THE BAROMETER. 277 
Greatest daily range of temperature, 23 (30th). 
Least daily range of temperature, to (28th). 
Mean of maximum temperature, 78.4. 
Mean of minimum temperature, 61.8. 
Mean daily range of temperature, 16.6. 
Total rainfall or melted snow, 9.31 inches. 
Prevailing winds, southwest. 
Maximum velocity and direction, 50, south (1:15 a. m., 5th). 
Total movement of wind, 6,077 miles. 
Number of cloudy days on which rain fell, 9. 
Number of cloudy days on which no rain fell, o. 
Number of days on which rain or snow fell, 16. 
Rain or snow preceded by wind from southwest, 4 times. 
Rain or snow preceded by wind from south, 3 times. 
Rain or snow preceded bv wind from southeast, 3 times. 
Rain or snow preceded by wind from east, north and west, each once. 
Clear days, 0; fair, 21; cloudy, 9. 
Mean of barometer, corrected for temperature only, 28.938. 
THE BAROMETER. 
During the past month, the steadiness of the barometer was most noticeable. 
From the 16th to the 21st it was almost motionless with the least possible wind 
during that time. Even during the excessive rainfall of the 14th the barometer 
was of nearly normal height, and stationary. But then it is to be noticed that 
the wind was moderate in force and amount, while during the heavy wind storms 
of the fifth and sixth the variation was very great. 
The barometer is a most valuable instrument, but the usual legends affixed, 
of wet and dry, and changeable, are mostly hypothetical. It merely measures the 
pressure of the air at the moment of reading. These, compared with other 
readings, may give data for deducing probable changes, but alone they are ex- 
ceedingly vague. Consider that the amount of rain which fell in this vicinity upon 
the 14th would have made a solid block of ice with a square base the size of the 
park, three feet thick for every mile. What sustained this tremendous weight 
before the storm it is difficult to conceive. If the air rushed in to fill the space 
before occupied by vapor tension, destructive winds might have been expected. 
If the elastic force of the vapor exactly compensated for diminished pressure 
before, while the solid air compensated afterward, this implies two elements © 
whose action upon the barometer are so similar as to make the real cause undis- 
coverable. There is certainly in most cases a great loss of power which, by cal- 
culation, should be expended. 
For example. The force required to sustain a column of mercury 27.97 
inches in height is 14.73 pounds. This is about half a pound per square inch of 
mercury. If during twenty-four hours the barometer should change an inch, 
this would give a total variation in pressure equal to about seventy-two pounds 
