THE YOUNG SCIENTIST. 
25 
faces. Now, the more acute the angles of the 
faces forming the wedge, the easier its edge 
will break off, abrade away, or bend over. 
Hence it is found best to make the top facet 
stand at an acute angle of about 4:° or 5°, or, in 
other words, at very nearly a right angle to the 
side face of the leg. 
We have now to consider a very important 
point in scissor grinding and sharpening. The 
distance of the scissor points from the joint 
which holds the legs together, renders very 
little pressure at the points sufficient to spring 
them apart, and slide past the work; hence the 
scissors may be tight enough at the joint to cut 
well near the joint, and yet not cut at the 
points, although the edge maybe equally sharp 
from end to end of the edge. To obviate this 
difficulty, and to cause the cutting edges to 
fairly meet, the side faces of each leg are 
curved in their lengths, so that when the legs 
are open and we look at them edgewise, they 
appear to cross each other; as a result the more 
we close them the more the edge of one is 
pressed to that of the other, and this compen- 
sates for the increased distance from the joint. 
Now if the joint of the scissors becomes loose, a 
pressure of the fingers must be relied upon to 
keep the edges in contact as the legs close. 
From these considerations we may perceive 
that, if, to sharpen a pair of scissors, we grind 
them on the side faces, we destroy or remove 
the bend in the length of the legs; hence the 
top or narrow faces only should be ground, 
unless, indeed, the legs are taken apart, and 
then we may grind the side faces, but even in 
that case it is not desirable to do so, because 
the proper amount of curve and twist upon 
those faces requires a good deal of experience 
to determine, and we are not likely to improve 
upon the practice and experience of the original 
manufacturer, who has made the matter a 
special study. Furthermore a very little error 
in grinding the surface of the joint will have 
considerable effect at the points, making them 
come together with too much or too little side 
pressure; hence it is always safer and better to 
grind the narrow faces only. A loose screw or 
rivet is a great defect in scissors, but if the 
joint is to be tightened by rivetting, the legs 
should be opened wide while using the ham- 
mer, otherwise the edges will be damaged at 
their point of contact. If the joint is a close 
fit, scissors may be sharpened to some extent 
by simply rubbing the narrow face or facet 
with a narrow surface of steel as the back of a 
knife blade, which will throw over a coarse 
wire edge. 
Some of my young friends may say, *' Does it 
require so many words to tell how to sharpen a 
pair of scissors ?" To such I answer, yes it 
does, if the learner is to have such a knowledge 
of the subject as to make him fed that he 
knows ^010, and not be liable to adopt some 
wrong plan, which somebody else may say will 
answer. There are right and wrong ways tO' 
do everything, and the only way to eliminate 
the wrong ways is to show the principles gov- 
erning the right ones. Then we shall know 
why as well as how the results are obtained, the 
zo/i?/ being almost or quite as important as the 
how. 
Mechanical Genius. 
I know at least a score of men who, though 
intelligent enough in other respects, do not 
know how to drive a nail in a workmanlike 
manner. As boys, they were educated with a 
view to practicing certain vocations or pro- 
fessions, and mechanical arts were completely 
ignored by their unwise parents or guardians.. 
Now, it is essential to every man — lawyer,, 
preacher, physician, merchant— to know som& 
of the principles of mechanical art, and how 
to apply them, for no one leads an industrious 
life without frequently seeing the use of such 
knowledge. There are certain mechanical 
rules that apply to almost every piece of work 
that man attempts to perform, from the folding 
of a paper to the matching together of twa 
boards, and the bungling manner in which 
these things are generally done, shows how 
little idea men have of mechanism. Then,, 
fathers, whether city men or country men, fit 
up a workshop for your boys. A small set of 
tools of the best material will not cost much — 
not more than ten or twelve dollars at most — 
and they will soon return you thrice their value 
in good accomplished. Where there is a com- 
fortable workshop, supplied with good tools,, 
the boys are seldom known to leave it upon 
leisure days to loaf in the streets. If nothing 
else is given them to do, they will be manufac- 
turing wind-mills, sleds, weather-cocks, hand- 
carts, etc. , and every hour thus employed adds 
to their skill as workmen. Very soon they will 
be able to make rainy days as profitable aa 
