gallon. The Rio Grande del Norte at Del 

 Norte carried 6*2; Dexter's Spring 13*7; Mclntyre's Spring 

 12*8; McNieland's Well 17*4; the Bucher Well 15*8; and 

 Spriesterbach's Well 28 grains. 



I considered the high percentages of silica in the total solids 

 of these waters as anomalous until a study of the waters of the 

 Cache a la Poudre and some neighboring streams led me to 

 change my view and to consider it as normal in the case of such 

 waters, and to attribute the absence of silicic acid from ordinary 

 waters to the character of the drainage area, the character of 

 the rocks through which the waters pass before they rise as 

 springs or artesian waters, and to changes suffered during the 

 course of their flow. 



The following analyses were made of residues obtained by 

 evaporating the samples to dryness ; both copper and porcelain 

 vessels were used without appreciable difference in the results. 

 The residues were dried at temperatures varying from 180° to 

 200° C. The ignition is put in brackets to designate that it is 



* I have reduced my data to the common basis of grains to the imperial 

 gallon because my own results have been calculated on this basis, and fur- 

 ther because grains per imperial gallon are easily converted into parts per 

 thousand or million according as one may prefer. 



