Warmth of different Materials.—­“The indefatigable Rumford made an elaborate series of experiments on the conductivity of the substances used in clothing.  His method was this:—­A mercurial thermometer was suspended in the axis of a cylindrical glass tube ending with a globe, in such a manner that the centre of the bulb of the thermometer occupied the centre of the globe; the space between the internal surface of the globe and the bulb was filled with the substance whose conductive power was to be determined; the instrument was then heated in boiling water, and afterwards, being plunged into a freezing mixture of pounded ice and salt, the times of cooling down 136 degrees Fahr. were noted.  They are recorded in the following table:—­

Surrounded with —­                            Seconds. 
Twisted silk..................................  917
Fine lint..................................... 1032
Cotton wool.................................. 1046
Sheep’s wool.................................. 1118
Taffety....................................... 1169
Raw silk...................................... 1264
Beaver’s fur.................................. 1296
Eider down.................................... 1305
Hare’s fur.................................... 1312
Wood ashes....................................  927
Charcoal......................................  937
Lamp-black.................................... 1117

Among the substances here examined, hare’s fur offered the greatest impediment to the transmission of the heat.  The transmission of heat is powerfully influenced by the mechanical state of the body through which it passes.  The raw and twisted silk of Rumford’s table illustrate this” (Prof.  Tyndall on Heat.)

Waterproof Cloth.—­Cloth is made partly waterproof by rubbing soap-suds into it (on the wrong side), and working them well in:  and when dry, doing the same with a solution of alum; the soap is by this means decomposed, and the oily part of it distributed among the fibres of the cloth. (See “Tarpaulins.”)

Incombustible Stuffs.—­I extract the following paragraph from a newspaper.  Persons who make much use of musquito curtains, will be glad to read it. “‘The Repertoire de Chimie Pure et Appliquee’ publishes the following remarks by the celebrated chemists, mm.  D|bereiner and Oesner, on the various methods for rendering stuffs incombustible, or at least less inflammable than they naturally are.  The substances employed for this purpose are borax, alum, soluble glass, and phosphate of ammonia.  For wood and common stuffs, any one of these salts will do; but fine and light tissues, which are just those most liable to catching fire, cannot be treated in the same way.  Borax renders fine textile fabrics stiff; it causes dust, and will swell out under the smoothing-iron; so does alum, beside weakening the fibres of the stuff, so as to make it tear easily.  Soluble glass both stiffens and weakens the stuff, depriving it both of elasticity and tenacity.  Phosphate of ammonia alone has none of these inconveniences.  It may be mixed with a certain quantity of sal-ammoniac, and then introduced into the starch prepared for stiffening the linen; or else it may be dissolved in 20 parts of water, in weight, to one of phosphate, and the stuff steeped into the solution, then allowed to dry, and ironed as usual.