ADVERTISEMENT. 



In tlie present investigation, on the "Structure of the Nucleus," the author 

 answers certain practical questions suggested by the last memoir (Experiments 

 with Ionized Air, in Smithsonian Contributions to Knowledge, Vol. XXIX, 1901), 

 in relation to phosphoi-us wlien used as a source of nuclei ; /. e., of extremely small 

 particles tending to precipitate water from moist air, when this is suddenly cooled. 

 It is, however, the chief aim of the memoir to throw light on the phenomena con- 

 nected with the presence of nuclei in air, by aid of the coronas or color rings seen 

 in such air when its moisture is condensed and deposited on the nuclei and a 

 distant source of light is looked at through the turbid medium. As these coronas 

 occur in great variety and size, they lend themselves for measurement when other 

 means fail. A systematic study is thei'efore made at the outset of the number of 

 particles corresponding to all well-defined members of the sequence of coronas 

 obtained under known conditions of supersaturated air. The numbers run from 

 less than 100 to upwards of 50,000 per cubic centimeter. 



The results are then applied in an endeavor to find the velocity of the nucleus 

 by non-electrical methods, l)otli of a direct and an indirect kind, utilizing the fact 

 that if nuclei leave the medium, the coronas obtained under like conditions must 

 change correspondingly. Throughout the latter i)art of the investigation the 

 nuclei are purposely produced in the simplest manner possible, by shaking solutions 

 in air; but in the course of the investigation the author reaches conclusions which 

 seem to show that the solutioual nucleus is of nuich broader meteorological signifi- 

 cance in its bearing on atmospheric condensation and electi-icity, than has. hereto- 

 fore been anticipated. It appears that in an unbounded region of the atmosphere 

 saturated with watei", this nucleus must be a peisistent structure. This he finds 

 is strikingly apparent even when the air is saturated with very volatile liquids 

 othei' than water. 



In C(mclusion the author points out that the size of the nucleus must vary 

 with the medium in which it is suspended and that water nuclei, in particular, 

 will depend for their dimensions on the meteorological status of the atmosphere. 



