IfjO GKOLOGICAL HISTORY OF THE YELLOWSTONE PARK. 



may possess in alleviating' the ills of mankind. Nothiug but an 

 extended experience under proper medical supervision can determine. 

 I may say that no hot si)riuys with which I am acquainted prove so 

 delightful for bathing purposes and so agreeable in their action upon 

 the skin. 



Changes modifying the surface features of the park in recent times 

 are mainly those brought about by the tilling ui> with detrital material 

 from the mountains, the valleys and depressions worn out by glacial ice, 

 and those produced by the prevailing climatic conditions. Between the 

 park country and what is known as the arid regions of the West there 

 is the greatest possible contrast. Across the park plateau and the 

 Absaroka range the country presents a continuous mountain mass 

 75 miles in width, with an average elevation unsurpassed by any area 

 of equal extent in the northern Eocky Mountains. It is exceptionally 

 situated to collect the moisture-laden clouds, which coming from the 

 southwest precipitate immense quantities of snow and rain upon the 

 cooled table-land and neighboring mountains. The climate in many 

 respects is quite unlike that found in the adjacent country, as is 

 shown by the meteorological records, the amount of snow and rainlall 

 being higher, and the mean annual temperature lower. Eain storms 

 occur frequently throughout the summer, while snow is quite likely to 

 fall any time between September and May. Protected by the forests 

 the deep snows of winter lie upon the plateau well into mid-summer, 

 while at still higher altitudes, in sheltered places, it remains throughout 

 the year. By its topographical structure the park is designed by 

 nature as a reservoir for receiving, storing, and distril)uting an excep- 

 tional water supply, unexcelled by any area near the head-waters of the 

 great continental rivers. The Continental Divide, separating the 

 waters of the Atlantic from those of the Pacific, crosses the park 

 plateau from southeast to northwest. On both sides of this divide lie 

 several large bodies of water which form so marked a future in the 

 scenery of the plateau that the region has been designated the lake 

 country of the park. Yellowstone Lake, the largest lake in North 

 America at this altitude (7,740 feet) and one of the largest in the world 

 at so high an elevation above sea-level, presents a superficial area of 

 139 square miles, and a shore-line of nearly 100 miles. From measure- 

 ments made near the outlet of the lake in September, 188(5, tiie driest 

 period of the year, the discharge was found to be 1,525 cubic feet per~ 

 second, or about 34,000,000 imperial gallons per hour. 



At the same time all the priucij^al lakes and streams in the park 

 were carefully gauged. Dr. William Ilallock, who undertook this work, 

 estimated that the amount of water running into the park and leaving 

 it by the Yellowstone, (xallatin, Madison, Snake, and Falls rivers, the 

 five main drainage channels, would be equivalent to a stream 5 feet 

 deep, 190 feet wide, with a current of 3 miles per hour, and that over 

 an area of 4,000 square miles the minimum discharge was equal to 1 



