Nolan — Mobilities of Ions Produced hy Spraying. 21 



axes and in various units. They all deal with negative ions. As has been 

 already mentioned, no positive ion of this mobility (with one very doul^tful 

 exception) was observed. 



It is clear from the curves that the number of ions of this mobility is 

 small in comparison with the others present. But there is hardly any room 

 for doubt that such ions exist. The method of measuring mobilities employed 

 during this work is not very suitable for sorting out small quantities of ions 

 of high mobility. It is hoped that by use of a different method a better 

 knowledge of all the more mobile groups, and especially of the last group, 

 may- be obtained. 



Unclassified Molilities. 



As in the case of the slower ions, we find that certain mobilities occur 

 which do not fit into any of the groups. Of these the most remarkable are 

 •67 negative and -80 positive. These mobilities are deduced from very good 

 observations, and cannot be considered to be open to doubt in any way. These 

 observations tend to cast some doubt on our idea of coexistent groups of ions 

 each of definite and unchanging mobility. In dealing with the slower ions 

 we were able to single out the ion of lowest mobility, and to show that the 

 mobility of this class did not change with time. If Table I is referred to, and 

 the positive and negative considered together, the reason for making this 

 conclusion apply to all five classes will be understood. Classes 1, 2, and 3 

 appear on the same curve, and are found practically unchanged at rates «, I, 

 and c. At the last rate a new ion can be observed (no. 4). This ion, as 

 well as no. 3, is unchanged in passing from rate c to rate d It is found again 

 at rate/ with another ion (no. 5). The latter must be a new and distinct ion. 

 It cannot be, say, no. 1 or no. 2 in the process of growth, for we have, so to 

 speak, kept in touch with these. As far as we can see this ion is of unvarying 

 mobility, as there is no change in passing from rate / to rate h. If Tables I 

 and 1 V are considered together, it will be seen that an attempt has been made 

 to continue this process of "keeping in touch " throughout. At each rate 

 as many ions as possible were observed and observations were made at a great 

 many rates. Except in this limited manner, i.e., by keeping in touch with the 

 slowest mobility through the overlapping of observations at different rates, 

 we cannot earmark any group of ioirs and measure its mobility after different 

 time-intervals. But we have at least been able to show that these groups 

 are separate and distinct, and that the more mobile are not merely an earlier 

 form of the slower ions. But even if each observation were isolated and 



