means of settling this except to design the shaft in both ways and compute the costs. Even then it may not be economics but aesthetics which will govern the decision, because the reinforced-concrete piers are liable to lack the massive appearance which is necessary for a pleasing effect. Unless there be some really-material advantage in reinforcing the shafts, it is generally better to build them of plain concrete.

There is an economic expedient in pier designing that is very often perfectly legitimate, especially in small structures and occasionally in very large ones, viz., the use of the "dumb-bell" cross-section, or, in other words, adopting two pedestals with a diaphragm wall between. This wall may either rest on a continuous base or may be entirely unsupported between the pedestal bases, thus acting as both a strut and a beam. The appearance of a structure having piers of this type is not unpleasing, and the effect of massiveness is obtained by the expenditure of very little extra material. In a wide, two-truss bridge, solitary pedestals without a connecting wall may be employed, reliance being placed upon: the end floor-beams of the spans to divide the wind load about equally between the two supports. In case that the deck is fairly close to the water, the great width will partially hide the substructure, and the lack of the connecting wall will not be noticed; but in a high-level bridge, especially when carrying railroad trains, pedestal shafts not only produce a flimsy appearance but also fail to resist properly the rack from the live load. The Missouri River bridge at Glasgow was originally built in that manner; and the experience with its piers was so unsatisfactory that the twin pedestals had to be removed and replaced by a solid shaft.

In some cases it is essential that the load on the foundations be reduced to an absolute minimum, and to this end hollow shafts, or pedestals connected by two thin walls, may he employed; and the excavating shafts in the bases need riot be filled, excepting only sufficiently at the bottom to transfer properly the upward thrust of the foundation into the solid portions of the base.

Tall steel cylinders filled with concrete and well braced between make an economical substructure for light highway bridges; and this type of construction is proper, provided that the cylinders be carried far enough down into fairly-hard material to hold firmly the lower ends, so as to enable the cylinders to act as beams with fixed ends for resisting the bending effects of wind loads and traction loads. Generally in such cases it will be found necessary to build a substantial mattress around each pier, so as to prevent the scouring out of the material upon which reliance is being placed for fixing the ends.

Temporary piers of timber, such as those built by the author in the middle nineties for the Missouri River bridge between Council Bluffs, Iowa, and East Omaha, Nebraska, are a legitimate economic expedient, provided that due arrangement be made for replacing them later by permanent piers without involving any unnecessary expense or interrupting