Meteorological Observations. 127 



Mean temperature for the year, 54° 93', being, two and a half 

 degrees more than in the year 1829. 



Rain and snow, 37 ■^%% inches, being more than two inches less 

 than in the preceding year. 



Prevailing winds, from the S. S. W. and N. N. W. 



Heat the greatest in July, and least in January. 



We have had fifty-three fair days more than in the year 1829; 

 this will explain the diminution in the quantity of rain. The season, 

 after the 4th of July, having been an uncommonly dry one — crops of 

 Indian corn and potatoes suffering more from drought, than in any 

 preceding year, since 1804 : from the 4th of July to the 5th of Sep- 

 tember, there fell but two and a half inches of rain, while the heat 

 from the 5th of July to the last of August, ranged from 85° to 94°, 

 in the middle of the day, and the mean temperature for those two 

 months was above 75° night and day. The heat and drought ex- 

 tended nearly or quite all over the Mississippi valley -, while at the 

 same time excessive rains were falling on the borders of the Green 

 Mountains, and in the New England States. The spring months 

 were unusually fine : fruit trees were in blossom nearly twenty days 

 earlier than in 1829, and all the spring crops ripe two or three weeks 

 sooner. Professor Olmsted's theory of our climate is by far the 

 most plausible of any which I have seen, and his facts as to the prev- 

 alence of western winds over the United States, coincide with the 

 observations made at this place. The general current of the atmos- 

 phere is from the west, setting round to the eastern quarter from the 

 north, making a regular circuit in this manner, viz. — -South-west, 

 west, north-west, north, north-east, east, south-east and south j but 

 never in the opposite direction. This series has been often observed 

 in the vernal and autumnal months. The reader, in looking over 

 the barometrical register, will doubtless be surprized at its low range. 

 By comparing it with a table kept at Lexington, (Ky.) and one in 

 Athens, (Ohio) I find it is too low by about //o of an inch, proba- 

 bly from there being a little air in the top of the tube. But from all 

 the observations I have seen, there is a difference of nearly an inch 

 in the mean annual altitude of the mercury here, or that near the 

 Atlantic shore. I have kept a table of atmospheric variations for 

 three years, but have offered none for publication until now ; by 

 making the allowance above noted, it will vary but little from the true 

 state of the barometer in this part of the valley. 



