94 



RESOURCES OF CALIFORNIA. 



68. Sunrise and Noon. The followiDg table, showing 

 the mean temperatures at sunrise and noon, was prepared by 

 Dr. H. Gibbons. 



The mean of sunrise rises regularly from January to Sep- 

 tember, but that of noon higher in June than in July and 

 August. The strong winds called in from the ocean to supply 

 the place of the air heated in the Sacramento-San Joaquin 

 basin, reduce the temperature of midsummer in San Francisco. 



69. Cold Days. The number of cold nights, those in 

 which the thermometer fell, at San Francisco, to 32, num- 

 bered seventy-four in the twenty years ending June 30th, 1872, 

 (according to Thomas Tennent's self-registering thermometer) 

 less than four to the year on an average. Of these seventy- 

 four cold days, twenty-four occurred in December, thirty-three 

 in January, eleven in February, four in March, and one each 

 in April and May. In the winters of 1852-53, 1864-65, 

 1866-67, 1868-69, and 1871-72, or five out of twenty winters, 

 not one cold day occurred. 



The seasons of 1854-55, 1859-60, .1860-61, 1863-64, and 

 1865-66, had each one cold day. 



The seasons of 1853-54, 1862-63, and 1869-70, had each 

 three cold days. 



