74 Beams of Light as if emanating from Flames. [June 16, 



gas; then lowered the upper eyelid and saw the downward tail 

 remaining when the gas flame was eclipsed by the eyelid. The 

 theory of all this is clear to me, and in agreement with what I have 

 previously devised. J. T. 



Take notice that to get the phenomena above sketched out to show 

 themselves, the edge of upper eyelid, where roots of eyelashes are 

 situated, must not shadow the prismoid when the eyelid is lowered 

 enough to cover the pupil from the direct rays of the candle or gas 

 flame. After the candle is cut off from the pupil, the direct rays 

 from the flame must still be reaching the prismoid. This, I think, 

 tallies with the experimental conditions under which the tail was seen 

 when the flame was eclipsed by eyelid. J. T. 



p.S. Same day, 29th December. On a little further consideration 

 I notice that the elevation of the face is of no importance. It is only 

 the elevation of the line of special direction of the eyesight [axis of 

 the eye] relatively to the line from flame to eye that is important. 

 J. T. 



Notes on Quasi-Light Beams. 

 (For paper.) 



Often I fail to see the apparently ascending beam above the 

 candle or gas flame. But I find that by very nearly shutting the eye 

 I can see the ascending beam going up very high and the descending 

 one at same time. On bringing my open hand down from above as if 

 to cut off the ascending beam I- see the beam as if between my eye 

 and my hand, and the flame begins to be eclipsed before the beam is 

 cut off, or even diminished. 



Note by the President of date June 16. 



I had asked many friends well acquainted with optical subjects 

 whether they knew of this explanation of the luminous beams, and 

 all said no until yesterday evening, at the soiree of the Royal Society, 

 when Professor Silvanus Thompson immediately answered by giving 

 the explanation himself, and telling me that he had given it to his 

 pupils in his lectures on optics, as an illustration of a concave 

 cylindrical lens. He did not know of the explanation ever having 

 been published otherwise than in his lectures. I have myself also 

 looked in many standard books on optics, and could find no trace of 

 intelligence on the subject. It seems quite probable, therefore, that, 

 of all the millions of millions of men that have seen the phenomenon, 

 none, within our three thousand years of scientific history, had ever 

 thought of the true explanation except Professor Silvanus Thompson 

 and my brother. 





