74 
THE YOUNG SCIENTIST. 
kerfs are parallel with the edges of the 
box ; this is the neatest way to put iii the 
strips, and is as strong as any other when 
the work is neatly done, but sometimes 
workmen run in the kerfs on an angle, 
which, to say the least of it, is reprehen- 
sible, as the work, when varnished or 
polished, does not look so well, and is 
certainly not any stronger tiian when the 
strips are put in parallel with the edges. 
Easy Experiments in Electricity. 
HEN I first took an interest in 
the study of Natural Pliilos- 
oi)hy, I wanted to try some ex- 
l)eriments illustrating the dif- 
ferent phenomena of electricity, but I 
could find no simple directions for per- 
forming them without considerable ex- 
pense. The object of these articles is to 
help others in like circumstances to get 
the same enjoyment and instruction, and 
save their niouey for other purposes. 
On page 2, Vol. V, of the Young Scien- 
tist, are directions for obtaining a spark 
a clothes-brush ; then lay it on the tray, 
hold your knuckle near it, and you will 
get a spark of negative electricity. Now 
lift the paper and hold your knuckle near 
the tray, and you will get another spark, 
but of positive electricity. I have ob- 
tained sparks in this way one and one 
half inches long, when the conditions 
were favorable. 
To give a sensible shock we must have 
a condenser, either a Leyden jar or the 
following apparatus, which, though it 
costs almost nothing, is quite effective. 
Take two pieces of sheet tin, 8x10 inches, 
or larger, and sec them on a glass goblet, 
with a piece of window-glass, a little larger 
than the tins, between them. Now take a 
piece of brown paper, warm it, and rub it, 
as in the electrophorus, lay it on the 
upper tin, and touch the latter ; then 
raise the paper and touch the under tin, 
repeat the operation several times, and 
then, by touching the under tin with one 
hand and the upper tin with the other, 
you will receive quite a shock. 
The explanation of this is, that when 
^^^^^M ^^^^^^ ^ ^ 
m 
from a piece of brown paper and a bunch [ the paper is rubbed it is charged with 
of keys, but you may get a longer spark negative electricity ; laying it on the tin, 
with the following simple apparatus, the negative electricity in the paper a1- 
wliich we call the " tea-tray electropho- • tracts the positive in the tin, and theneg- 
rus." This consists of an ordinary me- 1 ative flows off through the hand to the 
tallic tea-tray, supported by two glass gob- ground. Then, when the paper is lifted, 
lets and a piece of brown paper, the same | the positive electricity in the upper tin, 
size as the inside of the tray, with a small being free, attracts the negative in the 
strip of paper fastened to each end for imder tin. By touching it the positive 
handles. To obtain a spark, first heat ' flow^s off to the ground, leaving the under 
the paper pretty hot, and rub it well with , tin charged with negative and the upper 
