nd cheapest form of apparatus to heat such compounds
for examination? A. Mix the substance with a little pure hydrochloric
acid and glycerin, and introduce into the flame on a coil of platinum
wire.

1. Has soup prepared by dissolving meat bones in a Papin's digester
ever been known to produce ossification of any of the soft tissues? A.
We have never heard of such a result. 2. Has it ever been known to
produce a new crop of teeth in toothless persons? A. We have no data
as to such a fact.

I have seen a statement that May 19, 1780, was so dark a day that
candles were necessary everywhere; and I have heard that another
occurred about the year 1820. Has any scientific explanation ever been
given of this phenomenon? A. The darkness on the days you mention were
the result of solar eclipses. They occurred on days of unusual
cloudiness. Perhaps the darkest day in modern history was that caused
by the total solar eclipse in the year 1806.

(12) A.B. says: 1. I have built a boat 15 feet long and 4 feet 6
inches wide. How large a boiler and engine do I require to work her to
best advantage? She is 22 inches deep from top of rail to top of keel.
A. Cylinder, 21/2 x 3 inches; boiler, 20 inches in diameter and 3 feet
high. Propeller, 18 to 20 inches in diameter, and of 3 feet pitch. 2.
How fast ought she to run? A. Probable speed, 5 miles an hour in
smooth water.

(13) L.L. asks: 1. Does it make any difference in what position a
watch is in when running? A. For watches adjusted to temperature and
position, it does not make much difference. 2. When not being carried,
what position should it be left in? A. In the case of ordinary
watches, we imagine that the wear will be rather more uniform when
they are in a vertical position. 3. If a person sleeps in a cola room,
would a watch be better under his pillow than on a table or hung up in
the same room? A. It is best not to subject them to great changes of
temperature.

(14) W.G. says, in reply to C.W.W., who has an engine, of 2-5/8 inches
bore and 4 inches stroke, which runs slower with increase of pressure:
Having had much experience with small engines and boilers, I will
state that I have had the same difficulty when using an upright
tubular boiler, and discovered the following to be the cause: The
upper portions of the tube superheat the steam to such a degree as to
prevent lubrication on the valve and piston surface by condensation,
and thereby reduce the speed of engine. Eve