234. 



KNOWLEDGE. 



[Dboember 1, 1898. 



Motions in the line of sight at the sun's limb 

 corresponding to three hundred miles a second 

 have been observed, and since we know that a 

 radial velocity of three hundred and eighty-three 

 miles a second at the level of the photosphere 

 would suffice to carry matter permanently away 

 from the sun, it seems probable tliat prominence 

 matter occasionally moves in directions very con- 

 siderably Luclined to the radial, but such lateral 

 motions can, it seems to me, be as easily ac- 

 counted for on the wind theory as on the explosion 

 theory of the origin of solar prominences. — A. C. 

 Eanyakd.] , , , 



LIGHTNING PHOTOGRAPHS OR PHOTO- 

 GRAPHIC DEFECTS. 



Gore Lodge, Glenageary, co. Dublin. 

 14th October, 1893. 



To the Editor of Khowledge. 

 SiK, — I enclose two photographic prints, which 



I am told may interest you ; they are from 

 negatives exposed under the following circum- 

 stances. During a holiday in Switzerland, at 

 the latter end of August last, on a beautiful 

 moonlight night, I was tempted to expose a plate in a 

 small hand camera, the exposure, which was made from 

 my bedroom window, being one hour, from about 10 to 



II p.m. Next morning I took a snap shot of the same 

 scene ; the prints I send are from the resulting negatives. 

 The peculiar marks on the " moonlight " print showed up 

 in the negative soon after placing in the developer, and I 

 was at first inclined to throw the negative aside thinking 

 it had been spoiled ; for, owing to my plates getting mixed, 

 I did not at the time know I was developing the moon- 

 light exposure, or I might have treated it in a different 

 manner, with perhaps better results. I can only attribute 

 the zigzag marks to lightning, and thinking they are such 

 I send the prints to you, understanding you would be 

 interested in examining them. 



I shall be pleased to have your opinion, or to give you 

 any further particulars in my power. 



Yours truly, 



Robert R. Levingston. 



FlO. 1. — Moonlight photograph, exposed ihiriiij; one hour. 



Fig. 2. — Photograph of tlie same Tiew takeu the next morning. 



[In answer to a letter asking for the focal length of the 

 camera with which the photographs were taken, and 

 inquiring whether Mr. Levingston had seen any lightning 

 or heard the sound of thunder during the moonlight ex- 

 posure, he replied : — ] 



Gore Lodge, Glenageary, co. Dublin. 

 23rd Oct., 1893. 

 Dear Sir, — I delayed replying to your kind letter of 

 19th inst., to procure the particulars you ask for as to 

 "focal length" from a friend who has purchased from 

 me the little camera in which the photographs referred to 

 were taken. 



The camera has, I learn, a " focal length " of 45 inches. 

 The night on which the "moonlight" picture was taken 

 was an extremely bright moonlight night, and, by way of 

 experiment, I placed the camera on the window-sill, giving 

 just an hour's exposure. I was not aware of any lightning 

 or thunder, but there were no marks on the plate when I 

 put it into the developer, and the " Ivihtning" {.') marks 

 developed out in a most regular manner, the briijhter 

 parts coming out very quickly after putting into the 

 developer ; furthermore, the line mark at the edge of 

 the slide is quite clear in the negative, and no 

 " lightning " marks appear underneath or outside this 

 line, where, of course, the light did not act. I am led 

 to refer to the latter specially, because the Editor of 

 Pholoi/rajilii/ hinted that the marks may have been 

 pencil marks. 



You are quite at liberty to publish the photos, and if I 

 can help by any further details, I shall be glad to do so. 

 Yours truly, 

 A. C. Ranyard, Esq. Robert E. Levingston. 



[If the marks on the moonlight photograph were 

 due to lightning the flash must have been very close 

 to the hotel window, for it will be noticed that the 

 band of light seems to run into a complicated knot or 

 tangle in front of the branch of a tree at no great 

 distance in the left hand foreground. Such a flash of 

 ordinary lightning, discharged so close to the hotel, 

 would probably have been accompanied by a clap of 

 thunder which the visitors at the hotel could hardly 

 fail to have heard. 



Though the trace upon the plate has a general 



