308 



PROCEEDINGS OF THE AMERICAN ACADEMY, 



The outside vertical lines B and E show the beginning and end of partial 

 eclipse, and the central vertical lines T show tlie times of total eclipse. 

 The dotted straight line connects the observed temperature at the begin- 



7 A.M 



8 A.M. 



9 A.M. 



10 A.M. 



Figure 1. 



ning and end of the eclipse, and represents the interpolated uniform 

 change. The observed temperatures are shown by the unbroken curved 

 line, and the departures of these from the values represented by the dotted 

 line is assumed to be the depression of temperature arising from the 

 eclipse. The pressure, humidity, and vapor tension were treated in the 

 same manner. 



In order to obtain the eclipse wind in velocity and direction, the 

 observations were treated in the following manner. 



In the accompanying diagram, Figure 2, let A B represent the direc- 

 tion and velocity of the wind prevailing independent of the eclipse, and 



Figure 2. 



A C the wind observed at any moment during the eclipse ; then com- 

 pleting the parallelogram of forces, A D will represent the eclipse wind 

 in direction and velocity. The prevailing wind was derived from the 

 mean of the winds immediately preceding and following the penumbra, 

 or, what was found to be practically the same thing, from the mean wind 

 direction durhig the passage of the penumbra, since the eclipse wind was 



