\H0MET1UCAL AND METEOKOLOC.K'AL OBSERVATIONS. 



month of different vear 



s. We frequently find 



winter as in summer. 





The most abnormg 



il of our diagrama is ag; 



with little changes, from 

 amplitude 0.022 inches. 



the pressure is high from before neon till 7 p. m. The mean force is 0.540 inches, the 

 amplitude 0.074 inches. 



In August, the minimum takes place at 5 a. m., the maximum lasts (rem 2 to 6 p. 

 m., or we might even say from 11 to 6; the mean force is 0.625 inches, and the ampli- 

 tude 0.084 inches. 



In September the minimum lasts from 4 to (> a. in., the maximum from 5 to 6 p. 

 m., but the pressure is high from 11 a. m. to G p. m. The mean force is 0.507 inches, 

 and the amplitude 0.063. 



glance at the diagrams illustrating the observations at the Girard College, Philadelphia, 

 as published by order of Congress, shows that the pressure varies much in the same 



l and two minima as well in 



■ Woodruff Valley at the end 

 of May, No. VIII. It exhibits exactly the reverse of the Philadelphia variations. The 

 maximum then took place at sunrise, and the minimum in the afternoon. The cause 

 of this peculiarity will be readily understood. At sunrise the quantity of vapor was 

 not much below its maximum, and the relative humidity so decidedly at its maximum 

 that the great depression of the temperature could not counteract those combined in- 

 fluences. The relative humidity then declined so rapidly that its influence gained 

 upon that of the increasing temperature, and the force of the vapor gradually declined. 

 By noon the temperature had nearly reached its maximum, and therefore the still de- 

 creasing quantity of vapor and relative humidity caused a rapid diminution of the pres- 

 sure, which lasted till near sunset, when it had attained the exceedingly low figures of 

 0.038 inches. The rapidly increasing relative humidity then raised it, notwithstanding 

 the continued decrease of the temperature, till it reached the maximum at sunrise. The 

 mean force was 0.093, only the fifth part of what it is at that season at Philadelphia, 

 and the amplitude reached the large figure of 0.091 inches. 



At Camp Floyd in September, as illustrated by diagram No. VI, the decrease of 

 the relative humidity was slower in the morning; therefore the influence of the tem- 

 perature gained upon it, and a divided maximum took place at 9 a. m., upon which the 

 decrease of the force became very rapid until it reached its minimum, about 4 p. m.; 

 then, with the increasing relative humidity, it increased first faster then less till near 

 midnight, when the influence of the decreasing temperature became as strong as that 

 of the increasing relative humidity, and the force remained unchanged till sunrise. The 

 mean force was very low, only 0.103 inch, the amplitude 1.29 inches. 



The August curve at Camp Floyd is similar, but continues increasing, although 

 less during the night. It shows, however, a bend after sunset in consequence of the 



