_Precision in Photographic Processes._--I have for a long period observed,
and been much annoyed at the circumstance, that many of your photographic
correspondents are very remiss when they favour you with recipes for
certain processes, in not stating the specific gravity of the articles
used; also, in giving the quantities, in not stating if it is by weight or
measure.
To illustrate my meaning more fully, I will refer to Vol. viii., p. 252.,
where a correspondent, in his albumen process, adds "chloride of barium, 7-1/4
dr." Now, as this article is prepared and sold both in crystals and in a
liquid state, it would be desirable to know which of the two is meant
before his disciples run the risk of spoiling their paper and losing their
time.
How easy would it be to prefix the letter _f_ where fluid oz., dr., or
other quantity is meant.
Trusting that this hint may in future induce your correspondents to be as
explicit as possible on all points, believe me to be an