The Classical Orders. From Wikipedia.org
Excerpts from Volume I of The Stones of Venice, by John Ruskin. London, 1896
All European architecture, bad and good, old and new, is derived from Greece through Rome, and coloured and perfected from the East. The history of Architecture is nothing but the tracing of the various modes and directions of this derivation. Understand this, once for all: if you hold fast this great connecting clue, you may string all the types of successive architectural inventions upon it like so many beads. The Doric and the Corinthian orders are the roots, the one of all Romanesque, massy-capitaled buildings –Norman, Lombard, Byzantine, and what else you can name of the kind; and the Corinthian of all Gothic, Early English, French, German, and Tuscan. Now observe: those old Greeks gave the shaft; Rome gave the arch; the Arabs pointed and foliated the arch.
I have said that the two orders, Doric and Corinthian, are the roots of all European architecture. You have, perhaps, heard of five orders: but there are only two real orders; and there never can be any more until doomsday. On one of these orders the ornament is convex: those are Doric, Norman, and what else you recollect of the kind. The transitional from, in which the ornamental line is straight, is the center or root of both. All other orders are varieties of these, or phantasms and grotesques, altogether indefinite in number and species.
This Greek architecture, then, with its two orders, was clumsily copied and varied by the Romans with no particular result, until they began to bring the arch into extensive practical service; except only that the Doric capital was spoiled in endeavours to mend it, and the Corinthian much varied and enriched with fanciful, and often very beautiful imagery. And in this state of things came Christianity: seized upon the arch as her own: decorated it, and delighted in it: invented a new Doric capital to replace the spoiled Roman one: and all over the Roman empire set to work, with such materials as were nearest at hand, to express and adorn herself as best she could. This Roman Christian architecture is the exact expression of the Christianity of the time, very fervid and beautiful.
Column orders. Fromhttp://www.cvilleindustries.com/