63 



4. According to Lalande, in his Treatise on Navigation, 

 42 Roz. Jour. 221. tlie course of the trade winds is between 

 6 and 7 miles an hour. 



5. Mr. Brice, Philosophical Transactions, 1756, p. 226, 

 observed a storm, whose velocity Avas 63 miles per hour. 



6. A fair wind at sea, is that whose velocity amounts to 

 20 feet per second, or 13,63 miles per hour. Ibid. 



7. Bouguer found the velocity of winter storms to be 

 about 34 miles per hour, and in summer nearly 43. Ibid, 



The distance from Holyhead to the Pigeon-house is 70 

 miles; then supposing the wind to be direct, and its velocity 

 30 miles per hour, and if we suppose the packet-boat to 

 assume 0,4 of the velocity of the wind, it will arrive at the 

 Pigeon-house in 5,8 hours. 



Let W denote the velocity of wind in the open air, or 

 meeting no opposition; 

 D = the distance of the place towards which the 



wind tends; 

 N the number of hours it requires to traverse that 

 distance; 

 Then any two of these being known, the other may be found 

 by the following formulas. 



^ Thus if W=30, D=70 

 N=5 ( then N---ll=2,33 

 D=wN ? D=30X2,33=70 



A well sailing ship assumes i of the velocity of the wind^ 

 The best saiUng ship 0,4 of the wind's velocity^ 



The 



