146 Dr. Pearson’s Experiments and Observations 
will answer the purpose. In this way of making the experi- 
ment gaz is produced by each discharge, in the brass tube; and 
in much greater quantity, and with much less frequent acci- 
dents, and less trouble, than in the former method with the 
interrupted discharge. But the gaz obtained with this appa- 
ratus 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 atmosphere. By re- 
peated 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. Cuthbert- 
son, is represented by fig. 8. At first it consisted of a glass tube 
half an inch wide, and about five inches in length, mounted at 
one end with a brass funnel, and inverted in a brass dish ; 
but afterwards the tube was blown funnel-wise at the end, as 
shewn by fig. 9. The other end must have a wire, about ^ 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 experiments 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 
about 150 square inches of coating. 
The distance between the insulated ball and the prime con- 
ductor, at which the experiment succeeded, was commonly 
about half an inch. 
If experiments be proposed, in which electric discharges must 
