644 EEPORT — 1892. 



of the strip, the latter was clamped at different distances from the end, and this 

 was found to make no difference in the time which elapsed between each attrac- 

 tion as long as the discharging circuit was not altered. When, however, the 

 resistance was increased without correspondingly increasing the self-induction, the 

 time between successive attractions was diminished. In order to obtain a perma- 

 nent record of these attractions, the end of the strip was placed in contact with 

 sooted paper, which revolved uniformly on a small roller rotating about a vertical 

 axis. The results obtained showed usually three attractions, and showed very 

 clearly the effect of including more resistance and more self-induction, with 

 one or both coils of electro-magnet. This method, however, did not demonstrate 

 that there was actually a reversal in the current at each semi-oscillation, and 

 therefore it was abandoned. The recording apparatus of a siphon-recorder was 

 then used, but it was found to be too delicate for the rough apparatus employed. 

 Ultimately a long thin permanent magnet was fixed so as to vibrate, with one end 

 over a pole of the electro-magnet. By this both an attraction and repulsion could 

 be registered. _ The tracings shown give the compound harmonic motions made up 

 of the free vibrations of the permanent magnet and of the oscillations. The 

 different tracings show the effect of having both coils in the circuit and of in- 

 cluding extra coils, some being wound non-inductively and some inductively. 

 The free vibration of the magnet is also shown. The charging potential was about 

 no volts. _ This method and the curves are, of course, not intended to be used for 

 quantitative purposes, but are given simply as a verification of the theory of the 

 oscillatory discharge, and as of interest on account of the oscillations being so 

 elow. 



6. Inducto-Script. By Rev. Frederick J. Smith, M.A. 



The well-known breath figures of Moser, Eiess, and Karsten suggested to the 

 author the idea of producing similar figures on photographic plates; in 1878 an 

 experinient to determine the action of a discharge from a coin on to a photo-plate 

 wa8_ tried. The image was produced on development, but very imperfectly. 

 During the last two years an inductorium or transformer has been under constant 

 trial. It occurred to the author that probably its high potential might be used to 

 produce figures similar to those of Karsten : plates of glass were cleaned with care, 

 and operated on in the way suggested by Karsten, but no results were to be got 

 out of it ; probably the potential difference was not great enough. 



A photo-plate was used in the place of the glass, and on development the 

 exact pattern of the medal used was produced; this showed that a potential 

 difference, greatly under that of a jar discharge, or that of an electrical machine, 

 would upset the chemical equilibrium of the photo-plate. Several factors appeared 

 to be_ contributing to the result— the potential difference, the gas in which the 

 experiment was performed, the pressure under which the experiment was done, 

 the temperature, and the history of the plate previous to the experiment. 



It is to be noticed in reading the work on breath figures by Grove and Karsten 

 that Grove tried to set the image by coating an electrised plate with collodion and 

 nitrate of silver, and then developed out the word Volta (Grove, ' Correlation of 

 Physical Forces,' 1870, p. 404, § 4). He did not let the electrical discharge to act 

 on the silver salt. Again, Karsten did not succeed in producing a fixed picture on 

 a daguerreotype plate. He writes : ' If an iodised plate is taken, and a picture 

 produced thereon, the vapour of mercury will not bring it out, although the image 

 IS really on the plate, as may be shown by breathing upon it.' Moser appears to 

 have got out pictures by means of water vapour, but they were not permanent 

 effects. 



Summary of results : — 



I. The different gases used were oxygen, carbonic acid gas, air, coal-gas. Far 

 the best results were obtained in oxygen. Experiments with other gases are now 

 being made. 



II. The effect of pressure. No picture could be obtained in a good vacuum, 



