And yet they were marvellous pioneers, these architects.

They had already succeeded in evolving out of the dark, as it were, a number of conceptions which, from the beginning no doubt, slumbered in mysterious germ in the human brain--the idea of rectitude, the straight line, the right angle, the vertical line, of which Nature furnishes no example, even symmetry, which, if you consider it well, is less explicable still.

They employed symmetry with a consummate mastery, understanding as well as we do all the effect that is to be obtained by the repetition of like objects placed _en pendant_ on either side of a portico or an avenue.

But they did not invent the vault.

And therefore, since there was a limit to the size of the stones which they were able to place flat like beams, they had recourse to this profusion of columns to support their stupendous ceilings.