Irregularity of the Type, the rough dawbing of the Printing-Ink thereon, and the Vari-
ation made by the different Lights and Shadows. Nor is a Point made with a Pen, or
by a Copper-Plate, at all less ill-shapen and ugly ; nor can the sinest Writing in the World
stand the Test of this Instrument, but will appear before it like the bungling Scrawls
of a School-Boy, made with Charcoal on a whited Wall.
PLATE I. FIG. 3.
The Edge of a Razor
THIS Figure represents the Edge (about half a Quarter of an Inch long) of a very
sharp Razor well set upon a good Hone,
and so placed between the Object-Glass and
the Light, that there appeared a Reflection from the very Edge, which is shewn by the
white Line
a, b, c, d, e, f.
When we speak of any thing as extremely keen, we usually compare it to the Edge
of a Razor ; but we find, when examined thus, how far from Sharpness even a Razor's
Edge appears : That it seems a rough Surface, of an unequal Breadth from side to side,
but scarce any where narrower than the Back of a pretty thick Knife : That it is neither
smooth, even, nor regular ; for it is somewhat sharper than elsewhere at d, indented about
b, broader and thicker about c, unequal and rugged about e, and most even between a, b,
and e, f, though very far in any Place from being really straight.
The Side immediately below the Edge, and what the naked Eye accounts a Part of it,
g, b, y, k, had nothing of that Polish one would imagine Bodies so smooth as a Hone and
Oil should give it ; but was full of innumerable Scratches crossing one another, with Lines
here and there, more rugged and deep than the rest, such as g, b, y, k, o, occasioned pro-
bably by some small Dust falling on the Hone, or some more flinty Part of the Hone
itself.
The other Part of the Razor L L, which had been polished on a Grind-stone, appeared
like a plowed Field, full of Ridges and Furrows.
The irregular dark Spot m, n, seemed to be a little Speck of Rust ; corrosive Juices ge-
nerally working in such a manner.
This Examination proves, how rough and unseemly (had we microscopic Eyes) those
Things would appear, which now the Dulness of our Sight makes us think extremely
neat and curious : And, indeed, it seems impossible by Art to give a perfect Smoothness
to any hard and brittle Body ; for Putty, or any other soft Powder, employed to polish
such Body, must necessarily consist of little hard rough Particles, each whereos cut-
ting its Way, must consequently leave some kind of Furrow behind it. In short, this Edge
of a Razor, had it been really as the Microscope shews it, would scarce have served to chop
Wood, instead of shaving a Man's Beard.
N. B. The black Part of this Figure is only designed to make the rest more visible.
The Scale is intended to measure the Figure by.
