xlvi INTRODUCTION. 



Table 55. Co7iversion of inetres per second into kilometres per hour. 



The argument is given for every tenth of a metre per second up to 60 

 metres per second, and the tabular values are given to one decimal. 



Table 56. Conversion of kilometres per hour into metres per second. 



The argument is given for every unit up to 200, and the tabular values 

 are given to two decimals. 



Table 57. Beanfort wind scale and its conversio?i into velocity. 



The personal observation of the estimated force of the wind on an 

 arbitrar}' scale is a method that belongs to the simplest meteorological 

 records and is widely practiced. Although anemometers are used at meteor- 

 ological observatories, the majority of observers are still dependent upon 

 estimates based largely upon their own judgment, and so reliable can such 

 estimates be made that for many purposes they abundantly answer the 

 needs of meteorology as well as of climatology. 



A great variety of such arbitrary scales have been adopted by different 

 observers, but the one that has come into the most general use and received 

 the greatest definiteness of application is the duodecimal scale introduced 

 into the British navy by Admiral Beaufort about 1800. 



The definitions of the successive grades of the Beaufort scale were 

 made in terms of the effect of the wind on the sails of a full-rigged ship, so 

 that navigators of all nations have generally acquired a very uniform and 

 definite idea of their meaning and a very considerable expertness in the use 

 of the scale. The Table gives the designations of the 12 grades together 

 with several conversions of the scale into wind velocities as made by 

 different meteorologists. A committee appointed by the Royal Meteoro- 

 logical Society to establish a conversion of the Beaufort scale into wind 

 velocity made a preliminary report {Quart. fo7irnal Roy. Meteorological Soc, 

 vol. 13, 1887), but did not consider their work sufficiently complete to present 

 a definite conversion table. 



GEODETIC AL TABI.ES. 



Table 58. Relative acceleration of gravity at sea-level at differe^it latitudes. 



The formula adopted for the variation of gravity with latitude is that of 

 Prof. Harkness* 



S^ =<^46 (i —0.002662 cos 2(}>) 



in which g^ is the acceleration of the gravity at latitude <j>, and g^^ the 

 acceleration at latitude 45.° 



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



A 46 



of latitude from the equator to the pole. 



* Wm. Harkness : The solar parallax and its related constants. Washington, 1891. 



