486 



surgeons' KEPORTS — CALIFORNIA — NORTHERN DISTRICT. 



miuimum of the latter, 41° 50'. It will be uoticed that iu our divisions of the seasons we Lave, 

 in accordance with the phenomena observed, defined February as the first of the spring mouths, 

 and appropriated five months to summer and only two to autumn and two to winter. Indeed, the 

 seasons are of so short duration that the tropical division into the wet and dry seasons would, 

 perhaps, be more appropriate. 



The whole jieriod of sensible winter is far from being a complete season of suspension of veg- 

 etation. Many forms of vegetation are active the whole period. 



The Jowest mean daily temperature of the winter season is seldom below 40°, although the 

 theimometer has been known to fall as low as 33° as late as the middle of February. The budding 

 process is evident during the first days of February. Usually the spring is well advanced iu 

 March. 



The greatest vicissitudes of temperature occur iu the summer season, autumn being similar to 

 spring. The first frosts occur about the middle of i!fovember. The decline to winter is gradual 

 antil the latter part of December ; ice is found during the last days of this month and January. 

 It seldom remains uuthawed for twenty-four consecutive hours. As a physical constant, it is a 

 matter of some difficulty to place within 5° of different latitudes isothermal lines for the season. 

 That of 60° for the spring, designed for the United States Army Meteorologic;il Eegister, which 

 connects Sacramento with Beaufort, N. C, on the Atlantic coast, and San Diego on the Pacific 

 coast, curves 5° 52' latitude to the south on arriving at the latter point. 



A corresponding divergence to the north occurs in winter. The isochimenal line of 45° wliich 

 is common to Beaufort, N. C, and Sacramento, describes a northerly curve of 8° 03' latitude before 

 reaching the Pacific at Port Orfonl, Oregon, latitude 42° 44', the mean annual temperature of which 

 place is only 53° OC. 



The isothermal' of 70° starting from latitude 40° on the Atlantic coast comes out on the Pacific 

 coast on parallel 30°. The great curvature to the south on the Pacific coast during spring and 

 summer demonstrates one of the peculiarities of the distribution of heat iu this region ; for the 

 mean of the three months of spring the temperature which predominates on the line of coast 

 westward of the Coast range of mountains is striliingly uniform, and shows but little, if any, 

 advance on that of winter. Indeed, the same may be said of the summer mouths. For some 

 hundreds of miles on the 40th parallel there is very little diflerence in the sea-temperature for the 

 entire year, and the cold of the Pacific extends, according to the showing of Blodget, from the 50th 

 to the 30th parallels. Thus, while the extreme summer heat is common to all the valleys, the 

 meau summer temperature of San Francisco and much of the coast north is only 00°. 



Tabic of greatest monthli/ vicissitudes of temperature, as obtained from two successive daily means. Cal- 

 culated for the meteorological seasotis of 1856 and 1857. 



Spring 



Sururaer. 



