306 Mr Aston, Neon Lamj)s for Sirohoscopic Work 



total duration of the flash. In neither case was the fuzziness of the 

 image of a measurable order. After careful observation under 

 good conditions the conclusion of three observers was, that it was 

 probably less than one-tenth of a division and certainly less than 

 one-fifth. This gives the maximum duration of the working flash 

 as one-ten-millionth of a second, so that it can be taken as perfectly 

 instantaneous for the purpose employed. 



Other Technical Afflications . 



Of the many uses besides measuring velocity of rotation to 

 which Neon lamps may be put with advantage in engineering and 

 other problems it is sufficient to mention two in which they have 

 been very successful. Any rapidly rotating mechanism such as an 

 airscrew, if illuminated by a lamp the break of which is operated 

 mechanically at each revolution, will appear at rest, flicker being 

 small at speeds well over 1000 r.p.m., so that strains or movement 

 of parts can be examined with great accuracy under actual working 

 conditions. 



A still more striking effect can be obtained by illuminating a 

 high speed internal combustion engine by a lamp whose break is 

 operated mechanically at e.g. 99 breaks per 100 revolutions of the 

 engine shaft by the use of a creeping gear. The engine then appears 

 to be rotating quite smoothly at one-hundredth its normal speed 

 so that such instructive details as the movements of the valves 

 and springs, the bouncing of the former on their seats, etc., can be 

 studied with ease. 



It is of course necessary for the speed of rotation to be fairly 

 rapid to give appearance of continuity to the eye and in conse- 

 quence one cannot apply this method to the analysis of such a 

 thing as the movement of a chronometer escapement. 



As the technical importance of Neon lamps is rapidly on the 

 increase it is very desirable that liquid air engineers in this country 

 should consider the erection of a fractionating plant for recovering 

 the gas from the air (which contains -00123 per cent, by volume) 

 such as has been used with such success by Mons. Georges Claude 

 of Paris, to whom the author is indebted for the Neon with which 

 these experiments were performed. 



