The only thing to be done, where feed connections are made in the manner
described, is to change them, and by changing them at once much trouble,
or even a disastrous explosion, may be avoided. Put the feedpipe in
through the front head, at the point marked _p_ in Fig. 1, drill and tap
a hole the proper size for the feed pipe, cut a long thread on the end of
the pipe, and screw the pipe through the head, letting it project through
on the inside far enough to put on a coupling, then screw into the
coupling a piece of pipe not less than eight or ten feet long, letting it
run horizontally toward the back end of the boiler, the whole arrangement
being only from 3 to 4 inches below the water line of the boiler, and hot
or cold water may be fed indifferently, without fear of danger from
ruptured plates or leaky seams. In short, put in a "top feed," and avoid
further trouble.--_The Locomotive_.

* * * * *

[MICROSCOPICAL JOURNAL.]

IRON PRINTING AND MICROSCOPIC PHOTOGRAPHY.

By C.M. VORCE, F.R.M.S.

I. FORMULAS FOR PRINTING SOLUTIONS.

_Blue Prints_.--The best formula for this process, of many that I have
tried, is that furnished by Prof. C.H. Kain, of Camden, N.J., in which
the quantity of ammonio-citrate of iron is exactly double that of the red
prussiate of potash, and the solutions strong. This gives strong prints
of a bright dark blue, and prints very quickly in clear sunlight.

Dissolve six grains of red prussiate of potash in one drm. of distilled
water; in another drm. of distilled water dissolve twelve grains of
ammonio-citrate of iron. Mix the two solutions in a cup or saucer, and at
once brush over the surface of clean strong paper. Cover the surface
thoroughly, but apply no more than the paper will take up at once; it
should become limp and moist, but not wet. The above quantity of
solution, two drms., will suffice to sensitize ten square feet of paper,
or three sheets of the "regular" size of plain paper, 18x22. As fast as
the sheets are washed over with the solution, hang them up to dry by one
corner. The surplus fluid will collect in a drop at the lower corner, and
can be blotted off.

_Black Prints_.--Wash the paper with a saturated solution of bichromate
of potash, made quite acid with acetic acid. After printing, wash the
prints in running water for twenty to thirty minutes, then float them
face down on a weak solution (five to ten per cent.) of protosulphate