tail, the land would then, as now, revert
on failure of issue, unless the entail had been previously barred. The
right of alienation was gradually acquired; the above statute of _Quia
Emptores_ was the most important enactment in that behalf. With this
exception, and the right to devise and to bar entails, the lords of manors
have the same interest in the land held by freeholders of the manor that
they had in times of subinfeudation. (Blackstone's _Comm._, vol. ii. ch.
287., may be carefully consulted.)

H. P.

Lincoln's Inn.

* * * * *

PHOTOGRAPHIC CORRESPONDENCE.

_Spots on Collodion Pictures, &c._--The principal difficulty I experience
in the collodion process is occasioned by the appearance of numberless very
minute spots or points over the whole extent of the picture. These
occurring on the whites of my pictures (positives) give them a rough,
rubbed, appearance and want of _density_, which I should feel obliged if
any of your correspondents can teach me how to overcome.

One of your photographic querists inquires the remedy for his calotype
negatives darkening all over before the minor details are brought out. I
had for a long time been troubled in the same way, but by diminishing the
aperture of my three-inch lens to half an inch, and reducing the strength
of my sensitising solution to that given by DR. DIAMOND, and, in addition,
by developing with gallic acid alone until the picture became tolerably
distinct in all its parts, and then applying the gallo-nitrate, I have
quite succeeded in obtaining first-rate negatives. It is well to prepare
only a small quantity of aceto-nitrate at once, as the acetic acid is of a
sufficiently volatile nature to escape from the solution, which is a not
unfrequent cause of the general darkening of the picture. It would be well
to substitute a more fixed acid for the acetic if this be practicable, as
it is in the collodion process, where tartaric is recommended.

H. C. COWLEY.

Devizes, Wilts.

_The Double Iodide Solution._--The great difference in the quantity of
iodide of potassium ordered by different persons, to dissolve a given
weight of iodide of silver in a given volume of water, has induced me to
make some experiments on the subject. I find that using pure nitrate of
silver, and perfectly pure iodide of potassium (part of a parcel for which
Mr. Arnold, who manufactures iodine on a large scale in this island, got a
medal at the E