484 



SURGEONS KEPORTS — CALIFORNIA — NORTHERN DISTRICT. 



Thermometer. — The thermometer, like the barometer, reveals some characteristics of a tropi- 

 cal, rather thau of the temperate climate to which, geographically, this district appertains. 



The mean monthly and annual temperature as seen in the accompanying tables are calculated, 

 like those of the barometer, from the daily observations made at 7 a. m., 2 p. m., and 9 p. m. 



The minimum temperature, as seen from the curve projected in the chart of hourly observa- 

 tions, occurs between 4 and 5 a. m., and the maximum about 3 p. m. Consequently the mean 

 deduced from the latter is generally minus that of the former. The following table is to be applied 

 in order to obtain the absolute mean. 



Thermometer. 



Dates. 1857. 



January 22... 

 Febrnary 23.. 



March 23 



April 29 



May 22 



June 22 



July22 



August 28. ... 

 September 23. 

 October 21 ... 

 November 27 . 

 December 23 . . 



Daily mean. 



48.00 

 54.00 

 52. 00 

 62.66 

 63.66 

 70,66 

 77.00 

 66.33 

 64.00 

 59.00 

 52.66 

 43.33 



Hourly moan. 



48.50 

 53.75 

 50.38 

 61.88 

 62.46 

 69.83 

 75. 23 

 65. 21 

 64.08 

 58.50 

 53.58 

 43.50 



Sum .. 

 Mean 



Diflerence. 



-f 0.50 



— 0.25 



— 1.62 



— 0.78 



— 1.20 



— 0.83 



— 1.77 



— 1. 12 

 + 0.08 



— 0.50 

 + 0.92 

 + 0.17 



9.74 

 0.81 



It will be seen in the table subjoined that the measures of critical intervals are so far from cor- 

 responding with the quantity obtained in all other localities, and which are generally so near as to 

 amount almost to a constant, that the two times of day at which the mean temperature occurs can 

 only be regarded as appro.ximative. January affords a solitary instance of the daily mean temper- 

 ature occurring after midnight, viz., 12 h. 30 m., p. m. 



Table of the hours of mean temperature and the ^'■critical inter vaV^ between those hours. 



Dates. 1857. 



January 22 . . . 

 Februaiv 23.. 



March 22 



April 29 



May 22 , 



June 22 



July 22 



August 28 



September 23. 



October 21 



November 27 . 

 December 23 . 



Daily mean. 



48.50 

 53.75 

 50.38 

 61.88 

 62. 46 

 69.83 

 75.63 

 65.21 

 64.08 

 58.50 

 53.58 

 43.50 



Morning mean. 



lib. 

 10 b. 



8 b. 



9h. 



7 b. 



7 h. 



8 b. 



7 h. 



8 b. 

 9h. 



10 h. 

 10 b. 



30 m. 

 45 m. 



41 m. 



53 m. 

 30 m. 

 33 m. 



54 m. 

 36 m. 



42 m. 

 38 m. 

 47 m. 

 45 m. 



Evening mean. 



Critical interval. 



12 b. 

 10 li. 



y b. 



9 b. 



8 b. 



8 b. 



8 b. 



8 b. 



9 b. 

 9 b. 



12 b. 

 9 b. 



30 m. 



15 m. 

 19 m. 



7 m. 



16 m. 

 6 m. 



41 ni. 

 47 m. 

 55 m. 

 15 m. 

 35 m. 

 30 m. 



Mean . 



13 h. 



11 b. 



12 b. 



11 b. 



12 b. 



12 b. 

 11 b. 



13 b. 

 lib. 

 11 b. 

 13 b. 

 10 h. 



30 m. 

 38 m. 

 14 m. 



46 m. 

 .33 m. 



47 m. 

 11 m. 

 13 m. 

 37 ni. 



48 m. 

 45 m. 



12 b. 20 m. 



One of the most striking features of the climate seen on the accompanying chart of diurnal 

 variations, is the great reduction of temperature after the hour of maximum observation. How- 

 ever high the wave of temperature towers up under the influence of a vertical sun and cloudless 

 sky, it sinks proportionately low during the night, renderin.i; it cool and chilly. 



The following table exhibits the successive hourly ranges daring one day of each month of the 

 year : 



