Sun-spot Areas and Diurnal Temperature- Ranges. 305 



couplets of similar period even if these might be remote from a 

 position of maximum Inequality. But as it is we must confine 

 ourselves to positions near some maximum in making our compari- 

 sons, and inasmuch as the Toronto temperature-range Inequalities 

 presenting two fluctuations in 24 days are virtually short period 

 Inequalities, we have preferred to take the positions of maximum 

 Inequality from them rather than from the sun-spot records. 



Thus, for instance, referring once more to Table II, we find a 

 Toronto maximum at 33, and a sun-spot maximum at 30. We 

 have chosen 33 as our period, and have altered the solar maximum 

 at 30 in phase so as to make it indicate 33, and so on with other 

 couplets. 



Furthermore, in each case we take the mean of three series. Thus 

 in the instance now recorded we have taken the mean of sun-spots at 

 29, 30, and 31 all reduced to 33, and have compared with 

 this the mean of Toronto ranges at 34, 33, 32 all reduced to 

 33 likewise, and so on for other couplets. Finally, in Table III, 

 each series has been reduced so as to represent the sum of 12 years 

 Inequalities, and the sun-spot series have been equalised in the same 

 way as the terrestrial observations, because in instituting any 

 comparison with respect to magnitude it is desirable that the same 

 treatment should have been applied to both. 



In a previous part of our paper (Art. 15) we spo'ke of a subsidiary 

 service which was to be rendered by the Kew temperature- ranges. 

 We propose to regard these as terrestrial pointers of indicators by 

 the aid of which we may distinguish the one Toronto maximum from 

 the other. It will be found that one of the Toronto maxima occurs 

 in date about 8 or 9 days before the single maximum of the corre- 

 sponding Kew Inequality. This Toronto maximum, so indicated by a 

 strictly terrestrial method, we have fixed upon as our starting point, 

 and at this point all the Toronto Inequalities in Table III are made 

 to begin. The Toronto Inequalities thus placed are then compared 

 with sun-spot and Kew temperature-range Inequalities of similar 

 period, so arranged that the three members of the same triplet 

 always start on the same day ; in other words, the numbers on the 

 same horizontal line and belonging to the various members of the 

 same triplet denote simultaneous phenomena. 



In order to make this comparison it is necessary that the Inequali- 

 ties compared together should be consistent with their prevalent type ; 

 for instance, the Kew temperature-range Inequality must present a 

 single maximum and minimum sufficiently well at least to admit of 

 serving its office as a pointer. In like manner the Toronto tempera- 

 ture-range must be a double, and the sun-spot a single Inequality. 

 We must, therefore, examine the couplets of Table II in order to see 



