56 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



GENERAL WEATHER CONDITIONS. 



Tlie sky during the early portion of the 6th of May was partly cloudy, and the clouds 

 threatened rain. Slight showers occurred between 8.00 and 9.00 a. in., and a heavy shower at 

 9.15 a. m., after which the sky cleared. But at no time during the day was the atmosphere free 

 from a haze, which was apparent to the eye and also showed itself in the readings of the instru- 

 ments. The relative humidity was above the average, being 81 per cent, at noon and 74 per cent. 

 at 2.00 p. m., and the radiation instruments gave lower readings than on other days, especially in 

 the morning. Passing clouds prevailed during the day, but interfered only a little with the 

 observations of the eclipse. At the first and fourth contacts there were no clouds in the vicinity 

 of the sun. Itnniediately after the second contact a light clou<l i)a8sed over the eclii)sed sun, and 

 remained for a portion of the first minute of totality. There wei-e no clouds during the remainder 

 of the total phase, but immediately after third contact a cloud again covered the sun for forty 

 seconds. Another cloud, heavier than its predecessors, obscured the sun for several minutes, 

 beginning with the fifth minute after third contact. It will be seen from the above that the 

 observers were especially fortunate in the weather at the time of totality, but it should be remem- 

 bered that at all times the atmosphere was hazy. The wind blew steadily during the day, aver- 

 aging 8.3 miles an hour, as recorded by the anemometer 9 feet 7 inches above the ground. 



BAROMETRIC PRESSURE. 



The barometric observations show a slight, but well marked, rise in pressure during the 

 eclipse. In order to determine whether this phenomenon has any real relation to the eclipse it is 

 necessary to inquire whether a similar result might not have occurred on other days, and, also, 

 what was the usual course of pressure between 10.00 a. m. and 1.00 p. m. The regularity of move- 

 ment in the pressure from day to day renders such an inquiry possible, even though the observa- 

 tions extend over a short period. 



On six days preceding the eclipse half-hourly observations of pressure were made between 

 10.00 a. m. and 1.00 p. m. These reduced are as follows: 



' Missing values interpolated. t This reading jiiolialdy should be 29.797. 



