26 



THE STUUCTFEE OF THE NTJCLETJS. 



the liquid coiitaiiit'il, the charged air again becomes homogeneous as to nuclei and 

 the coronas uniform, though this shaking introduces a new phenomenon. With 

 henzine, etc., gradual distortion of the coronas will lepeatedly occui-, and for this 

 reason the following results refer to water vapor exclusively. Distorted coronal 

 display will he taken u[t later. 



The time during which a given charge remains activ^e if not interfered with is 

 indefinitely long, but with a continually progressing evanescence of nuclei. Coronas 

 are well i>roduced three hours after charging. They occur faintly and contracted 

 in foi'ui even after more than twenty-four hours. In such cases there are many 

 mysterious (jualitative changes, which will be treated in turn beluw. On standing 

 over night, rain-like preci[)itation is apt to occur. Fogs may be spontaneously 

 produced in a highly nucleated receiver without any supersaturation whatever. 

 On the other hand, coal gas cari'ies nuclei indefinitely, as if they were part of 

 itself. 



7. Observations with small ghhes. — The infoi-raation first to be sought is some 

 practical classification of the sequence of coronal colors, and of the axial colors 

 seen in these experiments. The latter have already been leferi-ed to as the flame 

 colors seen along ah, figui-e 3 ; the others are largely diflFi-action colors seen along 

 ach. It will l)e found that these colors are very tlift'eient. If the corona has a 

 central field other than white, the axial color is always nearly complementary to the 

 cential patch of the corona. As the cloud particles grow in size, both central color 

 phenomena pass thi'ough Newton's seiies, at a definite phase difference apart. 



I give in the following table certain preliminary results obtained with a small 

 globe, but 23 cm. in diameter. The numerals in the first column relate to table 4, 

 as a standard case, and show the number of exhaustions there needed to reach a 

 similar corona. The remaining columns show the number of exhaustions made 

 with the present apparatus, to obtain the adjoining color sequence, the colors 

 being reckoned from within outward. An attempt has been made to airange both 



TABLE 1.— PRE1.1MIN.\RY 

 DI.\METER 23 cm. 

 D=ioo cm. 



D.\T.\ FOR CORONAL COLORS. SMALL GLOBE, 

 EXHAUSTION 76-63 cm. DISTANCE OF SOURCE, 



Use of hot water tried, but without advantages. 



