Jor detecting Metallic Masses in the Human Body. 48 - 
fig. 5) was rattling against its contact pieces, thus producing an 
impure sound, and I could distinguish among the upper-par- 
tials the tone that had been reinforced by the condenser. 
ound, upon connecting them with the coils E F, as shown in 
fig. 17, and, holding a leaden bullet near the coils, that each 
be heard continuously, like the drone of the bag-pipe, while 
oe higher tone changed its pitch with each change of con- 
enser, 
The pitch of the high tone reinforced seemed to depend upon the 
electro-static capacity of the condenser employed, but the exact 
relation between the two has not been ascertained. In experi- 
ments 5, 6, 7, 8, and the subsequent experiments described 
above, the battery em loyed consisted of six pairs of carbon 
and zine plates of large area placed in a solution of bichromate 
of potash containing sulphuric acid. 
e effects noted above were not produced satisfactorily 
when the battery was much run down, nor were they obtained 
with a Leclanché battery which had been set up for some time, 
but which appeared to be in good condition. aS 
At is evidently necessary in order to produce this characteristic 
high tone to use a battery possessing considerable electromotive force 
and shght internal resistance. 
ur experiments had reached this stage when, on Saturday, 
the 20th of J uly, 1881, I was requested to make another trial 
— we person of the President at the evening dressing of the 
ound. 
At this time, however, we had no exploring instruments 
Completed excepting one or two like that shown in fig. 11; for 
't will be understood that the promising results noted above 
