Temperature of the Year. 



37 



ive hours. The record was, however, discontinued every week 

 from Saturday, 7, P. M. to Sunday, 7, P. M. During a part of 

 the long autumnal vacation, when few students remained in town, 

 the record was made but once in two or three hours by night, 

 and the intermediate numbers were supplied by interpolation. 

 Throughout the year, I almost every day attended personally to 

 the location of the thermometer, that it might have such an ex- 

 posure as to indicate correctly the temperature of the air. The 

 entire number of observations was seven thousand five hundred 

 and twelve, distributed equally through the year, or about six 

 hundred and twenty-six each month. The following table ex- 

 hibits the mean temperature of the several months, and of the 

 year, according to Fahrenheit's thermometer. 



I Jan. 

 22°94 



Feb. I Mar. 

 28?57l34°81 



April. 



,4S°54 



May. 

 56?92 



June. 

 6L60 



July. 



o, 

 71,61 



67.44 



Sept. 

 59?80 



Oct. 

 50?46 



Nov. 

 34?80 



Dec. 



29?28 



Year. 

 47°23 



Besides the daily, monthly, and annual averages, I also obtained 

 the averages of the corresponding hours for every month, and 

 for the year. Thus, in January, the mean temperature at 1, A. 

 M., was 19°.04; at 2, A. M., 18°.70, &c. All these results are 

 presented at once to the eye in the plate, in which the mean diur- 

 nal changes of each month are represented by a curve, whose 

 coordinates show respectively the hour of the day and the degree 

 of temperature. The horizontal ordinates indicate the hours ac- 

 cording to the marking at the top and bottom ; the vertical, the 

 temperature, as expressed on the left ; on the right are marked 

 the months, to which the several curves belong. 



By tracing the curve for January, it will be seen, that the mean 

 temperature at 1, A. M. was above 19°, and slowly descended 

 till 7, A. M., whence it rose rapidly till 2, P. M., and from 2 till 

 midnight descended again, rapidly between 4 and 6, the rest of 

 the time slowly. It appears, therefore, that the maximum heat 

 of this mean January day occurred about 2, P. M., and the min- 

 imum about 7, A. M., the range being near 12^°. The curves 

 for the other months have the same general form. The maxi- 

 mum is always near 2, P. M. ; but the minimum, which com- 

 monly takes place near sun-rise, varies from 4 to 8, A. M., accord- 

 ing to the season. The heavy curve, commencing near 43° on 

 the left, and marked " year " on the right, exhibits the mean of 

 all the other curves; and hence represents the thermometrical 



