vi EDITORIAL NOTE 



the observed values. They show a range of 13 per cent from a 

 minimum about January i to a maximum about July i. 



A comparison of Wolfer's observations with those made by me 

 at Canton, Massachusetts, shows that the annual variation is con- 

 siderably less at Canton so that the period is no doubt of terrestrial 

 origin and probably arises from the lower visibility in Europe during 

 winter on account of the increased cloudiness combined with the low 

 altitudes of the sun. 



It seems probable then that Wolfer's numbers should be multiplied 

 by these percentages with opposite signs to those given and added 

 to the observed numliers. at least since the year 1856. 



H. H. Clayton. 



