388 THE WORLD OF LIFE 



highest powers of the artist and craftsman in the making of 

 ornaments, coins, drinking-vessels, etc., many of which have 

 come down to ns from early times, sometimes showing a beauty 

 of design which has never been surpassed. Our own earliest 

 rudiments of civilisation were probably acquired from the 

 Phoenicians, who regularly came to Cornwall and our southern 

 coasts to purchase tin. 



Each of the seven metals (and a few others now in com- 

 mon use) has very special qualities which renders it useful for 

 certain purposes, and these have so entered into our daily life 

 that it is difficult to conceive how we should do without them. 

 Without iron and copper an effective steam-engine could not 

 have been constructed, our whole vast system of machinery 

 could never have come into existence, and a totallv distinct 

 form of civilisation would have developed — perhaps more on 

 the lines of that of China and Japan. Is it, we may ask, a 

 pure accident that these metals, with their special physical 

 qualities which render them so useful to us, should have ex- 

 isted on the earth for so many millions of years for no appar- 

 ent or possible use ; but becoming so supremely useful when 

 Man appeared and began to rise tow^ards civilisation ? 



But an even more striking case is that of the substances 

 which in certain combinations produce glass. Sir Henry Ros- 

 coe states that silicates of the alkali metals, sodium and potas- 

 sium, are soluble in water and are non-crystalline ; those of 

 the alkaline earths, calcium, etc., are soluble in acid and are 

 crystalline; but by combining these silicates of sodium and 

 calcium, or of potassium and calcium, the result is a substance 

 which is noi soluble either in water or acids, and which, when 

 fused forms glass, a perfectly transparent solid, not crystallised 

 but easily cut and ]3olished, elastic within limits, and when 

 softened by heat capable of being moulded or twisted into an 

 endless variety of forms. It can also be coloured in an infinite 

 variety of tints, while hardly diminishing its transparency. 



The value of cheap glass for windows in cold or changeable 

 climates cannot be over-estimated. Without its use in bottles, 



