he metal. Still, they are extensively used, and amateurs
will find them preferable to the more expensive copper plates.

_Etching-ground._ A recipe for a cheap and yet a very good ordinary
ground has been given on p. xv. The transparent ground consists of

5 parts, by weight, of white wax.
3 " " gum-mastic.

Gum-mastic costs about thirty-five cents an ounce. Melt the wax first,
and add the gum-mastic in powder gradually, stirring all the while with
a clean glass or metal rod.

_Stopping-out varnish._ (See p. xvi.) There is a varnish sold at
painters' supply-stores under the name of "Asphaltum Varnish for
Sign-Writers' Use," which does very well. In Boston Asahel Wheeler sells
it at fifteen cents a bottle.

_Needle-holders_ are unnecessary if the points described on p. xvi are
used.

_Burnishers_ are sold at the hardware-stores, or by dealers in
watchmakers' materials. They ought not to cost above fifty cents apiece.

_Scrapers._ Same as burnishers. Price not above $1. Some dealers ask $2,
which is exorbitant.

_A lens_ can be obtained of any optician. In Boston they can also be had
of A.J. Wilkinson & Co., hardware dealers, 184 Washington St., at prices
varying from $1 to $1.50.

_India-rubber finger-gloves_ are unnecessary if you use the
"plate-lifter" described on p. xvii.

_Nitric acid._ Messrs. Powers & Weightman's "Nitric Acid, C. P." (i. e.
chemically pure), recommended on p. xvii, is 42 degrees, and Messrs. P.
& W. inform me that the strength is tolerably uniform. If you are an
enthusiastic etcher it will be best to buy a seven-pound bottle, which
is the next largest to the one-pound bottles.

_Tracing-paper_, _gelatine_, _chalk_, and _sanguine_ can be obtained at
the artists' material stores.

_Emery-paper._ Hardware-stores. Price four cents a sheet.

_Roller for revarnishing._ See Note 5.

To the tools and materials mentioned by M. Lalanne the following must be
added: _Whiting_, _benzine_, _turpentine_, _alcohol_, _willow charcoal_.
The last-named article can be supplied by Mr. Geo. B. Sharp, of 45 Gold
St., New York, before mentioned.

[4] (p. 11.) I wrote to M. Lalanne to find out the ingredients of the
_petit vernis liquide_ and _vernis au pinceau_, but he says that he does
not know, and that the recipes are a secret of the maker of these
varnishes. The asphaltum varnish mentioned on p. xvi and in Note 3 does
excellently well, however, both for stopping out and retouch