216 SCIENTIFIC AMUSEMENTS. 



matter, chiefly carbonate of lime like eggs ; whilst the bones of 

 animals (such as oxen, sheep, and mankind) are in the main built 

 up in the same sort of way, but with a different sort of calcareous 

 matter as stiffening agent, chiefly phosphate of lime. Both phos- 

 phate and carbonate of lime, however, are dissolved out by diluted 

 hydrochloric acid ; so that if the shoulder blade of a sheep, the rib 

 of an ox, the claw of a crab, or any such animal part, be immersed 

 for some days in water to which some hydrochloric acid has been 

 added, the mineral matters are dissolved out, and a flexible gristly 

 soft animal tissue is left ; in this way a long thin rib or leg bone 

 may be softened and a knot tied on it. 



On the other hand, if a bone be strongly heated in a vessel from 

 which the air is excluded, the animal matter is destroyed, and the 

 mineral matter left as a brittle porous mass retaining the shape of 

 the bone, and black with charcoal deposited throughout its sub- 

 stance by the decomposition of the animal matter (Expt. 202); 

 whilst if the blackened bone be heated again in contact with air, or 

 if air be admitted freely during the first heating, the carbonaceous 

 matter is burnt entirely away, and a nearly white porous fragile 

 mass results, consisting solely of the mineral matter originally 

 present in the bone. 



Expt. 254. To set fire to Tinfoil. Spread out on a plate a 

 piece of thick tinfoil, place on it a teaspoonful of solid nitrate of 

 copper reduced to powder in a mortar, sprinkle a little water on 

 the powder, and quickly wrap up the whole in the tinfoil. The 

 moist copper nitrate will act rapidly on the tinfoil producing a 

 large amount of heat, sometimes sufficient to cause the tinfoil to 

 take fire visibly ; the action in this case is not unlike that taking 

 place in Expt. 251, but is of a more complicated character. 



Expt. 255. To melt a Threepenny piece in a Walnut shell 

 During the deflagration of combustible bodies in contact with 

 substances containing a good deal of oxygen like saltpetre, a very 

 intense heat is often produced whilst the action lasts. Mix 

 together two parts of finely powdered loaf sugar and one of 

 potassium chlorate, both substances being powdered separately 

 (Expt. 260, Caution), and mixed by pouring from one paper to 

 another and back again several times. Fill a walnut shell with 

 the mixture and place in the centre a threepenny piece, and then 

 set fire to the whole with a spill ; a vigorous flare-up will result, 

 and so much heat will be produced during the action that the coin 

 will usually be melted down. 



Expt. 256. To set fire to a Solid by touching with a Liquid. 

 The mixture of potassium chlorate and sugar used in the last 

 experiment possesses the curious property of bursting into flame 



