384 PROCEEDINGS OF THE AMERICAN ACADEMY. 



In Alger's " Exterior Ballistics " I find the following passage : 



" Expressing the retardation caused by the resistance of the air in 



d 2 

 the form A —v n , in which d is the diameter of the projectile in inches, 



w its weight in pounds and v its velocity in f. s., Mayevski's equations ■ 

 are as follows : " 



"v between 790 f. s. and f. s., 



Hd ^ = - Al ^ log A 7 = 5.669... (-10). 



"The coefficient A depends on the shape of the projectile. In 

 Mayevski's calculations the ' ogival ' form [the shape of an ordinary 

 artillery ' shell '] is assumed, the ' ogival ' heads having two calibers 

 radius. A would be greater with hemispherical heads." 



Mayevski's formula is equivalent to 



Resistance (poundals) = — w-j- = Ad 2 X v 2 . 



Taking this formula for the case in which d is one inch, the diameter 

 of the bronze balls, and the velocity is 1 cm. per second, we get for the 

 " ogival " form, 



2 



Resistance (poundals) = A ~ 30.5 , 



(dynes) =A + 3(15 X (458 X 30.5) = 0.00069. 



This is about 45 per cent of the value, 0.00154, found above for /■ in 

 the case of spherical one inch balls. 



Jefferson Physical Laboratory, 

 Cambridge, Mass., 

 January, 1910. 



