140 



A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



15, 1903, wei-e originally made with reference to an arbitrary' scale of nucleation. 

 There are many reasons why it wotild be difficult to reduce them accurately to 

 the uniform scale of the present chapter. Among these, frequent changes of 

 ajiparatus, measurement of aperti:re to the red ring, and the absence of a variety 

 of details of record discouraged such an attempt. The reduction, therefore, is 

 approximate; but the values of nucleation are roughly absolute and quite 



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1 



Figure i.- — Diaoram Showing General Disposition of Apparatus. 



satisfactory as relations, and they thus meet most of the demands made ttpon 

 them. In view of their preliminary character they will be given in charts 

 only. In these cases the condensation chamber was a large aspirator flask 

 (fig. i), placed horizontally so that the measurement of aperture was made 

 parallel to the axis of the cylinder. 



The second group of observations (by far the larger nttniber) from March 

 15, 1903, to October 31, 1904, were obtained with apparatus perfected as ex- 

 plained above. These will therefore be given both graphically and in tables. 

 The latter will contain a variety of relevant data. 



FIRST GROUP OF OBSERVATIONS. 



4. Early observations. — The charts Nos. 1-12, comprehending the first 

 group of results, follow. The nucleations, n, are laid off vertically, and in 

 charts 1-8 they are given in full (n nuclei per cubic centimeter). In the re- 

 maining charts (Nos. 9, ct seq.) the number of nuclei are given in thousands 

 {n X 10"') for brevity. The temperature and winds (for 8 a.m.), taken from the 

 weather maps of Block Island and Nantucket, will often be entered, but as 

 the work progressed superfluous data were gradually dropped. In some of the 

 charts the changes of temperature, St, and of barometric j^ressure, 6p, are also 

 given, with the occurrence of clear weather, 0, cloudy, # and partly cloudy 

 (J weather, sunshine S, rain R, snow Sn, cold wave c.w. or — S, etc. Refer- 

 ences to Fahrenheit and to centigrade are indicated. 



The nticleation (chart i) begins low on the 2d of October, 1902, with the 

 rain, but thereafter increases nearly fourfold with the bright weather of the 

 succeeding days. Note the prevailing winds from the north ( )n the 5th and 6th, 

 clouds and rain usher in a second minimum. On the fair days succeeding the 



