May 25, 1882] 



NATURE 



85 



succeed in obtaining the various positions of the wings of 

 a bird at each revolution. As the result of a good deal 

 of thought and labour, an apparatus was constructed about 

 the size of a sporting-piece (Fig - 1), which would take 



twelve images, in one second, of an object on which the 

 piece was continuously sighted. The time of exposure of 

 each image was about 1 -720th of a second. 

 The barrel of the gun is a tube containing a photo- 



Fig. 2. — Mechanism of Gun. i, Ge.-.eral view ; 2, Windowed disc ; 3, Box with 25 stnsitive plates. 



graphic object-glass. Behind this, and solidly mounted work is set in action, giving to the different parts 

 on the butt, is a long cylindrical breach, containing clock- of the instrument the necessary motion. A central axis, 



which makes twelve revolutions per second, governs 

 all the pieces of the apparatus. Of these one is a disk of 

 metal pierced with fine openings, which acts as a dia- 

 phragm, and only allows the image of the object to be 

 presented twelve times in a second, and each time only 



vhich the exterior of the barrel is seen at r:, 

 t. On pressirg the triggT the clock- 



Fig. 4— ing i»f depression of wine. 



for i-720th of a second. Behind this, and revolving on 

 the same axis, is another disk carrying twelve windows, 

 behind which ;ire the sensitised plates. This windowed 

 disk revolves in such a way as to be slightly arrested in 

 its course twelve times in a second, when the open win- 

 dows are exposed to the light. The teeth to arrest its 

 movements are seen at c, Fig. 2, No. 2, while the ex- 

 centric at f. Fif;. 2, No. 3. ke«"ps up the regul irity of this 



