.64> 



The above formulas applied to the calculation of a ship's way. 



N- 

 D 



n 



o;+ w 

 0,4 w N. 



0,4 W= 



Thus the wind 30, and the distance 70 miles, then the 

 uumber of hours requisite to traverse that distance will be 

 5,8 for 30X0,4=12,0 and 12)70=5,8 hours. 



Again 0,4 AV. being 12, and the hours, 5,8, being given, 

 the distance 70 miles, we have 5,8xl2=6ii,6. by the second 



formula. 



And, lastly, the number of hours=5,8, and space in 

 miles=70 being given, we have 0,4 of the velocity of the 

 wind=?,i=12; and dividing this by 0,4, we have the rate 

 per hour of its course in the lower atmosphere. 



EXPLANATION OF THE DRAWING. 



Fig. 1. The anemometer, with a vane or weather cock 

 placed on the top, to shew the direction of the light- 

 er winds, Avhich could not be known by the anemo- 

 meter, on account of the weight of the necessary ap- 

 pendages annexed to it. This is raised of a sufficient 



height 



