NUCLEATION AT BLOCK ISLAND. 103 



In March the maxima are less pronounced ; they occur on the ist 

 to 3d, nth, i3th to i6th, and 26th. Minima of longer duration than 

 heretofore accompany the rains of yth to ioth, igih to 2ist, 23d to 

 25th, and 2Qth to 3ist. One may note the midday minima on the is t, 

 2d, and 3d. The 4th shows a reversal of the usual agreement between 

 the wind and nucleation. On the yth the readings fall during the 

 day as rain sets in. The wind on the i3th, i4th, and isth changes 

 suddenly, near noon, from northeast to southwest, but no definite 

 corresponding change appears in the nucleation. A fine cloud effect 

 is shown on the i6th when the sky becomes overcast in the afternoon. 

 On the 23d one may note a minimum, as the wind passes through the 

 east to south. 



The variations in the nucleation in April are even less marked ; low 

 maxima occur on the ist, 3d, yth, and i4th to i6th, while minima 

 accompany rain and fog on the 4th to 6th, and ioth to I4th. An 

 unusually low value is obtained on the 2d, with clear northwest wind, 

 and on the yth is an unaccountable high reading which seems to have 

 no connection with local influences. From the i6th the weather is 

 warm, with considerable fog, and the nucleation runs low, with little 

 variation to the end of the month. 



19. Summary and comparisons. In figures 91 and 92 are shown 

 together the current nucleatious (continuous heavy black line), sun- 

 shine (continuous light black line), vapor pressure (heavy broken 

 line), temperature (light broken line), and general weather conditions 

 for each day. The nucleation and temperature given is the average 

 of the observations taken during the day, as is the vapor pressure 

 after March 28th ; before that date the vapor pressure is the mean of 

 the regular morning and evening observations at the station. Both 

 the temperature and vapor pressure are laid off positively downward. 

 The sunshine is the total for the day as recorded by the office sunshine 

 recorder. 



The graph as a whole shows a rather marked similarity in the nature 

 of the several curves. In many cases of discrepancies the nucleation 

 appears to show the effect of conflicting causes. On November 29, 

 with no sun, the nucleation persists from the fairly high reading of 

 the day before, although the other curves drop. Warm rain and 

 further increase of vapor pressure on the 3oth cut it down, and it 

 ascends very slowly during the cloudy days following. A decrease 

 accompanies the rise in temperature and vapor pressure of December 

 5, which is quickly reversed by the sunshine and northwest wind of 

 the 6th. The nucleation curve remains nearly level, as doss that of 

 the water vapor, during the two cloudy days succeeding. The sun- 



