A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



203 



of wind and weather is without effect on the nucleation. On the 20th there 

 is a cloud effect. No specific result marks the hail-storm of May 19. On May 

 17 and 31 there are low Sunday nucleations for clear weather, but the other 

 Sunday nucleations are high. 



40 



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Charts i6,'i7, iS, ig. 



10. In the beginning of June (charts 18, 19, 20) hazy weather and rela- 

 tively high nucleation are due, no doubt, to the New England forest fires, in 

 Maine and elsewhere, which occurred during a period of drought. Intensely 

 yellow fogs, red moons, and greenish suns were observed. The nucleation, 

 however, is by no means remarkably high, not more than twice the normal 

 summer values and scarcely one-fifth of the large winter values— in spite of the 

 excessive fogs. The copious rains which followed the period of droughts grad- 

 ually reduced the atmospheric nucleation to very small values (June 7-16). 

 The sharp maxima on June 17, 22, 23, are probably due to local fires. 



11. In the end of June and beginning of July (charts 20, 21, 22) the 

 nucleation is remarkably high and sustained, changes of wind and weather (June 

 30, July i), and even of high temperatvire (July 3), notwithstanding. Marked rises 

 of temperature and of nucleation concur. Sunday minima with clear weather 

 occur on July 5 only, July 26 being partly cloudy. The effect of gunpowder 

 smoke on July 3 and 4 seems to be quite absent. Rain on July 7, 22, 30 (the 

 latter is even followed by a maximum) scarcely reduces the nucleation, but low 

 values follow the rain-storms on July 18 and 21. The thunder-storms on July 

 10 and 15 without rain seem actually to be compatible with a rise of nucleation. 

 Incidental night observations on July 23, 26, and August i and 2 show no 



