692 SCIENCE PROGRESS 



But when acids are mentioned, always think of sour-stuff — 

 oxygen is par excellence the acid-giving element ; the text-books 

 may tell you of hydrogen as characteristic of acids and even 

 mislead you into a temporary belief in non-existent nonsensities 

 called hydrogen ions : trust them not but pin your faith to 

 oxygen; learn to think of oxygen as the most wonderful element 

 known to us and water as containing it in perhaps its most 

 active form ; at the same time, bear in mind that it has not only 

 an acid aspect but is also the progenitor of earths. Iron, you 

 know, is converted only too easily into the earthy substance 

 iron-rust by combination with atmospheric oxygen under the 

 conjoint influence of liquid water and carbonic acid — hence the 

 need of protecting it by paint or of keeping it in a dry, warm 

 place. At the smithy forge, iron and oxygen burn together into 

 a brittle black scale — again an earthy substance. Those who 

 have played with magnesium know that it not only burns 

 brilliantly but that it is converted into a white earth. Zinc 

 is systematically burnt to form zinc oxide, which is largely used 

 as the basis of white paint. Both magnesium and zinc oxide 

 look like lime and the former tastes like lime : whence Brer 

 Rabbit— who argued, you will remember, that what looked like 

 Sparrer Grass and tasted like Sparrer Grass was Sparrer Grass 

 — would say they are limes or earths ; and vice versa that an 

 earth like lime must belong to the oxides. This kind of argu- 

 ment has in fact led chemists — led Humphrey Davy — to discover 

 that lime is the oxide of a metal much like magnesium. 



Just think what is got out of limestone by considered argu- 

 ment and measured study ! Itself a neutral substance and a 

 typical salt, it is resolved into two typical oxides — an acidic 

 oxide and an earthy, alkylic oxide. In deciphering its story, 

 you may learn almost all that is necessary for an agriculturist 

 to learn of chemical method. I say this because I feel that it in 

 no way receives the attention it deserves — because it is one of 

 the substances which should always live in your thoughts. 



Ordinarily, it is neglected, scarce seen ; the attempt is rarely 

 made really to decipher its unobtrusive mysteries : 



The world is too much with us ; late and soon, 



Getting and spending, we lay waste our powers : 

 Little we see in Nature that is ours ; 



... for everything we are out of tune ; 

 It moves us not. 



