of sheet copper about 6 inches in diameter _(b)_ and rests on
a tripod stand about 14 inches high _(c)_, which is covered with coarse
wire gauze _(e)_, and is surrounded with a screen of thin sheet copper
_(d)_. Within the latter is placed an argand burner _(f)_ with glass
chimney. The cover _(b)_ has four holes arranged, as seen in Fig. II., No.
4 to contain a Page's[A] or Scheibler's regulator, No. 3 the thermometer,
Nos. 1 and 2 the test tubes containing the explosive to be tested. Around
the holes 1 and 2 on the under side of the cover are soldered three pieces
of brass wire with points slightly converging (Fig. III.); these act as
springs, and allow the test tubes to be easily placed in position and
removed.

[Footnote A: See _Chem. Soc. Jour._, 1876, i. 24. F.J.M. Page.]

~Test Tubes~, from 5-1/4 to 5-1/2 inches long, and of such a diameter that
they will hold from 20 to 22 cubic centimetres of water when filled to a
height of 5 inches; rather thick glass is preferable. Indiarubber
stoppers, fitting the test tubes, and carrying an arrangement for holding
the test papers, viz., a narrow glass tube passing through the centre of
the stopper, and terminating in a platinum wire hook. A glass rod drawn
out and the end turned up to form a hook is better.

~The Thermometer~ should have a range from 30 deg. to 212 deg. F., or from 1 deg. to
100 deg. C. A minute clock is useful.

~Test Paper.~--The test paper is prepared as follows:--45 grains (2.9
grms.) of white maize starch (corn flour), previously washed with cold
water, are added to 8-1/2 oz. of water. The mixture is stirred, heated to
boiling, and kept gently boiling for ten minutes; 15 grains (1 grm.) of
pure potassium iodide (previously recrystallised from alcohol, absolutely
necessary) are dissolved in 8-1/2 oz. of distilled water. The two
solutions are thoroughly mixed and allowed to get cold. Strips or sheets
of white English filter paper, previously washed with water and re-dried,
are dipped into the solution thus prepared, and allowed to remain in it
for not less than ten seconds; they are then allowed to drain and dry in a
place free from laboratory fumes and dust. The upper and lower margins of
the strips or sheets are cut off, and the paper is preserved in well-
stoppered or corked bottles, and in the dark. The dimensions of the pieces
of test paper used are about 4/10 inch by 8/10 inch (10 mm. by 20 mm.).[A]

[Footnote A: When the paper is freshly prepar