608 Dinbur Castle, its Gardens and Gardeners. 



in every ] 00. It was a supporter of both life and fire ; animals 

 could not live in air deprived of it, and flame is soon extinguished 

 when there is no oxygen to support it : also, all combustible 

 bodies burn in oxygen with increased brilliancy ; this may be 

 easily shown. So, taking a piece of charcoal attached to wire, 

 and making it redhot in the fire, he lifted the cover from one of 

 the glasses and put the burning charcoal into it ; the charcoal 

 burned with great splendour, throwing out beautiful sparks in 

 all directions. He also showed them how iron would burn in 

 oxygen gas. He took a piece of fine iron wire, coiled it up 

 in a spiral form, fastened a little cotton to one end of it, and 

 dipped it in melted sulphur ; the other end of the wire he 

 fixed to a bit of wood, in such a manner as to allow the spiral to 

 hang straight down. He lighted the sulphur, and introduced the 

 wire into the vessel containing the gas, suspending it by the wood, 

 which he placed on its mouth ; when the iron began imme- 

 diately to burn with a most brilliant light, throwing out meteor- 

 like coruscations of lighted sparks. He also showed them, in a 

 small way, the beautiful experiment of burning a little bit of 

 phosphorus in oxygen, producing a light so excessively dazzling 

 that it was almost impossible to look at it. He also showed 

 them how a candle just put out, and retaining part of the wick 

 redhot, should relight again, with a small explosion, by being 

 put in oxygen gas. He had stated already that a fifth part 

 of the bulk of the air of the atmosphere is oxygen, and he 

 should endeavour to demonstrate, in a rough way, that it 

 is so. He had borrowed the dairy-maid's lactometer, a glass 

 tube about 12 in. long and half an inch in diameter, di- 

 vided into 100 equal parts, and closed at one end. Taking 

 a bit of phosphorus, and placing it upon a small hollow cup 

 of copper, on the shelf of the pneumatic trough, a little raised 

 above the surface of the water, he inflamed the phosphorus, and 

 then placed the open end of the graduated tube, filled with atmo- 

 spheric air, over it. When the combustion ceases, the water will 

 rise in the tube, and occupy the place of the oxygen gas con- 

 sumed, and the division to which it has reached will show the 

 number of parts of oxygen in the 100 of atmospheric air. This may 

 not be the most accurate method of measuring the proportion of 

 oxygen gas in the atmosphere, for the heat of the phosphorus 

 will cause the air in the tube to expand, and part of it may 

 escape; but it affords a pretty correct idea of it. He also 

 showed them the method of transferring a gas from one vessel 

 to another, and how to mix them in particular proportions ; how 

 to catch them, confine them, and experiment with them ; how to 

 divide and measure them, with as much ease as a merchant could 

 measure a yard of cloth, or Nelly Walker measure the milk for 

 their breakfast. 





