[Illustration: Fig. 14 - SOLE TILE.] Fig. 14 - SOLE TILE. One chief objection to the _Sole-tiles_ is, that, in the drying which they undergo, preparatory to the burning, the upper side is contracted, by the more rapid drying, and they often require to be trimmed off with a hatchet before they will form even tolerable joints; another is, that they cannot be laid with collars, which form a joint so perfect and so secure, that their use, in the smaller drains, should be considered indispensable. [Illustration: Fig. 15 - DOUBLE-SOLE TILE.] Fig. 15 - DOUBLE-SOLE TILE. The _double-sole tiles_, which can be laid either side up give a much better joint, but they are so heavy as to make the cost of transporation considerably greater. They are also open to the grave objection that they cannot be fitted with collars. Experience, in both public and private works in this country, and the cumulative testimony of English and French engineers, have demonstrated that the only tile which it is economical to use, is the _best_ that can be found, and that the best,—much the best—thus far invented, is the "pipe, or round tile, and collar,"—and these are unhesitatingly recommended for use in all cases. Round tiles of small sizes should not be laid without collars, as the ability to use these constitutes their chief advantage; holding them perfectly in place, preventing the rattling in of loose dirt in laying, and giving twice the space for the entrance of water at the joints. A chief advantage of the larger sizes is, that they may be laid on any side and thus made to fit closely. The usual sizes of these tiles are 1-1/4 inches, 2-1/4 inches, and 3-1/2 inches in interior diameter. Sections of the 2-1/4 inch make collars for the 1-1/4 inch, and sections of the 3-1/2 inch make collars for the 2-1/4 inch. The 3-1/2 inch size does not need collars, as it is easily secured in place, and is only used where the flow of water would be sufficient to wash out the slight quantity of foreign matters that might enter at the joints. [Illustration: Fig. 16 - ROUND TILE AND COLLAR, AND THE SAME AS LAID.] Fig. 16 - ROUND TILE AND COLLAR, AND THE SAME AS LAID.