in the printing-frame, holding it in its place with a couple of tacks,
film-side next the lens, just as in printing; then stand the printing
frame on its edge on the flat board, and place the ground glass in front
of it--when I say in front of it, I mean not between the negative and
lens, but between the light and the negative. The ground glass can
conveniently be placed in another printing frame, and both placed up
against each other. I then bring my camera into play, and so adjust the
draw and distance from the negative, till I get the picture within the
disk on my ground glass. I find the best way is to gum a transparency
mask on the inside of the ground glass; this permits of the picture being
more easily brought within the required register. This done, focus
sharply, cap the lens, and then proceed to make the exposure.

Now, what shall I say regarding exposure? Just let us bear in mind again
that it is merely a printing process we are following up, as you will all
know that in printing no two negatives are alike in the time they
require. So in this case no two negatives are the same in their required
exposure. Still, with the plates I am going to use, so wide is their
range for exposure that but few failures will be made on this score,
provided we are on the safe side, and expose fully.

Although these plates are not nearly so fast as gelatine plates, it may
surprise you to be told that working with a negative which to daylight at
this dull time of the year required an exposure of sixteen minutes, will,
I hope, give me good results in about a tenth of this time; and this I
obtain by burning magnesium ribbon.

At first the error I fell into when using magnesium ribbon was too much
concentration of light. I now never allow the ribbon, when burning, to
remain in one position, but keep it moving from side to side, and up and