244 Natural Theology. 



They may weave their iron tracks like a net-work 

 over the continents, span the rivers with iron 

 arches, plough the ocean with iron hulls, stretch 

 iron wires from city to city, cover the roads with iron 

 cars, and build iron palaces, and yet the mountains 

 of iron ore will hardly be diminished in size. 



It might seem at first thought, that want of design 

 is shown in the fact, that so useful a substance is 

 seldom if ever found in a pure state. But a mine 

 of solid iron would hardly pay for workii g. So 

 hard a substance is it in a pure state, that huge 

 masses would seem to defy the miner's power. But 

 as a brittle ore, it is easily quarried, and is thus 

 brought readily into the conditions most serviceable 

 to man. 



Its first property worthy of special notice is its 

 chemical relation to oxygen and carbon, by which 

 its ores so readily yield in the blast furnace their 

 oxygen, unite with carbon, and become cast-iron, 

 with the physical property of expanding just as it 

 solidifies, so as to fill the mould and give the sharp- 

 est outline to the finest figures on the pattern. 



If we consider it as cast-iron alone, we find it 

 perfectly adapted to its purpose. As wrought-iron, 

 it is obedient to the fire and hammer, taking the 

 thousand forms which the workman demands, bend- 

 ing, yielding, and welding, and then, when cold 

 again, holding the form he has given it with the 

 power of a giant. 



Combined with carbon it becomes steel. And 

 what a multitude of uses the very word suggests ; 



