Ixxiv INTRODUCTION. 



The argument is given in hundredths of a pound from O.oi pound to 

 0.99 pound. When the weight of the collected snow or rain is one pound or 

 more, the depth corresponding to even pounds may be obtained from the 

 equivalent of one pound given in the heading of the table. 



Example : 



The weight of the snow collected in a gage having a circular collecting 

 mouth 8 inches in diameter is 3.48 pounds. Find the correspond- 

 ing depth of water. 

 A v/eight of 3 lbs. corresponds to a depth of water of 



0-5507 X 3. equals 1.65 in. 



A weight of 0.48 \hs. corresponds to a depth of water of 0.26 



A " '" 3.48 " " " " " T^i in 



Table 89. Quantity of rainjall corresponding to given depths. table 89. 



This table gives for different depths of rainfall in inches over an acre 

 the total quantity of water expressed in cubic inches, cubic feet, gallons, 

 and tons. (See Henry, A. J. "Quantity of Rainfall corresponding to Given 

 Depths." Monthly Weather Review, 1898, 26: 408-09.) 



GEODETICAL TABLES. 



Table 90. Value of apparent gravity on the earth at sea level.'^ table 90. 



The value of apparent gravity on the earth at sea level is given for 

 every twenty minutes of latitude from 5° to 86°, and for degree intervals 

 near the equator and the poles. It is computed to 0.001 dyne from the equa- 

 tion ^ 



g<i, = 978-039 (i + 0.005294 sin- 4> — 0.000007 sin^ 2 4>) 



= 980.621 (l — 0.002640 cos 2 ^ + 0.000007 cos- 2 </)) 



in which g^ is the value of the gravity at latitude <^. 



The second form of the equation is the more convenient for the com- 

 putation. 



TABLE 91. 



Table 91. Relative acceleration of gravity at sea level at different latitudes. 



The formula adopted for the variation with latitude of apparent gravity 

 at sea level is that of the U.S. Coast and Geodetic Survey, given above. 



gi) 



The table gives the values of the ratio — _ to six decimals for every 10' 



of latitude from the equator to the pole. 



^ Gravity is here considered in terms of force (expressed in dynes) that is exerted on 

 a mass of one gram rather than its numerical equivalent, acceleration (expressed in cen- 

 timeters and seconds), for which there is no convenient expression. 



2 See Bowie, William, Investigations oj Gravity and Isostasy. U.S. Coast and Geodetic 

 Survey, Special Publication No. 40, 191 7, page 13^. 



