black and white. The proportions I use are 8 ounces to the pint of
water. Almost the only other complaints I now hear are traceable to
over-exposure or lack of intelligent cleanliness in the handling of the
paper. The operator, after having been dabbling for some time in hypo,
or pyro, or silver solution, gives his hands a wipe on the focusing
cloth, and straightway sets about making an enlargement, ending up by
blessing the manufacturer who sent him paper full of black stains and
smears. Argentic paper is capable of yielding excellent enlargements,
but it must be intelligently exposed, intelligently developed, and
cleanly and carefully handled.

* * * * *




THE MANUFACTURE AND CHARACTERISTICS OF PHOTOGRAPHIC LENSES.


At a recent meeting of the London and Provincial Photographic
Association Mr. J. Traill Taylor, formerly of New York, commenced his
lecture by referring to the functions of lenses, and by describing the
method by which the necessary curves were computed in order to obtain a
definite focal length. The varieties of optical glass were next
discussed, and specimens (both in the rough and partly shaped state)
were handed round for examination. The defects frequently met with in
glass, such as striæ and tears, were then treated upon; specimens of
lenses defective from this cause were submitted to inspection, and the
mode of searching for such flaws described. Tools for grinding and
polishing lenses of various curvatures were exhibited, together with a