15 grs.

In this I plunge several sheets of paper rolled into a coil (taking care
that they are covered by the solution), and exhaust the air. I leave them
thus for a few minutes, then take them out and hang them up to dry; or as
the sheets are rather difficult to pin, from the paper giving way, spread
them on a frame, across which any common kind of coarse muslin or tarletan,
such as that I inclose, is stretched.

I excite with ammonio-nitrate of silver, 30 grains to 1 ounce of water,
applied with a flat brush.

I fix in a bath of plain hypo. of the strength of one-sixth. The bath in
which the inclosed specimens were fixed has been in use for some little
time, and therefore has acquired chloride of silver.

I previously prepared my paper by _brushing_ it with the same salt
solution, and the difference of effect produced may be seen by comparing a
proof so obtained, which I inclose, with the others. This latter is of
rather a reddish-brown, and not very agreeable tint. I have inclosed the
proofs as printed on paper of Whatman, Turner, and Canson Freres, so as to
show the effect in each case. The advantages which the mode I have detailed
possesses are, I think, these:

Greater sensitiveness in the paper,

A good black tint, and

Greater freedom from spots and blemishes, all very material merits.

C. E. F.

[Our Correspondent has forwarded five specimens, four of which are
certainly very satisfactory, the fifth is the one prepared by
brushing.]

* * * * *

Replies to Minor Queries.

_The Groaning Elm-plank in Dublin_ (Vol. viii., p. 309.).--DR. RIMBAULT has
given an account of the groaning-board, one of the popular delusions of two
centuries ago: the following notice of it, extracted from my memoir of Sir
Thomas Molyneux, Bart., M.D., and published in the _Dublin University_ for
September, 1841, may interest your readers:

"In one of William Molyneux's communications he mentions the exhibition
of 'the groaning elm-plank' in Dublin, a curiosity that attracted much
attention and many learned speculations about the years 1682 and 1683.
He was, however, too much of a philosopher to be gulled with the rest
of the people who witnessed this so-called 'sensible elm-plank,' which
is said to have groaned and trembled on the application of a hot iron
to one end of it. After explaining the probable cause of the noise and
tremulousness by