20 



Proceedings of the Royal Irish Academy. 



As before, the numbers that are considered specially good are marked 

 with an asterisk. For the classes 6, 7, 8, and 10 the means given are the 

 means of the numbers thus distinguished. For classes 9, 11, and 12 the 

 means given are obtained from all the results,' excludtug those marked 

 doubtful. 



It has not been thought necessary to give examples of the curves from 

 which these mobilities have been deduced. In general they do not differ 

 in character from those that have been alreadv shown. The mobilities 



numbered 9, 11, and 12 have been difficult to establish. The quantity of 

 each of these ions present is very small. Consequeutly the corresponding 

 bends on the current-voltage curve are very faintly marked. Of the ten 

 observations of class 9 only one can be regarded as thoroughly satisfactory. 

 Similarly in class 11, there are only two good obser\ations out of thirteen. 

 Less attention, however, was given to those classes than to class 12. "When 

 indications of this class were obtained, carefid experiments were made in 

 order to verify its existence, as the mobility was considered to be remarkable- 

 high. The curves from which the values of mobility of this class are deduced 

 are all given in tig. -5. These curves are for convenience plotted to various 



