46 Things not generally Known. 



was found an impression of a horse-shoe, similar even in size to that 

 fixed on the mast-head. 2. A sailor, standing in a similar position, 

 was struck by lightning, and had on his left breast the impression of the 

 number 4 4, with a dot between the two figures, just as they appeared at 

 the extremity of one of the masts. 3. On the 9th October 1836, a young 

 man was found struck by lightning ; he had on a girdle, with some gold 

 coins in it, which were imprinted on his skin in the order they were 

 placed in the girdle, a series of circles, with one point of contact, being 

 plainly visible. 4. In 1847, Mme. Morosa, an Italian lady of Lugano, 

 was sitting near a window during a thunderstorm, and perceived the 

 commotion, but felt no injury ; but a flower which happened to be in 

 the path of the electric current was perfectly reproduced on one of her 

 legs, and there remained permanently. 



M. Poey himself witnessed the following instance in Cuba. On July 

 24th, 1852, a poplar-tree in a coffee -plantation was struck by lightning, 

 and on one of the large dry leaves was found an exact representation 

 of some pine-trees that lay 367 yards distant. 



M. Poey considers these lightning impressions to have 

 been produced in the same manner as the electric images ob- 

 tained by Moser, Riess, Karster, Grove, Fox Talbot, and others, 

 either by statical or dynamical electricity of different intensi- 

 ties. The fact that impressions are made through the gar- 

 ments is easily accounted for by their rough texture not pre- 

 venting the lightning passing through them with the impres- 

 sion. To corroborate this view, M. Poey mentions an instance 

 of lightning passing down a chimney into a trunk, in which 

 was found an inch depth of soot, which must have passed 

 through the wood itself. 



PHOTOGRAPHIC SURVEYING. 



During the summer of 1854, in the Baltic, the British 

 steamers employed in examining the enemy's coasts and for- 

 tifications took photographic views for reference and minute 

 examination. With the steamer moving at the rate of fifteen 

 knots an hour, the most perfect definitions of coasts and bat- 

 teries were obtained. Outlines of the coasts, correct in height 

 and distance, have been faithfully transcribed ; and all details 

 of the fortresses passed under this photographic review are ac- 

 curately recorded. 



It is curious to reflect that the aids to photographic development -all 

 date within the last half-century, and are but little older than photo- 

 graphy itself. It was not until 1811 that the chemical substance called 

 iodine, on which the foundations of all popular photography rest, was 

 discovered at all ; bromine, the only other substance equally sensitive, 

 not till 1826. The invention of the electro process was about simul- 

 taneous with that of photography itself. Gutta-percha only just pre- 

 ceded the substance of which collodion is made ; the ether and chloro- 

 form, which are used in some methods, that of collodion. We say 

 nothing of the optical improvements previously contrived or adapted 

 for the purpose of the photograph : the achromatic lenses, which cor- 

 rect the discrepancy between the visual and chemical foci ; the double 



