332 Cutbush on the Voltace Lamp. 
but, should there be an unusual consumption of gas, it may 
be supplied by suspending a bar of zinc in the vessel G. 
the lower end of which should reach only one third below 
the brim of the vessel ; the reason for which will be obvious 
to those who understand the structure of the instrument. 
The stop cock at C. is for drawing off the acidulated water, 
when it becomes saturated with the zine. 
The calorimoter which I use differs a litile in construe- 
tion from those commonly made, and perhaps has some ad- 
vantages. The following is a description of it: Take a 
sheet of copper, say four inches wide, and eighteen or twen- 
ty inches long; bend it in the form represented in Fig. 2. 
(see the plate at the end of the volume,) which is preserved 
in the required shape by a band of the same metal sur- 
rounding it; the intervals between each fold should be 
about an inch; then cast in proper moulds plates of zine, of 
different sizes, so as to slide between these interstices, 
reaching from the bottom to the top, the edges of which 
should be grooved into little strips of wood, in order to pre- 
vent contact with the copper ; all these plates of zinc should 
be connected together by a strip of copper along their up- _ 
per edges. By this construction these plates can be easily 
removed, and cleaned whenever required. With an in- 
strument of the above dimensions, I have melted off fine 
iron wire. 
Arr. XX. Account of an improvement in the Electrical 
Lamp, by Dr. James Cursusn, of Philadelphia, in a 
letter to the Editor. 
TO PROFESSOR SILLIMAN. 
Puintapetruia, March 15, 1820. 
Sir, 
Some years ago, I purchased an inflammable air lamp, 
commonly called the Voltaic Lamp, made on the original 
eonstruction, which I laid by, as not only troublesome to 
use, but very uncertain in its operation. A description of 
the apparatus with its appendages, may be seen in Adams’ 
