196 Mr. Armstrong's Account of a 



The peculiar shape of this aperture appears to derive its effi- 

 cacy from the tendency it gives the steam to spread out in the 

 form of a cup on entering the wooden pipe; and by that means 

 to bring it, and the particles of water of which it is the carrier, 

 into very forcible collision with the rubbing surface of the wood. 

 This explanation is not mere conjecture, for I find that when 

 water is forced with a strong pressure through a similar aper- 

 ture, it is dished out in the manner shown in fig. 2. 



The steam is discharged against a range of Fig- 2- 

 metallic points communicating with the ground, \ 

 by which its electricity is carried off and so pre- \ 

 vented from retroceding to the boiler. These 

 points are placed very near to the jets, in expe- 

 riments which require a large quantity of elec- 

 tricity, without great length of spark; but when 

 high tension is an object, they are removed to a 

 distance of three or four feet from the dischar- 

 ging apertures. 



As an example of the power of this machine 

 in charging jars, I may state that my friend Captain Ibbetson, 

 one of the Directors of the Polytechnic Institution, who lately 

 visited me for the purpose of seeing the machine, and who has 

 co-operated with me in most of the experiments made with it, 

 brought with him from London a large Leyden jar, which 

 had discharged spontaneously fifty times in a minute when 

 tried with the colossal plate machine belonging to the Institu- 

 tion ; and that when this jar was applied to the boiler, it gave 

 140 similar discharges in the like space of time. 



The spark which the boiler produces, although occasionally 

 reaching twenty-two inches in length, is by no means com- 

 mensurate with its other effects. 



Its greatest power is manifested when the electricity is 

 drawn off merely as a current, without any disruptive dis- 

 charge; and the results I have obtained, when using it in 

 this way, will, I conceive, prove highly interesting to you. 



The true polar electro-chemical decomposition of water, 

 which has never hitherto been unequivocally performed by 

 frictional electricity, has been effected in the clearest and most 

 decisive manner by means of this machine ; and I shall now 

 describe an experiment in which this interesting effect was 

 combined with other curious phaenomena. 



Ten small wine-glasses were arranged as shown in fig. 3, 

 and into each glass was poured an equal measure of the 

 liquid named opposite to the glass containing it. A glass 

 tube, closed at one end around a platina wire, which extended 

 an inch and a quarter into the tube, was then inverted in each 



