9. The terrible operations of artillery, by which walls are broken down, towers are shattered, and armies are laid low, depend on nothing but the proper arrangement of materials, so that the active is placed in close connection with the passive element; that is to say, on the proper mixing of saltpetre with sulphur (the coldest substance with the hottest), on the proper construction of the cannon, on its being skilfully loaded with powder and missiles, and, lastly, on its being correctly pointed at the objects to be hit. If one of these conditions be not properly fulfilled, the whole apparatus is useless.
10. How is it that the processes of printing, by which books can be multiplied quickly, neatly, and correctly, are properly carried out? Assuredly by means of order. The type must be cut, moulded, and polished, placed suitably in the type-boxes, and then arranged in the right order, while the paper must be prepared, damped, stretched, and placed under the press.
11. To take another example of mechanism. How is it that a carriage, a construction of wood and iron, can be so easily drawn by the horses that are fastened to it, and can be of such use for the conveyance of men and burdens? This is brought about by nothing but the skilful arrangement of wood and of iron in the wheels, the axle-trees, and the shafts. If one of these parts give way, the whole construction is useless.
12. How is it that men can trust themselves to the stormy sea in a construction made of a few pieces of wood? How is it that they make their way to the antipodes and return safe and sound? It is nothing but the proper combination of keel, mast, rudder, compass, etc., in the ship that enables them to do so. If any one of these fail in its action, they are in great danger of shipwreck or of foundering.
13. Finally, how is it that the machine for measuring time, the clock, which is nothing but a well-arranged and well-devised disposition of iron parts, moves harmoniously and evenly, and marks off minutes, hours, days, months,
