CLAYTON. — THE ECLIPSE CYCLONE. 309 



from opposite directions during this time. The penumbra is used to 

 indicate the area of partial eclipse, and the umbra to indicate the area of 

 total eclipse. The mean wind and the eclipse wind were at first deter- 

 mined graphically for all the stations ; then as the results seemed to be 

 of importance, they were rigidly computed for all the stations where the 

 observations were sufficiently accurate to warrant it. These results, 

 when plotted, indicate very clearly an outflow of wind from around the 

 umbra, and an inflow around the borders of the penumbra. 



But there are certain irregularities due to the normal irregularities 

 of the wind. In order to diminish the effect of these, I smoothed the 



observations by the formula . These winds were plotted 



at their proper places on maps of the United States for 8.15 a.m., Toth 

 meridian time, when the umbra was about to enter the American conti- 

 nent from the Pacific, and also plotted for 9 a.m., when the umbra had 

 passed off the coast of the United States on to the Atlantic. These maps 

 are shown in Figure 3. The position of the umbra is shown on each 

 map by a dark circular area. The depressions of temperature by the 

 eclipse are shown by numerals on the maps, and isotherms are shown by 

 dotted lines. The weather conditions are indicated by symbols, and the 

 direction and velocity of the eclipse wind are indicated by the direction 

 and length of the arrows. The winds were practically reversed in direc- 

 tion as the umbra moved from one side of the continent to the other, 

 but both charts show a distinct anticyclonic circulation and an outflow of 

 air extending from the umbra, or central area of the eclipse, to a distance 

 of about fifteen hundred or two thousand miles. In the 8.15 a.m. chart 

 the outer limit of the outflow appears to be in New York, beyond which 

 there is an inflow. In tliis chart the stations of observations are so far 

 in advance of the central area of the eclipse that no appreciable depres- 

 sion of temperature is shown ; but in the 9 a.m. chart, which coincides 

 with the greatest depression of temperature at Wadesboro. Washington, 

 and Virginia Beach, there is a central area shown by the isotherms where 

 the depression of temperature exceeds 8° F. This area of greatest cold 

 lags behind the umbra about five hundred miles. 



The charts in Figure 3 show only a portion of the eclipse area, or 

 penumbra, which was about iive thousand miles in diameter. Hence the 

 charts do not give an idea of the winds on the outer area of the penum- 

 bra, or the successive changes which occurred at any one station as the 

 eclipse passed over it. A view of these changes is obtained by plotting 

 the winds, temperature, etc., at given stations when they were successively 



