WIND TABI^ES. xliii 



TABLE 46. 



Table 46. Depth of water corresponding to the weight of snow (or rain) 

 collected in an 8-inch gage. 



The table gives the depth to hundredths of an inch, corresponding to 

 the weight of snow or rain collected in a gage having a circular collecting 

 mouth 8 inches in diameter — this being the standard size of gage used 

 throughout the United States. 



The argument is given in avoirdupois pounds, ounces and quarter 

 ounces in order that it shall be adapted to the customar}- graduation of 

 commercial scales. 

 Example : 



The weight of snow collected in an S-inch gage is 2 lbs. 2^ oz. To 

 find the corresponding depth of water. 



The table gives directly i.i8 inches. 



TABLE 47. 



TABLE 47. Rate of decrease of vapor pressure with altitude. 



From hj^grometric observations made at various mountain stations on 

 the Himalaj-as, Mount Ararat, Teneriffe, the Alps, and also in balloon 

 ascensions. Dr. J. Hann {Zeitschrift fi'ir Meteorologie, vol. ix, 1874, p. 193-200) 

 has deduced the following empirical formula showing the average relation 

 between the vapor pressure f at a lower station and/ the vapor pressure at 

 an altitude h metres above it : 



/ -^ 



-^ = 10 6517- 



Jo 



This is of course an average relation for all times and places from which 

 the actual rate of decrease of vapor pressure in an}- individual case may 

 widely differ. 



Table 47 gives the values of the ratio ^ for values of h from 200 to 



Jo 



6000 metres. An additional column gives the equivalent values of h in feet. 



WIND TABLES. 



CALCULATION OF THE MEAN DIRECTION OF THE WIND BY LAMBERT'S 



FORMULA. 



lyambert's formula for the eight principal points of the compass is 

 E- W + (NE ^ SE -NW-SW) cos ^^° 



fin ct — -^ ■ ■ — ■ • 



N-S-\- {NE + NW- SE-S W) cos 45" 



a is the angle of the resultant wind direction with th% meridian. 



E, NE, N, etc., represent the wind movement from the corresponding 

 directions East, Northeast, North, etc. In practice instead of taking the total 

 wind movement, it is often considered sufficient to take as proportional 



