132 



KNOWLEDGE. 



[June 1, 1895. 





With reference to the results given in my paper on 

 " Globular Star Clusters," as an increase of 1-5 magnitude 

 in the sun's stellar magnitude implies an increase of its 

 computed brightness about four times, it 

 would be necessary to remove it to double the 

 distance given in my paper in order to reduce 

 it in brightness to stars of the fourteenth 

 magnitude. This would double the diameter 

 of Omega Centauri, which is supposed to be 

 placed at the same distance, and would pro- 

 portionately increase the distance between 

 the components of that wonderful cluster 

 of suns. 



In excluding refraction from the originating causes of 

 the sun pillar, Kaemptz raises a difficulty in explaining 

 the parhelia described by Roth ; for it is admitted that 



THE SUN PILLAR. 



By the Rev. Samiel Barber. 



THIS very unusual and striking optical 

 phenomenon was seen in its full 

 brilliancy, though only for about 

 fifteen minutes, at Westnewton, near 

 the Cumberland coast, shortly before 

 sunset, on January 30th, 1895. The unusually 

 severe frost prevailing at the time was cha- 

 racterized by other rare appearances, c.;/., 

 the white rainbow formed in the upper sky. 



This sun pillar was highly lumioous, almost 

 like a continuation of the sun itself, making it 

 appear like a huge comet with a tail of even 

 breadth with its own disc, and equally brilliant 

 in its entire length. Light fleecy clouds, not 

 cirrus, but a loose drift of half stratified " altn 

 cumulus," were drifting above the declining 

 orb of day from E.S.E. I may note here that 

 this variety of cumulus certainly contains, at 

 times, quantities of ice-prisms. It has been 

 almost continually prevalent during the long 

 frost of January and February, 1805, accom- 

 panied by bands of strato-cumulus of loose 

 texture and smoky tint. The occasional 

 formation of a pseudo-nimbus in the east, 

 soon to clear away, was another characteristic 

 of this frost. A simOar phenomenon occurs 

 during drought in summer. 



The appearance of the sun column as 

 observed by Roth is recorded in Kaemptz 's 

 "Meteorology." This observation of Roth 

 was most remarkable, the column having appeared before 

 the sun had risen, and containing a parhelion, which 

 was mistaken at first for the true sun. The sun shortly 

 after rose, and the column of light followed underneath it 

 and contained anutlur parhelion. 



Kaemptz himself has hit upon the right explanation of 

 this phenomenon, by a careful deduction fi-om an observa- 

 tion which he made on January 23rd, 1888. On that 

 occasion both the upper and lower parts of the column 

 were visible ; many luminous frozen particles were 

 floating in the air, and upon examination these proved to 

 be isolated hexahedral jilms, about the size of a pin's head. 

 Kaemptz rightly points out that there are no phenomena of 

 refraction here ; it is simply reflection, and in this he 

 agrees with Brandes. 



The observation now recorded, taken by myself at "West- 

 newton, is valuable as agreeing with and confirming 

 Kaemptz's account, which is, indeed, a model of exact 

 description. The height of the above column was similar 

 in both cases, the air contained ice-crystals, and the 

 breadth of the column was also the same. 



Suu Pillar 



seen at West Newton, Cumberland, January 30tli, 1H0.5. 

 (From a sketch bv Rev. S. Bakbee.) 



refraction is the usual source of these latter appearances. 

 They almost invariably exhibit the colours which corre- 

 spond to the refraction angles of ice-prisms. But for all 

 that, it is undoubtedly reflection which must account for 

 the sun pillar. 



Let the reader consider the case of the long column of 

 light cast by the sun upon the smooth surface of a lake, or 

 a calm sea, when near the horizon. Though broken by a 

 slight movement of the water, the bright band is normally 

 of the same width as the sun's apparent disc, which has 

 its full diameter projected upon the watery mirror through- 

 out the whole length of the column, wherever equiangular 

 incidence of the light is possible. This equiangular 

 incidence is, of course, only possible in a line drawn directly 

 from the observer to the emitting body of light, whenever 

 the reflecting surface is horizontal. Thus, bands that 

 seem to pass horizontally through the sun are produced 

 by the reflecting facets of crystals floating vertically ; but 

 upright columns which pass vertically through the sun's 

 disc are the result of crystals or prisms that float 

 Imri-iintdUy. 



