106 PHILOSOPHICAL TRANSACTIONS. [ANNO 17Q7. 



ductor; so that an interrupted discharge only can pass through the tube, without 

 dispersing the whole of the water. But if the discharge be not seemingly as strong 

 as the tube can bear without breaking, the gaz is not produced from it; and on 

 this point hinges this extremely delicate process. The situation of the different 

 parts of the apparatus for the interrupted discharge is shown by pi. 2, fig. 12. 



To succeed by the method of the complete or uninterrupted discharge, the appa- 

 ratus now to be described must be used, and the following rules must be observed. 

 1. A tube, fig. 13, is employed, about 4 or 5 inches in length, and its bore J- or -£- 

 of an inch in diameter. One end is mounted with a brass tube, fig. 14, and the 

 other end is sealed at the lamp with a wire, about ■ ? V°f an mcn lu thickness, fitted 

 into it, as above described; which extends into the brass tube, so as to be almost 

 in contact where the explosion is made. If the wire touches the brass tube, 

 there will be no gaz produced. The tube being filled with water, and set in 

 a cup of water, the discharge may be made into it, as in the above described pro- 

 cess of Mr. Van Troostwyk; but here the insulated ball must be placed at a 

 greater distance from the prime conductor, and a Leyden jar with only 50 square 

 inches of coating will answer the purpose. In this way of making the experiment 

 gaz is produced by each discharge, in the brass tube; and in much greater quan- 

 tity, and with much less frequent accidents, and less trouble, than in the former 

 method with the interrupted discharge. But the gaz obtained with this apparatus 

 always contains a large proportion of atmospherical air, on account of the quantity 

 of water, and more immediate and extensive communication of it with the atmos- 

 phere. By repeated discharges there is an impression made in the brass tube, in 

 the part where the discharge passes through it, and at last a small hole is made in 

 that part. On this account the same mounted tube cannot serve for producing a 

 large quantity of gaz. 



2. The other sort of apparatus, invented by Mr. Cuthbertson, is represented by 

 fig. 15. At first it consisted of a glass tube 4- an inch wide, and about 5 inches in 

 length, mounted at 1 end with a brass funnel, and inverted in a brass dish; but 

 afterwards the tube was blown funnel-wise at the end, as shown by fig. l6. The 

 other end must have a wire, about ^V of an inch thick, sealed into it at the lamp; 

 which wire extends to nearly the bottom of the brass dish in which the tube stands. 

 The exact distance between the end of the wire and brass dish must be found by 

 trials; that which generally answered in my experiment was about -^ of an inch. 

 If it be properly arranged, gaz will be produced at each discharge. The Leyden 

 jar used with this apparatus, must contain above 150 square inches of coating. 

 The distance between the insulated ball and the prime conductor, at which the ex- 

 periment succeeded, was commonly about 4- an inch. If experiments be proposed 

 in which electric discharges must be passed through water, or other fluids, for even 

 a much longer time than was consumed in performing those referred to, or related 

 in this paper; it may be an object to employ the wind, or perhaps the power of a 

 horse, to turn the electrical machines; the? expence of labourers being considerable. 



