XXll 



BOTANY. 



The degree of dryness of the air is also shown by the results of a series 

 of careful measurements of the actual amount of evaporation taking place in 

 vessels of water exposed to the full influence of sun and wind. The portion 

 of these measurements made during fifteen days in June, fifteen days in July, 

 and fourteen days in August, 1868, give very closely approximating means, 

 and a general average daily evaporation of .5107 inches. Of this amount 

 .4019 inches, or very nearly four-fifths, were evaporated between 6.00 A. m. 

 and 6.00 p. m. The maximum evaporation for any hour observed was .0607 

 inches, and the largest amount recorded during any six hours is .3333 inches 

 between 10 A. m. and 4 p. m., as shown in the following readings for July 23d, 

 at Camp Ruby. 



Record of Evaporator; Camp Ruby, July 23, 1868. 



GrENERAL Chaeacter OF THE VEGETATION. The following statements 

 are based upon the results of field-work in Nevada in 1867 and 1868 and in 

 Utah in 1869. Entering Nevada from California, collection was commenced 

 on the 16th of July, 1867, in the valley of the Truckee Eiver by Mr. W. "W". 

 Bailey, botanist of the expedition, and was continued through the season but 

 confined wholly to the district between the Virginia and Pah-Ute Mountains. 

 The summer was already so far advanced that the earlier vegetation had dis- 



