3Q4: On the Formation of JVater by Compression. 



engage it by a compression much less rapid. We are thus 

 led to see in the electric spark a result purely mechanical. 



If we now compare what takes place in the compressing- 

 pump and Voita's eudiometer, the analogy is complete : 

 only in the first case we are obliged to confine the air, be- 

 cause the velocity which we can give to the piston is li- 

 mited ; whereas in employing electricity the particles are 

 compressed with a velocity so great, that they can never 

 recede with so much speed as to withdraw themselves from 

 its effort. The compression then, and also the disengage- 

 ment of light, or the spark, which is the consequence of it, 

 may take place as well in the open air. But this effect is 

 local ; and if the gases, not being susceptible of combining, 

 should return, after each explosion, to their primitive di- 

 mensions, they would immediately resume in that state of 

 dilatation all the heat at first disengaged from them, so that 

 no lasting change could be effected in their constitution : 

 and this serves to explain why no alteration has been ob- 

 served in pure and unmixed gases when subjected to the 

 action of the electric spark. 



This light which electricity disengages from gases by 

 compression would still be disengaged from those most ra- 

 refied, and in consequence of its extreme velocity it ought 

 to disengage it even from vapours, if the experiment were 

 made under a receiver or in the Torricellian vacuum; for we 

 can never form a perfect vacuum with our machines, and 

 even in the barometric tube there is always mercury in 9 

 state of vapour. This vapour, though highly rarefied, still 

 contains a ver)' large quantity of caloric, which electricity 

 in its passage ought to disengage by compression ; but the 

 instantaneous increase of elasticity which thence results 

 cannot become sensible, on account of the little density of 

 the medium ; whereas it becomes sensible in denser air, as 

 seen in that instrument called Kinnersley's thermometer. 



These considerations seem to me to indicate that the 

 phasnonienon called the electric spark arises from the licrht 

 disengaged from the air by compression during the passage 

 of electricity ; so that this phaenomenon is merely mecha- 

 nical, and has nothing in it electric. Such is tire idea 

 which I submit to philosophers. If true, it tends to dimi- 

 nish considerably the number of the hypotheses already 

 formed, and which might be formed on the nature of elec- 

 tricity. For this reason I thought it my duty to present it 

 to tlieir reflections; but I beg them to be persuaded that I 

 shall attach no more importance to it than what they them- 

 selves shall give to it. 



LXII. Ao- 



