THE YOUNG 
SCIENTIST. 
Information Wanted. 
1. Ed. Young Scientist— Youv prospectus hav- 
ing fallen into my hands, I see that you pro- 
pose to bring your subscribers into communi- 
cation with each other. I am very glad of this, 
for I find that when I write to make an inquiry 
of some papers, the editors just turn to some 
old receipt book and copy out of that, and ten 
to one the thing will not work, for, like the" 
razors Peter Pindar tells us about, too many of 
the recipes that we find in " encyclopfedias," 
and "dictionaries of recipes," were made to 
sell and not to be put in practice. A better 
plan is that which you have adopted, which is 
to open an exchange for the barter of ideas, for 
as some one says, "Everj'^body knows more 
than anybody." 
So much by way of preface. Can any of your 
readers give me a really good method for 
"eboniziag" wood? I have several recipes, 
but none of them give good results. A recipe 
recently published in a prominent journal 
would not work at all. Amateub. 
2. Ed. Young Scientist Seeing by the circular 
announciug your journal, that you propose to 
insert letters from subscribers who desire infor- 
mation, I would ask if any of your readers can 
tell me how to repolish the brasswork of a tele- 
scope that has been in use for some time, and 
has become quite tarnished? I have used very 
fine polishing powders, but although this an- 
swers well for a few days, in a short time the 
instrument looks worse than ever. 
KUSTYCUSS. 
[Specially written for the Young Scientist.] 
The Art of Sharpening Edge Tools. 
By Joshua Eose, M. E. 
NO. I. 
There is an adage which tells us that " a good 
workman never quarrels with his tools." And 
this is too often supposed to mean that we can 
make up for a defect in a tool by the employ- 
ment of a little extra skill and care in its 
handling. A more correct interpretation, how- 
ever, seems to be that a good workman so 
shapes and sharpens his tools that there is no 
need to quarrel with them, for in a tool made 
for any purpose there can be no fault that does 
not lie at the door of its maker or user, and we 
shall find that with tools, as with everything 
else, they are good servants in proportion as 
they are properly cared for and used. 
The construction of every tool that the human 
hand can use is governed, both as to shape, 
strength, and the form of its cutting edge, by 
principles easily applied when properly under- 
stood, and to explain in a simple manner these 
principles and their application will be the 
object of these articles. 
Beginning, then, with the common penknife, 
we have a tool which may be used either to 
cut, split or scrape; but since its duty is mainly 
that of cutting, its edge should be formed with 
a view to that end, thus fitting it to the largest 
class of work. This will, fortunately, not in- 
capacitate it for the performance of its lesser 
fields of usefulness. 
The shape of a penknife blade is in section 
that of a wedge, and the sharpness or keenness 
of its cutting edge depends upon the acuteness 
of the wedge, and upon how nearly we can 
make the two sides or facets at the thin end of 
the wedge meet, without either facet turning 
over towards the other at the extreme edge, 
and how smooth and even we can leave the 
facets at the edge. The difficulty experienced 
in accomplishing this is due to the weakness of 
the metal, which causes it to bend over and 
away from the surface applied to the instrumeut 
used for sharpening or abrading it. The acute- 
ness of the wedge, in a new knife, is fixed by 
the manufacturer; hence we need not at present 
discuss it, but may pass at once to the sharp- 
ening processes. 
If we grind a knife blade upon a grindstone, 
and then put it under a microscope, we shall 
find that it appears as shown in Fig. 1. The 
marks shown .upon the facet are due to the 
fact that the cutting or abrasion performed by 
the grindstone or emery wheel, is done by the 
corners or angles of the grains of emery or 
stone, as the case may be, and it follows that 
the coarser those grains, and the harder the 
blade is pressed to the stone or wheel, the 
deeper, within certain limits, will these marks 
be. The blade is supposed, in Fig. 1, to have 
been held upon the stone with the plane of 
revolution of the latter at a right angle to the 
leng^i of the blade, as denoted by the line A B, 
hence the fine teeth at the edge stand also at a 
right angle to the blade. If the length of the 
blade is held at an angle to the stone, the 
marks and the teeth upon the edge will stand 
at a corresponding angle, as shown in Fig. 2, in 
which the marks represent the plane of revo- 
lution of the grindstone. Suppose, then, 
