50 SCIENTIFIC AMUSEMENTS. 



of certain saline substances to interfere with the free burning of 

 easily combustible bodies treated therewith is often utilised for 

 the purpose of making such substances more or less fireproof. 

 Prepare some ordinary laundress's starch paste by rubbing up solid 

 starch to a cream with a little water in a basin with a spoon, and 

 then pouring boiling water into the basin, well stirring the while. 

 Muslins, &c., starched with this will flame readily if fired when 

 quite dry; but if a little alum, or, better still, the salt termed 

 tung state of sodium, be mixed with the starch paste, it will be 

 found that muslins starched with the mixture will no longer take 

 fire and blaze up when a light is put to them ; if held in a candle 

 flame they will char where the flame touches them, but the burning 

 portion will not spread around. The most effective way of show- 

 ing this is to make two small wire-frames, shaped like the wicker 

 dress-stands used by ladies, so that when draped, one with pre- 

 pared muslin and one with ordinary starched material, they may 

 represent two miniature ball dresses, something like dressed dolls. 

 On putting a light to the first nothing remarkable happens, but 

 on doing the same to the second the muslin takes fire and flames 

 up, and in a few seconds only the bare wire-stand is left. Of 

 course this experiment must not be tried in a room where there 

 are curtains or other furniture that might be easily set on fire 

 should burning fragments of muslin fly about in the air. 



Vaporisation of Liquids without Ebullition or Boiling. 



In order to convert a liquid into vapour it is not necessary to 

 boil it from beneath. By holding a hot plate of iron over water 

 in a shallow saucer the water is quickly evaporated and dried up 

 without visible ebullition ; in the same kind of way many other 

 fluids will gradually form vapour and disappear by simple exposure 

 to air at the ordinary temperature. When the pavement dries 

 after a shower, or wet clothes after washing, the water gradually 

 assumes the condition of vapour which becomes intermingled with 

 the air, and is removed by winds and currents. In colder regions 

 of the air the vapour thus present in consequence of evaporation 

 from the sea and land becomes more or less condensed just as the 

 steam from a tea-kettle ; mist or cloud thus first results, consisting 

 of minute drops or vesicles of liquid water floating about in the 

 air. When these run together or coalesce so as to form larger 

 drops which are heavy enough to fall quickly, rain results; if 

 the drops fall through a very cold stratum of air so as to freeze 

 before they reach the earth, hail is produced ; whilst if the mist 

 is chilled to the freezing point under certain conditions the 



