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 become clogged with sticky deposits of grease and impurities, a simple mode of cleansing the same is to take about 1000 parts by weight of boiling water, to which add about 10 or 15 parts of ordinary washing soda. Keep the water on the boil and place therein the portions of the machine that are to be cleaned; this treatment has the effect of quickly loosening all grease, oil, and dirt, after which the metal is thoroughly washed and dried. The action of the lye is to form with the grease a soap soluble in water. To prevent lubricating oil hardening upon the parts of the machinery when in use, add a third part of kerosene. AN EXCELLENT ANTI-FRICTION COMPOUND