them, or columns of spiral form were permitted no doubt on similar grounds; this, however, is inadmissible and opposed to the best taste, because the true function of the column is simply that of support, and to carry this out they ought to rise in a secure and straight line and be self-subsistent[94]. The only divergency from the rule in columnar structure which the ancients admitted was that of the groove, a variation which, as Vitruvius points out, made such appear broader than when their surface is wholly smooth. Such grooving we find carried out very extensively. I will now indicate more closely the main distinguishing features of the Doric, Ionian, and Corinthian order of columns respectively. (_α_) In primitive buildings _security_ of structure is the fundamental characteristic beyond which architecture fails to go; consequently it does not as yet dare to risk relations of a slender kind with the bolder lightness which belongs to them, but rests satisfied with forms of greater bulk. This is the case in the Doric type of building. We find here that the material aspect with its onerous weight still is that which is most influential, and is particularly apparent in the relations of breadth and height. When a building is erected in lightness and freedom the burden of heavy masses is overcome; if on the contrary its disposition is one which suggests mainly breadth and a low elevation the prevailing impression, as in the Doric style, is that of stability and solidity, subservient to the dominant force of gravity.