96 THE STRUOTUKE OF THE NUCLEUS. 



a trace of coudeusation. There must be neither coronas, no matter how faint, nor 

 rain. All exhaustions are to be identical as to the pressure diflferences applied, 

 unless sjjccial purposes are aimed at. 



The receiver is now vigorously shaken, by jerking it sharply up and down a 

 di'hnite number of times. A rotational swirl of the li(piid contents is to be avoided, 

 as the friction of the liquid upon itself and not the rush of liquor over the spherical 

 •sides of the receiver is efficient in producing the nuclei. It will be shown that the 

 ([uantity of liquid contained, the violence of the agitation, the number of times 

 shaking is repeated, /. e., the number of jerks, etc., all materially influence the 

 result. There are, thei'efore, elements of vagueness inherent in the methoil, and at 

 first sight they might be supposed to be fatal. The results show that this is not 

 so, and that the utilization of the simple means for investigation has certain peculiar 

 advantages which make it desirable to carry the method thi'ough l)efore investigat- 

 ing more determinate methods of agitation. It is presumable, however, that a 

 scattering spray may be so installed as to yield a definite ma.ximum of nucleatiou ; 

 but thus far this has not been attempted. 



At specified times after shaking, the coronas are pioduced and measured. 

 Expeditious manipulation of the goniometer is here frequently necessar}', and it is 

 for this reason that the form of goniometer already described has been used 

 throughout. 



Filteied air is then introduced through F into H. Usually an intermediate 

 exhaustion is necessaiy to clear the air of nuclei, and must always be applied as a 

 test. AVhen the coi'onas are lai'ge, a certain number of the nuclei escape precipita- 

 tion. After shaking again, the experiment is repeated under the same or modified 

 conditions. 



4. Talrdated result.s. — The results are "iven in the following sei'ies of tables, 

 in which the first columns contain the pei'centage of dry salt or acid in solution. 

 The second columns show the amount of partial exhaustion, by giving the pressure 

 decrement below atmospheric pressure at which the corona is observed. The third 

 columns contain the time elapsed in minutes, after shaking ; the fourth, the number 

 of times the receiver was jerked up and down to generate the nuclei. 



The coliunns undei' .s ai'e the diameters of the coronas subtemled at the end of 

 the arm of the goniometer, here 30 cm. long, so that s/SO is chord of the apei'ture 

 of the coi'ona in any given case, for distances one and three metei's, respectively, of 

 the goniometer and light fi'om the center of the receiver. The most satisfactory 

 metliod of standardization is a direct comparison with lycopodium spores, of 

 diameter .0032 cm. These showed at different distances from the goniometer, if 

 the ])ositi(Uis of the latter and the light are fixed at 4 meters apart, ami if so is the 

 chord in (picstion, 



•95 meters s„ = i.oo cm. 



i.oo i.oo 



'•OS -95 



I.oo .95 



I.oo 



•95 



