78 THE STRUCTURE OF THE NUCLEUS. 



Thus tbe axial colors flash through a variety of tones, teiminating iu opaque, 

 which is hei'e a mere evidence of irreguhir size. Very little reliatice can therefore 

 be placed on the color sequences, but the luarked occurrence of axial color is well 

 Imiught out. 



The following table is a full series of e.xperiineuts made to deteruiiiie the coro- 

 nas in gasolene vapor. They were obtained in a glass globe, 23 cm. in diameter, 

 with careful filtration. Some of the coronas are measured. 



TABLE 3— BEHAVIOR OF PUNK NUCLEI IN GASOLENE VAPOR. GLOBE, 23 cm. IN 

 DIAMETER EXHAUSTION, 76-59 cm. DIA.METER OF DROPLETS d, IN cm. 



Here the initial fog floats gravitatioiially on the oleai' air below, as the punk 

 nuclei were introduced from ^lowins; charcoal. 



11. Sjyontaneous nudeation. — If the nuclei are left standing, they are liable 

 to persist for iiiany hours, and good coronas (nucleation now homogeneous) may be 

 obtained on the succeeding day. A clean vessel, however, remains clean. There 

 is no spontaneous nucleation. 



Thus, I found in a ve.ssel freed from nuclei by exhaustion at 9'' 50'", no coronas 

 or rain at 1*" 10"", nor at 2'' 45™. Similarly, when left over uight, the clean vessel 

 remained free from nuclei. 



12. Shaken nuclei. — On shaking the gasolene violently, coronas were pro- 

 duced as follows: 



Exhaustion, i 



Corona, Strong s ■ 



d: 



It is noteworthy that the nuclei of these coronas are themselves very persistent. 

 Examined 7 minutes after shaking, the corona was of undiminished strength ; 

 after 30 minutes it was scarcely weaker. It will be seen below that nuclei so 

 obtained are as persistent as any other kind, and may be traced 15 or 25 hours 

 after shaking. They cannot, therefore, be gasolene globules, which would vanish 

 instantly, but rather (at first sight) the residual solute of a dilute .solution. The 

 examination of water, however, in wliich both solid and gaseous solutes were 

 tested, showed that they are concentrated solutions and that they persist in view of 



