159 



Much ci'edit is due Miss Sabra Snell, who kindly allowed the 

 writer the use of the valuable records in her charge, which greatly 

 aided him in arriving at the results herewith submitted. The data 

 mostly reviewed are those relating to atmospheric pressure, tem- 

 perature and precipitation in the form of rain and snow. Accom- 

 panying these results will be found a chart upon which curves are 

 traced, showing the fluctuations of the mean yearly barometric 

 pressure, mean annual temperature, mean temperatures of the 

 summer and winter mouths, and the rain and snow fall for the last 

 fifty-seven and tifty-two years respectively. 



Atmospheric Pressure. 



From what has been observed and recorded, we deem it safe to 

 say that the mean barometric pressure at Amherst (reduced) is 

 seldom if ever greater than 29.81 inches, or less than 29. G6, the 

 difference being .15 of an inch. It is found that during fifty-six 

 years the mean barometer has fallen below 29.70 only nine times, 

 while it has reached 29.70, or above that point, forty-seven times. 



It is also noticed that the first mean recorded was 29.68 ; fifteen 

 years elapsed before the mean again fell below 29.70 ; three years 

 intervened, when the mean was again below 29.70 ; two years 

 later the same occurred, making the cycle of five years complete; 

 two periods of five years passed, and at the end of each the mean 

 fell below 29.70; then came a break of three years, after which 

 another period of five years and a minimum below 29.70, the latter 

 always occurring on the fifth year or the one following. Fourteen 

 years have elapsed since the last minimum below 29.70 was 

 recorded. Thus from the facts above noted it would seem that 

 the minimum pressures, with few exceptions, occur in cycles, and 

 that the number of years in these cycles is some multiple, or 

 very near some multiple, of five. Basing the value of future 

 expectations on deductions already made, we find the probability 

 that the mean pressure in inches for each of the next fifty-six 

 years will be — 



At least as high as 29.70 



At least as high as 20.72 



At least as high as 29.74 



At least as high as 29 ;76 



At least as high as 29.77 



At least as high as 29.78 

 Above . . .29.78 



Tem2:>erature. 

 In 1830 the mean temperature was 52.70°, and fifty-two years 

 after the mean was 50.88°. The number of years between these 



