PHOTOGRAPHING THE FLIGHT OF INSECTS. 



Bv DR. ALFRED GR.\Di:X\VITZ. 



Apart from its spectacular interest and educational 

 value, the cinematograph is a most useful apparatus 

 for scientific investigation, allowing such phenomena 

 as are too rapid or too slow for direct visual inspec- 

 tion to be decomposed into their various phases. 



A French scientific man, Lucien Bull, of Paris has 

 developed a most ingenious method which greatly 

 increases the scope of the cinematograph bv aug- 

 menting its speed — that is, the number of pictures 

 taken within a second — to almost incredible figures. 



- .^ z 



FlGU 



Figure 1. 



\Miereas the ordinar\- apparatus takes from thirty to 

 fiftv instantaneous pictures during a second, this 

 high-speed cinematograph, in fact, enables as many 

 as two thousand views to be taken during this short 

 interval. It is thus possible to decompose the most 

 fugitive phenomena, such as the motion of insect 

 wings, as far as 

 can be desired, 

 and by project- 

 ing the compon- 

 ent pictures on 

 a screen in more 

 or less rapid 

 succession, to 

 study their very 

 mechanism. It 



mav be said that by investigating the flight of insects, 

 it is hoped to arrive at a true understanding of many 

 problems met with in aviation. 



It will be readilv understood that no mechanical 

 apparatus is able to open and close the shutter of a 

 photographic camera two thousand times a second. 

 Moreover, the ordinary illuminants 

 are far from possessing the inten- 

 sitv required for producing an 

 efiicient impression on the photo- 

 graphic plate or film during so 

 infinitely short an inter\al. 



The inventor therefore avails 

 himself of the electric spark, which 

 unites two extremely valuable 

 properties, viz., an instantaneous 

 duration, and enormous photographic efficiency. 



His apparatus (Figure 6) consists mainly of a paste- 

 board roll bearing on its circumference a photographic 



film, and which, under the action of an electric motor, 

 rotates extremely rapidly. 



A rotary interrupter mounted on the axis of this 

 roll breaks the primary circuit of an induction coil a 

 certain number of times during each rotation, and 

 each break produces an induction spark behind an 

 optical svstem used for concentrating the beam of 

 light on the objective. 



After starting the apparatus, the sparks are seen 

 to pass the more rapidly as the speed of rotation of 

 the roller is higher. Each spark 

 will produce a photographic picture 

 on the portion of the film which 

 happens to be in front of the objec- 

 tive. In order therefore to obtain 

 on the film a series of images of 

 an object situated in front of the 

 optical svstem, the objective should 

 ' be kept open during the time of 



one rotation of the roll. 

 The roll used bv Lucien Bull is about one foot in 

 diameter, and accordingly can receive a film about 

 three feet in length, containing fifty-four photograplis 

 of the same size as ordinary- cinematograph pictures. 

 In order to allow the apparatus to be operated in 

 full davlight the rotating roll is enclosed in an 



box, 

 upper half 



octagonal 



r4 



r-*- 



the 



of which can be 

 removed for the 

 sake of insert- 

 ing the film. 

 The objective is 

 contained in a 

 small wooden 

 compartment or 

 pointer at the front of the box. and which contains 

 a mirror reflecting the image of the object on to the 

 ground glass window, thus allowing the apparatus to 

 be accurately adjusted. Before beginning the 

 experiment, this mirror is fitted so as to leave 

 free the wa\- to the objective, and to provide a 



Figure 3. 



light-tight 



closure for the sighting window. 

 The proper speed of rotation is best ascertained by 

 gauging the sound given out by the sparks, which is 



343 



