454 SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 



may, iu like manner, easily compute the pressure s;, correspondiug to 

 the above given values of x and a. Computing the value of z, we get, 



V^ F2 yi Y2 



= O.G5— ; =1.0G — : =1.33 — : =1.51 — : 

 g i) 



y2 Y2 Y2 



= 1.G4— : =1.83—: =1.91-1-. 

 (J 9 9 



If we now institute a comparison between the computed and the 

 observed values of z, it becomes evident that the computed values stand 

 iu a constant ratio to the observed values, as would be the case if the 

 theory which has been advanced concerning atmospheric whirlwinds is 

 correct. If we therefore make the computed values of z equal to the 

 correspondiug observed pressures z, we get several equations, which 



may serve to determine the constant ( — ] , and thus we obtain, as a 



mean number: — = 9.7G Paris lines. If this mean value is substituted 

 9 



Y'i 

 iu the formula (1) for — , it is easy to compute the pressures which cor- 

 respond to the distances 

 x = 0; x = {i.lH; =0.2H; 0.3 if; 0.4 if ; = 0.5 E) = 0.75 H; = 1.0 II. 



These computed pressures are thus found to be : 

 -=0; =G.34; =10.35; =12.98; =14.74; =16.01; =17.8G; = 18.G4; 

 while the above observations gave 

 c = 0; = C.3; =10.4; = 13.2; = 15.0; = IG.l; = 17.5; = 18.3; Paris lines. 



So complete an agreement is therefore seen between the observed and 

 the computed pressures at every place in the hurricane that we may 

 draw the conclusion that the formula (4) is correct, and that the correct- 

 ness of the theory is confirmed by nature. But if the theory is correct, 

 and we therefore, for the hurricane now under consideration, have the 



pressure — = 9.7G Paris lines = 22.0 millimeters of mercury = 710 feet 



of air, it then further follows that the greatest velocity of the hurricane 

 was: V = 140 feet (47.C meters) per second, or something near to the 

 greatest hurrieane velocity of which we have any knowledge, which also 

 agrees with the violence with which the Antigua hurricane raged. 



We are now further able to determine the limits of the hurricane 

 proper, a term which is usually considered to apply to winds that have 

 velocity of 120 to 150 or more feet per second; for if in formula (I) we 

 make v = 120 feet, and F= 149 feet, we find the required distance 

 X = 0.53 H =12.7 miles. The hurricane proper began, therefore, at about 

 half past five o'clock at a distance of about fifteen miles from the axis, 

 and ceased at half past ten o'clock, or two and one half hours after the 



