THE SMITHSONIAN INSTITUTION. 263 



Meteorological Observations at Sacrame?Uo, California, lat. 38° 34' 42" 

 north, long. 121° 40' 05". 



BY F. W. HATCH, M. D. 



The observations with the thermometer and barometer, and record 

 of the winds, embrace a period of ten months, from June, 1854; and 

 those of the psychrometer, the period embraced between August, 1854, 

 and March, 1855, inclusive. The means of the thermometer are calcu- 

 lated from four daily observations, viz : at sunrise, (for which the mini- 

 mum is used, at noon,) at sunset, and 10 p. m. ; those of the barometer, 

 from three daily readings, at sunrise, noon, and 10 p. m; and the same 

 number for the psychrometer, but at different hours, viz : at or near sun- 

 rise, 3 p. M., and 10 p. m. The course of the wind is given four times 

 daily, corresponding with the observation^ of the thermometer, and will 

 serve to show the influence of the wind, both upon the elevation of the 

 barometer and the humidity of the atmosphere. A long and patient 

 examination and system of comparison, upon this subject, has convinced 

 me of the almost perfect uniformity of a high barometer and a northerly 

 wind, (north or northwest,) and the reverse condition with a south or 

 southeast wind. There are some exceptions to this rule, and in our 

 northwest gales the barometer often lalls low ; but what I have stated 

 is the ordinary course under ordinary conditions. The source of these 

 vvinds in the mountains of Oregon, and of the others (south, southeast, 

 and southwest) from the Pacific, will, moreover, account for their 

 respective influence upon the humidity of the atmosphere. 



Not less evident is the relation of the winds to temperature, espe- 

 cially in the summer months. It is common, at this season, for the 

 wind, after sunrise, to change to a northerly direction, and to continue 

 in this quarter for a greater or less length of time, varying from a lew 

 hours to a period of the day as late as 3 or 4 p. m. In their passage 

 over the burning plains of the interior, and by contact with the heated 

 air, they have acquired, before they reach here, an elevated tempera- 

 ture, and are dry and occasionally hot. This state of things is, how- 

 ever, mostly succeeded by a dehghtful breeze from the ocean in the 

 afternoon, when both the temperature and the humidity of the atmo- 

 sphere undergo a rapid transition. These facts would be more clearly 

 denoted by an examination of the daily record, and especially by a 

 separate observation in the forenoon, than by the means which I send, 

 inasmuch as the northerly wind of the morning is frequently unnoticed 

 in my regular tables, from the fact of its prevalence only between the 

 hours of sunrise and noon. The above is a correct view of the ordinary 

 course of the wind in the summer season. In the winter, on the con- 

 trary, the north wind prevails more, and comes to us in all its original 

 freshness and coolness. 



