NUCLEATION AT PROVIDENCE AND BLOCK ISLAND. 



129 



The chart, moreover, contains the average monthly nucleations 

 observed by Mr. Pierce at Block Island. It is interesting to note that 

 the general march here is the same as at Providence, a definite tendency 

 toward a maximum in December and then a relatively enormous maxi- 

 mum in February, from which there is slow descent to the summer 

 nucleation which would be nearly vanishing. To accentuate these 

 relations, figure 104 has been drawn, in which the nucleations at 

 Providence and at Block Island are given in ten thousands and in 

 thousands of nuclei per cubic centimeter, respectively. The same 

 February disturbance is thus superimposed on the high local nuclea- 

 tions due to combustion, etc., at Providence, which exists in compara- 

 tive freedom from local discrepancy at Block Island. It is hard to 

 resist the conclusion that so marked an interference with the usual 

 distribution of nucleation can result from local or terrestrial causes. 

 Thus, the average March nucleation at Block Island exceeds the 

 December nucleation, while the April nucleation is nearly as high as 

 the January nucleation. 



14 



'Une- 



-ri&Ws 



; -err 



* C/'-Kw_ . 



*!'^ 



Jlfucleatim. 



Jhnr. Stic. Jem. (Mr. Max J/r 



FIG. 104. Average monthly nucleations from November, 1904, to May, 1905, at Provi- 

 dence in ten thousands per cubic centimeter, and at Block Island in thousands 

 per cubic centimeter, showing the probable run of the curves in the absence 

 of the February maximum and the coincidence of the maximaland the minima. 



