76 Proceedings of the Asiatic Society. | Maron, 
greater sensitiveness of the instrument would only complicate the 
method. 
As it is intended that the tester himself should turn the handle 
of the magneto-electric machine, he has it entirely in his power to 
regulate the strength of the induction currents by turning faster 
or slower, and as, besides this, he always begins the testing by at 
first sending the currents through his fingers, no severe shocks can 
occur to him in the subsequent operation. 
The method has also a safeguard in itself against carelessly 
rejecting good insulators, because the tester will certainly be 
careful in having the insulator properly cleaned before testing it, 
in order to avoid severe shocks. 
There can also be scarcely any doubt that the tongue is the 
best detector in this particular case, because it is sufficiently 
sensitive, never comes out of order and indicates almost momen- 
tary currents ; it is besides the cheapest instrument that could be 
used. 
[Note]. This method may also with advantage be used for 
detecting bad joints in a telegraph line. It is then only necessary 
to connect the two ends of the joint to the two terminals of the 
magnetoelectric machine, in such a way that the body of the tester 
acts as a shunt to the joint. 
A joint which offers a resistance of not less than 5 8. U. allows 
a current to pass sufficiently strong to be detected by the tongue ; 
but if the joint has a resistance of more than 2008S. U. the cur- 
rent passing is strong enough to be felt already by the fingers of 
the tester. 
Mr. W. E. Ayrton observed, that there is one point of excellency 
in Mr. Schwendler’s arrangement for detecting bad insulators 
which, as Mr. Schwendler has not mentioned it, he should like to 
say a few words about. Testing insulators by passing a current 
through them is not new, but the current used for this purpose has 
up to the present time been that obtained from a galvanic battery, 
and to observe such a current a most delicate galvanometer is re- 
quired. Now both a galvanic battery and a delicate galvanometer 
are in themselves most unportable, the battery because it must be 
