-As the length of the stick's shadow is to the length of the stick
itself, so is the length of the shadow of the object to the object's
height.

_By Reflection_

Place a vessel of water upon the ground and recede from it until you see
the top of the object reflected from the surface of the water. Then it
will be:--As your horizontal distance from the point of reflection is
to the height of your eye above the reflecting surface, so is the
horizontal distance of the foot of the object from the vessel to its
altitude above the said surface.

_Instrumentally_

Read the vertical angle, and multiply its natural tangent by the
distance between instrument and foot of object; the result is the
height.

When much accuracy is not required vertical angles can be measured by
means of a quadrant of simple construction. The arc AB is a quadrant,
graduated in degrees from B to A; C, the point from which the plummet P
is suspended, being the centre of the quadrant.

_When_ the sights AC are directed towards any object, S, the degrees
in the arc, BP, are the measure of the angle of elevation, SAD, of the
object.

TO FIND THE DEPTH OF A SHAFT

_Rule_:--Square the number of seconds a stone takes to reach the bottom
and multiply by 16.

Thus, if a stone takes 5 seconds to fall to the bottom of a shaft--

5 squared = 25; and 25 X 16 = 400 feet, the required depth of shaft.

DESCRIPTION OF PLAN FOR RE-USING WATER

Where water is scarce it may be necessary to use it repeatedly. In a
case of this kind in Egypt, the Arab miners have adopted an ingenious
method which may be adapted to almost any set of conditions. At a is a
sump or water-pit; b is an inclined plane on which the mineral is washed
and whence the water escapes into a tank c; d is a conduit for taking
the water back to a; e is a conduit or lever pump for raising the
water. A certain amount of filtration could easily be managed during the
passage from c to a.

COOLING COMPOUND FOR HEATED BEARINGS

Mercurial ointment mixed with black cylinder oil and applied every
quarter of an hour, or as often as expedient. The following is also
recommended as a good cooling compound for heavy bearings:--Tallow 2
lb., plumbage 6 oz., sugar of lead 4 oz. Melt the tallow with gentle
heat and add the other ingredients, stirring until cold.

CLEANING GREASY PLUMMER BLOCKS

When, through carelessness or unpreventable cause, plummer blocks
and other detachable portions of machinery be