CHAPTER IV. 



THE NUCLEATION OF THE ATMOSPHERE AT BLOCK ISLAND. 



BY ROBINSON PIERCE, JR. 



74. Introductory. The present series of experiments, during the 

 winter of 1904-5, was undertaken with a view to comparing the nucle- 

 ation in pure country air with the results obtained at the same time 

 in Providence.* After a consideration of several places, Block Island, 

 R. I., was chosen as a station, on account of its location, in the ocean 

 (see fig. 94) 10 miles south of Point Judith, and the freedom from 

 smoke and other refuse commonly found in the air of cities. At the 

 same time, the two stations are, in other respects, meteorologically 

 nearly identical. Through the courtesy of Prof. Willis L,. Moore, 

 chief of the United States Weather Bureau, the office of the Bureau 

 on the island was placed at our disposal, and the apparatus was duly 

 installed there during the latter part of November. The chief occu- 

 pations on Block Island are fishing and farming, and the only smoke 

 is that from dwellings, which are to a great extent scattered. As the 

 high readings usually occurred with north to west winds, the situa- 

 tion of the Weather Bureau building northwest of the village gave 

 complete freedom from all such local influences. 



I have here to express my thanks to Mr. W. I,. Day, the local 

 observer, for his assistance in many ways during my stay at the island. 

 Mr. Day took the observations at various times, and the results from 

 March 10-14 an d April 19-25 are his. 



75. Apparatus. The apparatus used was similar to that employed 

 by Professor Barus,f and the two were operated side by side for some 

 time previous to leaving Providence, with results well in accord. A 

 brass cylindrical trough was substituted for the wooden one late in 

 December and a few minor changes were made from time to time, all 

 of which were tested to make sure that they did not affect the read- 

 ings of the instrument. 



*C. Barus : Smithsonian Contributions, Vol. xxxiv, 1905, Chap. IX; also Chap. V 

 of the present memoir, 

 t Barus : Loc. cit. 



