TABLE

Of the Heating Power of various Combustible Substances, exhibiting the utmost Quantity of Water evaporated by the Given Weights, and the smallest Quantity of Air capable of producing Total Combustion.

To ESTIMATE DISTANCE-Observe how many seconds elapse between a flash of lightning and the thunder, and multiply them by 1142, the number of feet sound travels in a second, the product will be the distance in feet. The same process may be applied to the flash and report of a gun, or any other sound, provided we can ascertain the time at which it is produced, and the interval that elapses before it reaches the ear..

Illustration. Saw a flash of lightning five seconds before I heard the thunder: required the distance.

In the absence of a watch, the pulsations at the wrist may be counted as seconds, by deducting one from every seven or eight..

PRISMATIC DIAMOND CRYSTALS FOR WINDOWS.-A hot solution of sulphate of magnesia, and a clear solution of gun arabic, mixed together. Lay it on hot. For a margin or for figures, wipe off the part you wish to remain clear with a wet towel.

PERFECTLY BLACK HARD GLASS-Plain paste, 600 parts; zaffre, 3 parts; manganese, 3 parts; iron, & parts.

TABLE

Of the Revolutions per Mile of Driving Wheels, and Consumption of Steam and Water for each sized Wheel; taking the steam admitted to each cylinder as exactly one cube foot, ut a gross pressure of 98lbs. or 83lbs. on the spring balance.

Note. As there are two cylinders at work in a locomotive, consequently there are four cylinders of steam for each revolution.

MODELLING WAX.-This is made of white wax, which is melted and mixed with lard to make it malleable. In working it, the tools and the board or stone are moistened with water, to prevent its adhering; it may be colored to any desirable tint with dry

color.