112 Notice of some New Electrical Instruments. 
beautiful illumination. After repeating it several times with this im- 
age, I prepared some pieces of a larger size by stripping off the rind — 
carefully and drying them thoroughly. The effect of passing a spark 
through pieces six and eight inches long was truly beautiful. A 
splendid yellow light is produced, unlike any thing which I have ever 
seen in electrical illuminations., I have used always the same pieces 
which I prepared three years ago, and they still answer perfectly 
well; but as they absorb moisture so readily they must always be 
dried previous to use. I have lately prepared some pieces, and after 
drying them thoroughly, enclosed them in a glass tube secured at 
both ends by a plug of sealing wax. At each end of the pith a me- 
tallic button is fixed, connected with a wire which passes through 
the wax and terminating in the brass knob which is to receive the 
spark. 
The following experiment also may be not entirely without use. I 
found that if a glass tube be coated with gum copal varnish its elec- 
tric power is increased ina remarkable manner. When the varnish 
is very dry and smooth, if the tube be rubbed with amalgamated silk 
it throws off at each stroke long brushes and sparks. It occur- 
red to me to varnish the cylinder of my machine. [I tried the ex- 
periment several times and failed. These failures were owing prob- 
ably to my impatience, in not suffering the varnish to harden suffi- 
ciently. This winter I was determined to give it a fair trial, and E 
have been amply repaid for a little patience. The result of the trial 
far exceeds my expectations. ‘The machine works with astonishing 
power. In tolerable weather an eleven inch cylinder causes a ball of 
an inch and a half to act like a point. ‘The varnish should be very 
smooth, and previous to use, it should be polished by turning the cyl- 
inder against a piece of soft silk. ‘The rubber should be free from 
any projections which might scratch the varnish. The amalgam 
should be very soft and free from grit. ‘There is one inconvenience 
attending this experiment, that is the necessity of cleaning the cylin- 
der very often. If this could be obviated, the improvement would be 
complete. 
Salem, Mass. March 4th, 1833. © 
