70 THE MOUNTAINS OF COLORADO. 
then, the formation of the mineral veins of this region may be 
referred to two distinct epochs. 
The veins of Colorado, thus far mined, belong to the older class. 
The gold-bearing veins, unlike those of California, contain in 
their gangues, copper and iron pyrites, blende and galena, and wg 
intimately is the gold connected with these sulphurets, that great 
loss is incurred in its extraction. ; 
The veins of silver have, also, their associations of base sul- 
phurets, and the silver itself appears under the forms of sulphu- 
sites of gold mining, while Georgetown is the focus of silver mining. 
The annual product in the precious metals as estimated by Clar- 
ence Kingis about three million, two hundred and fifty thousand 
dollars. As constituting a part of the volcanic phenomena, may* 
mentioned the frequent occurrence of hot springs throughout the 
whole atea oceupied by this mountain system. In Colorado, te F 
most noted are those of Middle Park and Idaho. ‘The former A 
not readily accessible, and I am not aware that their waters me 
been subjected to analysis. The latter are now resorted to for 
their remedial virtues in cases of rheumatism, paralysis, and ie 
taneous affections. These springs issue from the left bank of 
Soda Creek, and are three in number. The flow is not oo 
being about ten gallons a minute. The temperature is 109° # 
An analysis of the water by Mr. J. G. Pohle of New York, gave 
one hundred and seven grains of solid matter to the gallon, e 
up of the following ingredients : 
Carbonate of Seda s a oer eR Ea ee ee pe ' 
Carbonate of piao; 6 iaoi aa vig ee ae Sa 9. an 
Carbonate ʻof Magnesia, . . . n EPEA E a > 2 
Carbonate of Iron, ý 3 5 y : 29.36 
Sulphate of Soda, e a a r N E et aake BR 
Sulphate of Magnesia, š ý > š k ft Os te . 3.44 
Sulphate of Lime, Š x 3 č ` ‘ PoE E . d 416 Pie 
Chloride of Sodium, . hee 4 í oe a n A 
Chloride of Calci d Magnesium, of each a trace, 4.08 
Silicate of Soda, ‘ $ n < t fi š ; : 
107.08 
Cimate.—One of the most striking peculiarities of these 
tains is the absence of a perpetual line of congelation. Mr. m m é 
in his little work on this region, calls special attention to tea 
nificant fact, and points out the diversities between these F 
tains and those of Switzerland ; and what I propose to state 
