feet and one to a depth of one hundred and twenty-two feet below extreme low water, and has encountered no trouble worth mentioning during the sinking. In the case of the greater depth, a mass of boulders was found overlying the bed-rock. This was penetrated as far as practicable by excavating the boulders and laying bare the bed-rock near the centre of the pier, then firing charges of dynamite at the bottom till the cylinder refused to sink any farther, after which it was filled up with concrete.

It is probable that, if one were to try to sink small piers to any great depth by the open-dredging-process, difficulty would be experienced because of the lack of sufficient weight of pier as compared with the large anoint of skin friction. The latter in sand is generally a little less than six hundred pounds per square foot of vertical surface. On the East Omaha bridge the author arranged to reduce this friction by means of small water-jets placed around the circumference of the cylinder about every six feet in height; but these were found to be unnecessary, so were not used. In case of striking clay or any other sticky substance, such an attachment might prove of great service.

The open-dredging process is liable to abuse by the builders of cheap highway bridges, who, in order to save a little in first cost, use it to sink cylinder piers of small diameter moderate distances to bed-rock, which may in these places be laid bare or nearly so by excessive scour. With this process it is generally not practicable to anchor the cylinders firmly to the bed rock, but with the pneumatic process it is.

There is still another style of foundation besides the three described, viz., that which involves the use of piles. These piles may either support a timber grillage, upon which to rest the pier proper, or may run up into the concrete body of the pier. This class of foundation is of a cheap order, but will often answer the purpose very well, provided these be no possibility of excessive scour. If the bearing capacity of the piles be small, it is best to spread them out and cover them with a thick timber grillage; but otherwise it will be found economical to run the piles up into the concrete.  The author