90 The Ottawa Naturalist. |J u 'y 



Heat slowly and carefully a little of the wood, cut into 

 small pieces, in the bottom of a closed test-tube. Clear drops 

 of a tasteless liquid like water form on the inside of the tube above 

 the wood ; and as the water gathers, the charcoal appears. The 

 water evidently comes out cf the dry wood and leaves the 

 charcoal behind. 



It can easily be shown, by means of a hand balance, that a 

 piece of charcoal (from a stove) weighs less than a piece of the 

 dry wood, equal in size, from which the charcoal was obtain- 

 ed". 



It is plain then that dry white wood contains both charcoal 

 and water, and that when the water is driven out by the heat, 

 the charcoal can be seen. And so it appears that the water in 

 the wood hides the charcoal, else the wood would lock black, and 

 the charcoal conceals the water, else the wood would feel wet. 



It may now be stated that when two substances as charcoal 

 and water in this case are so united together that they conceal 

 each other's properties, the two substances are said to be chemi 

 cally united or combined ; and the substance they fcrm by their 

 union is called a chemical compound. Thus dry wood may be 

 regarded as a chemical compound of carbon and water. 



Next mix together, in a bottle, water and powdered char- 

 coal. Do they unite chemically? They do not conceal each 

 other's properties. The black charcoal can still be seen and the 

 water felt. They now form, not a chemical compound, but a 

 chemical or physical mixture. But how can the charcoal and 

 water be got to unite chemically? They must have been chemi- 

 cally separate before they united to form wood; but ive don't 

 know, at present, how to ccmpel them to combine to form wood. 



Put finely divided wood, to the depth of about an inch, into 

 a test-tube loosely closed with a cork or the thumb, -and apply 

 heat until the tube is filled with smoky gas ; then without 

 withdrawing the heat remove the cork cr thumb, and try with a 

 match until you succeed, to set fire to the gas in the tube. How 

 do you account for this combustible "wood-gas"? Since this 

 gas will burn, it cannot be water-gas (steam) ; so we must con- 

 clude, since chemists find that pure wood is composed entirely 

 of carbon and water, that this gas was formed in some way from 

 these two substances in the wood. It should be noted here that 

 the water set free by the heat soon becomes colored by some 

 ether liquid, and that a mass of charcoal remains in the tube after 

 the water and the combustible gas has been all expelled. It will 



