re from the
originals in public libraries and private collections."

This important collection may possibly be unknown to some of your readers
who take an interest in matters liturgical.

W. SPARROW SIMPSON.

Having made it a point, for some years past, to preserve at least one copy
of each Occasional Form of Prayer, and wishing to comply with MR.
LATHBURY'S request, I send a list of those in my own possession.

Form and Thanksgiving for Delivery of the Queen, and Birth of a Prince.
1841.

Form and Thanksgiving for Preservation of the Queen "from the atrocious
and treasonable Attempt against her sacred Person." 1842.

Form and Thanksgiving for abundant Harvest. 1842.

Form and Thanksgiving for Delivery of the Queen, and Birth of a
Princess. 1843.

Form and Thanksgiving for Delivery of the Queen, and Birth of Prince.
1844.

Form and Thanksgiving for Victories in the Sutledge. 1846.

Form and Thanksgiving, for Delivery of the Queen, and Birth of a
Princess. 1846.

Form for Relief from Dearth and Scarcity. 1846.

Form for Removal of Dearth and Scarcity. Fast. 1847.

Form and Thanksgiving for abundant Harvest. 1847.

Form and Thanksgiving for Delivery of the Queen, and Birth of a
Princess. 1848.

Form for Maintenance of Peace and Tranquillity. 1848.

Form for Removal of Disease. 1849.

Form and Thanksgiving for Removal of Disease. 1849.

Form and Thanksgiving for Delivery of the Queen, and Birth of a Prince.
1850.

ABHBA.

* * * * *

PHOTOGRAPHIC CORRESPONDENCE.

_Photographic Query._--Given the diameter and focal length of a simple
achromatic lens; at what distance from it must a diaphragm of given
diameter be placed to give the best possible image?

O.

_Improvement in Collodion._--As there are many photographers who are not
members of the Photographic Society, and who do not see the journal
published by that body, a statement of what I think will be found a very
material improvement in the manufacture of collodion may not be
unacceptable to the readers of "N. & Q." To five drachms of pure _washed_
ether, add one drachm alcohol 60deg over proof, and dissolve therein
sufficient soluble cotton to make it of the consistence of oil (the exact
quantity must depend rather upon the dexterity of the operator, as the
thicker it is the more difficult to use) then add twenty m