78 THE EEASOK WHY. 



' Whereupon are the foundations thereof fastened ? or who laid the con 

 stone thereof." JOB xxxviir. 



804. Why does lolled water taste fiat and insipid ? 

 Because the carbonic acid has been driven off by boiling 1 . 



805. Why does leer which has been standing in a glass 

 taste flat ? 



Because its carbonic acid has escaped as carbonic acid gas. 



806. Why, when we look into a glass of champagne, do ice 

 see bubbles spontaneously appear at the bottom, and then 

 rise to the top ? 



Because, in the places where the bubbles are formed, the liquid 

 carbonic acid is evolving into carbonic acid gas. 



807. Why do the bubbles arise from two or three points in 

 columns, rapidly succeeding each other ? 



Because, when the formation of gas once begins, and bubbles 

 ascend, there is less pressure in the line of the column if bubbles ; 

 the carbonic acid, therefore, draws towards those points as the 

 easiest channel of escape. 



These explanations equally apply to the " working" of beer, by which yeast is 

 produced ; to the effervesence of various waters, acidulated drinks, ginger beer, 

 ic., and also to the " sponging" of bread, 4c. 



808. Why does gunpowder explode ? 



Gunpowder is made of a very intimate mechanical mixture of 

 nitrate of potash, charcoal, and sulphur. When these substances 

 are heated to a certain degree, the nitrate of potash is decomposed, 

 and its oxygen combines with the charcoal and sulphur, instan- 

 taneously forming large volumes of carbonic acid gas and nitrogen, 

 which, seeking an escape, produce an explosion. 



809. Why does charcoal act as a powerful disinfectant ? 

 Because the carbon readily absorbs, and combines with various 



gases, neutralising their offensive odours, and destroying their 

 unhealthy properties. 



Let us now pause f* a few moments to consider the importance of those two 

 great divisions of nature, Air and Water, and to reflect upon the wisdom of some 

 of those laws which are connected with the phenomena thereof, and which have 

 not yet been sufficiently explained. 



We have seen that the air is a thin elastic boc^i surrounding the globu ; thi 



