SOLAR HALO. 63 



probably due, as has been set forth, to local atmospheric con- 

 ditions. 



Figure 4 is added to the list simply that a comparison can 

 readily be made of the recent halo with a typical display in 

 the past, as observed and described by F. X. Sawyer, of 

 Brighton, England, on June 5th, 1875. I'See Enc. Brit., 

 IX Ed., Vol. XI, p. 356 J. 



In support of the opinion that local and irregular condi- 

 tions existing in the cloud plane would materially affect the 

 view of such a phenomenon, attention is called to Figure 5. 

 The long horizontal lines represent the cloud strata, or atmos- 

 phere charged with innumerable, minute ice crystals. The 

 distribution of these crystals is represented by short horizon- 

 tal and slant lines. The rays of sunlight before passing 

 through the plane are shown by long vertical lines, and their 

 direction by arrowheads. The long, converging lines repre- 

 sent the refracted and reflected rays entering the eye after 

 passing through the cloud. The phenomenon is considered 

 as being observed -from points A, B and C, at say ten mile 

 intervals apart. 



If the cloud is to be considered as being of uniform thick- 

 ness throughout its whole extent and the distribution of the 

 cr\-stals is considered as similarly uniform, the observer at A, 

 B and C, if on the same lavel would, of course, see the same 

 details in ever\' respect. It is not reasonable to suppose, 

 however, that the cloud was of uniform thickness when so 

 many currents and tremendous pressures are continually dis- 

 turbing the balance of the upper air. 



One has but to recall the almost countless, varied shapes 

 of snow flakes he has seen to readily accept the statement 

 that the varieties of ice crystals in cloud formations, such as 

 cause halos, are quite as numerous in size and shape. Fur- 

 ther, it is not to be expected that an equal number of each of 

 these different shaped ice particles could be found grouped in 

 all parts of the cloud, even if the cloud was of uniform 

 thickness — much less than if. as it is fair to assume, would 



