Popular Science Monthly
IT is not difficult to undcrsland iiow combustion may take placi' without any apparent cause. Consider some of the everyday examples of combustion. Coal requires a considerable amount of coaxing before it will ignite, hence the necessity to lay a fire with wood to start the coal and paper to light the wood. A poker at a bright red heat will ignite a gas jet ; upon cooling to a dull red heat it will set fire to paper; and after still further cooling will explode gun- powder.
Phosphorus takes fire at a little above ioo° F., by no means a high tempera- ture. But the vapour of liquid phos- phuretled hydrogen is even more easily inflamed, requiring for its ignition a temperature less than the ordinary temperature of a room. Hence, when- ever this substance comes into contact with the air it takes fire at once. This is an example of so-called spontaneous combustion, and only differs from the combustion of a candle in the circum- stance that no outside source of heat is required to start the reaction.
Phosphuretted hydrogen can be made by placing small fragments of yellow phosphorus in a flask together with some quicklime and covering with water. Upon boiling the water phosphuretted hydrogen is formed and escapes from a bent glass tube passing through the cork, the other end of the tube dipping below the surface of warm water con- tained in a dish. As each bubble of gas comes into contact with the air it takes fire and forms white powdery phos- phorous pento.xide. — H. T. Gr.\v.
����This Loop Arrange- ment Shifts theCon- trol Back Into the Hand
��The Phosphorus Powder Produces a Series of Smoke Rings which Expand as They Rise
��Fitting Penholders to Crippled Hands
AMOXC. the many appliances which L have been devised to lessen the care of soldiers injured in the war are various kinds of penholders for those with crippled hands. If the thumb and fore- finger or the forefinger and middle finger are stiff, or even if all three fingers are not capable of bending, a holder in the form of a loop may be successfully used. This arrangement, in which the control is shifted back into the hand, is shown in Fig. i.
If the thumb, ring finger and little finger have been amputated, a holder like the one shown in Fig. 2 is of service. The enlarged por- tion enables the index and middle fingers to grip it securely and also keeps the holder from turning.
When the thumb is good, but all four fingers injured so that only their stubs are left, a trian- gular block is made that fits the palm of the hand on one side, and has a groove for the thumb on the other side. A firm grasp can be obtained by pres- sure with the thumb. This de- vice is shown very clearly in Fig. 3.
Casualties are so varied that no stand- ard device can be established. Some are injured in such a way that their hand trembles when writing. A thick holder of wood or cork, which only requires holding but no bending with the fingers, is very successful in this case.
���For Use Wheri
Thumb and Two
Last Fingers Have
���When the Hand of the Injured Trem- bles While Writing