on Electric discharges through Water . 145 
water and of air. It must be added, that although water in large 
quantity is a good conductor, and air is not, yet water being 
here in very small quantity it proves a bad conductor; as is the 
case with the very best conductors. A cubic foot of water is 
only just capable of receiving, or letting pass through it, a 
full discharge from a jar of one foot of coated surface ; and the 
quantity of water employed in this experiment not being 
part of a cubic foot it is a very imperfect conductor; 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 ex- 
tremely delicate process. 
The situation of the different parts of the apparatus for the 
interrupted discharge is shewn by Tab. III. fig. 5. 
To succeed by the method of the complete or uninterrupted 
discharge , the apparatus now to be described must be used, and 
the following rules must be observed. 
1. A tube, fig. 6. is employed, about four or five inches in length, 
and its bore one-fifth or one-sixth of an inch in diameter. One 
end is mounted with a brass tube, fig. 7. and the other end is 
sealed at the lamp with a wire, about of an inch in thick- 
ness, fixed 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 de- 
scribed process of Mr. van Troostwyk; but here the insulated 
ball must be placed at a greater distance from the prime con- 
ductor, and a Leyden jar with only fifty square inches of coating 
MDCCXCVII. U 
