SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 



46; 



from the southwest to southeast ; at the same time the barometer began 

 to rise. Five series of meteorological observations during this hurri- 

 cane are at hand. The observed values of the atmospheric pressure for 

 three of these are graphically presented in Fig. 3. 



FIG. 3. 



The most complete observations, corresponding to the curve through 

 the simple points (.), were made on the French steamship La Yille de St. 

 Nazaire, Captain d'Etroyat. The points enclosed in circles are entered 

 according to the observations on the ship Tyne, Captain Taylor. Both 

 these series of observations were instituted in the harbor of St. Thomas. 

 The curve designated by Caravelle is drawn according to the observa- 

 tions on the steamer of the same name, which was 4 or 5 miles north of 

 Porto Rico, at a distance of 54 nautical miles from St. Thomas. 



The whirlwind began at St. Thomas about 12.30 p. m. and ceased 

 about 9.30 p. m. Its duration was therefore 9 hours. The central calm 

 passed St. Thomas in 0.6 hours. As in the previous case, we designate 

 the radius of the calm space by a = 0.3 hours = 3.6 miles, since the 

 velocity of its progress must, according to the observations, be taken at 

 12 miles per hour; therefore the radius of the whole whirl (adopting 

 the previous notation) is a + £"= 4.5 hours = 54 miles, and therefore 



— ' — = 15 and — = 14. 



a a 



If we substitute these values in equation (3), we obtain — 

 X = 2.31og(l + 14|.)-0.032tang-'^14-|.f 0.5777|(o.214-^) 



+ 0.0625 ^ I Cff- 0.107 -^ + 0.015 J . 



V/hence for the following values of jr we obtain the corresponding 



values of X and z : 



^= 0.1 0.2 0.3 0.4 0.5 O.G 0.7 0.8 0.9 1.0 



X= 0.87 1.31 1.58 1.78 1.03 2.04 2.12 2.10 2.24 2.27 

 z =10.0 17.0 21.5 24.5 27.0 28.5 29.5 30.5 31.0 31.7 



