Woter hy the EkcJric Explofion. J43 



from one another. If they be too near one another, the points of them will not be illuminated ; 

 and provided the infulated ball be as near to the prime condu£lor as the two wires are to 

 one another, the tube will be broken, becaiife there will be a complete explofion. . But 

 if the wires be at too great a diltance from one another, the eleflric fluid of the difcharge 

 will be fo diffufed through the water that no gaz will be procfuced. If the Leyden jar con- 

 tain, as above ftated, 150 01 160 fqiiare inches of coated furface ; and the ball of the prime 

 I conduftor and of the infulated ball be about three inches in diameter, the dillance between 

 tlie wires which generally anfvvercd bed, was about c-Sths or y-Sths of an inch, as above 

 faid. The narrower the bore of the tute, the greater may be the diflance between the two 

 wires; accordingly, the dillance may be one inch with a tube i-]4th of an inch wide. 



5. The uf'per ivire fixed into the clofeil extremity of the tubes muf^be of a proper length and 

 ibicknefs. If this wire be too long, either the difcharge will not be carried through to 

 the end of the lower wire in fufficient quantity to produce gaz ; or, if it be in fufFicient 

 quantity to produce gaz, the tube will be fraftured. The fmaller the diameter of the tube, 

 the longer may be the upper wire, for a reafon to be-given under the next head. I generally 

 found that the difcharge requifite to produce gaz fractured the tube, if the upper wire was 

 more than 6-8ths or 7-8tlis of an inch in length, within a tube of more than i-Sth of an 

 inch in diameter. But with very narrow tubes, fuch as thofe of i-i6th of an inch in dia- 

 meter, I frequently fucceeded when the upper wire was i^th of ati inch in length. It is 

 obvious, that the fliorter the upper wire the more readily will gaz be produced: the procefs, 

 however, will be rendered dill more tedious in thofe cafes in which a quantity ofgaz is to 

 be colleifled in a refer\'oir for exammatron; on account of tlie time confumed in transferring 

 fuch fmall parcels of gaz by each experiment. 



The diameter of the upper wire cannot, perhaps, be too fmall ; for the greater its fuper- 

 ficies, the more eleftvic fluid will be parted with to the furrounding water. Hence placina 

 wire of the fineft fort, as that of i -240th of an inch in diameter, may be ufcd with fuperior 

 advantages. This fort; of wire alfo cannot be melted while it is foldering to the glafs, 

 which can hardly be prevented with fine wire of other metals. However, I found that 

 copper, brafs, or gilt wire, of about i-8cth or i-lcothof an inch in diameter, could be 

 foldercd to the glnfs, and anfwered perfe£lly. I did not find that any of the metal wires 

 were aflccled by the difcharge ; but iron or fteel ones are not proper, on account of their 

 being fo foon oxidificd by the water, and confequently extricating from it hydrogen gaz. I 

 did not find any advantage from ufing feveral fmall wires twilled together, but feparated at 

 the end within the tube; for gaz was extricated generally, at the point of one of theni only, 

 namely, ihe undcrmofl. I think care fliould be taken to fix the upper wire fo that it fliall 

 be in the middle of tlic tube; as in that cafe the tube will be lefs liable to be broken. As to 

 the under wire, the diameter of it feenis to be of little importance; for, if it be a thick one, 

 as much gaz will be extricated as if it were a fmall one ; becaufe the cledlric difcharge will 

 tjkc the firll point of the furface of the wire where the gaz is produced. 



6' The tubes miijl be of a proper length and diameter. If they be fliorter than fcven inches, 

 tlic difcharge will be liable to pafs over the outfide ; and if they be longer than twelve 

 inclics, they will be of an inconvenient length. I found tlie mod convenient length to be 

 from nine to ten inches, cxclufive of the curved part. Tlie curved part was found very 

 ufcful in preventing air afccnding, which was accidentally kt into the tube, by which the 



pioduct 



