Obfervations on Electricity* 271 
gam on the (ilk, produced by applying the leather to the cylin- 
der in one diredion of turning, was the reverfe of what mu ft 
take place when the contrary operation was performed, 
Notwithftanding all this, as the intenfity with the two 
cufiiions was fuch as moft operators would have called ftrong, 
the method may be of ufe, and I ftill mean to make more 
experiments when I get poffeffion of a very large machine 
which is now in hand. 
iy. The more immediate advantage of this difcovery is, that 
it fuggefted the idea of two fixed cufiiions with a moveable 
filk flap and rubber. Upon this principle, which is fo Ample 
and obvious, that it is wonderful it fhould have been fo long 
overlooked, 1 have conftruded a machine with one condudor, in 
which the two oppofite and equal ftates are produced by the 
Ample procefs of loofening the leather rubber, and letting it 
pafs round with the cylinder (to which it adheres) until it 
arrives at the oppofite fide, where it is again fattened. A wifh 
to avoid prolixity prevents my defcribing the mechanifm bjr 
which it is let go, and fattened in an inftant, at the fame time 
that the cufhion is made either to prefs or is withdrawn, as 
occafion requires. 
20. Although the foregoing feries of experiments naturally 
lead us to confider the filk as the chief agent in excitation ; yet 
as this bufinefs was originally performed by a cufhion only, it 
becomes an objed of enquiry to determine what happens in 
this cafe. 
21. The great Beccaria * inferred, that in a Ample 
cufhion, the line of fire, which is feen at the extremity of con- 
tad from which the furface of the glafs recedes, confifts of 
returning eledricity ; and Dr. Nooth grounded his happy 
* Philofophical Tranfaftions, Vol. LVI, p. 117. 
Rr 2 
invention 
