RECORD AND DISCUSSION OF ATMOSPHERIC PRESSURE. HI 



ing, each fall of snow. If snow fell for less than three consecutive hours, I have 

 taken no notice of it in this investigation. The mean result from 563 hours of 

 comparison, gave only a difference of O.OOG inch, by which quantity the barometer 

 is lower during the fall of snow than otherwise. 



Variability of Atmospheric Pressure icith the Direction of the Wind. The connec 

 tion of the atmospheric weight with the direction of the wind requires, in order to 

 find its average effect, a great number of observations, particularly on account of 

 the irregular oscillations of the barometer in the winter months. The following 

 results are derived from a comparison of the barometric readings at the hours 6 

 A. M., noon, 6 P. M., and midnight, for each day, with the respective mean monthly 

 reading during IT months of observations. These difference were then arranged 

 according to the directions of the wind. The result is as follows (+ indicating 



I above 1 the mean) :- 

 (. below J 



Magnetic direction. Inch. 



N 0.022 



N.I ]. . . . + 0.072| On account of the comparatively small number of observations for 



E. .... 0.100J these directions, they may lie combined : E. N. E. 0.044 in. 

 S. E. . . 0.000 



S. . . +0.038 



S. W. . . . +0.045 



W 0.031 



N. W. . . . 0.031 



From 1050 comparisons of calms and barometric readings, the latter were found 0.005 inch above 

 their mean value. 



It is only during S. and S. W. (magnetic) winds that the barometer rises above 

 the mean value; during all other winds it is depressed. 



Relation of the AtmospJicric Pressure to each Wind and to the Temperature of tltc 

 same. To show this dependence, it is best to put the relation of the atmospheric 

 pressure, as well as that of the temperature, to the winds, in an analytical form. 

 In my discussion of the observed temperatures at Van Kensselaer Harbor, a table 

 was made out showing the dependence of the temperature on the direction of the 

 wind. If we deduct the mean elevation of temperature by the winds from each 

 separately, we obtain the following table of the effect of each wind on the tem 

 perature (+ indicating an &amp;lt; &amp;gt; of temperature) : 



(. depression ) 



Magnetic direction. Magnetic direction. 



N. 



s 



N. E 0.0 S. W +0.4 



E 0.1 



S. E. . . +0.9 



W +0.1 



N. W. . 1.4 



Counting from the north (or belonging to a (magnetic) north wind) round by 

 E. to 300, we obtain, by using Bessel s formula, 



T= + l.026-m (0 + 280); 

 or, for the true directions, 



r= +l.02*m (0 + 34); 



and similarly, from the barometric relation to the winds, 



J5= +0.018 in. sin (0 + 354). 



