Lb. per sq. in. 
Gileppe (Verviers).          88
Furens (St. Etienne).        93
Puentes.                    112
De Ban.                     113
St. Chamond.                114
Alicante.                   154
Hamiz (Algeria)—­failed.    157
Habra (Algeria)—­failed.    185

A diagram comparing the section derived from Molesworth’s formula and those of Furens, Gileppe, Vyrnwy, and Quaker Bridge, is given at Fig. 20, the limit of pressure assumed for the masonry being 93 lb. per square inch, which is that of the Furens, the Gileppe being 88.

* * * * *

NEW DREDGING MACHINERY.

We illustrate the new dredger Ajax, recently built for Mr. Geo. F. Smith, of Stockton, Cal.

The dredger has now been working for two weeks at Wakefield, and, we are informed, is giving entire satisfaction; having been repeatedly timed to be discharging clay at the rate of 220 cubic yards per hour.

[Illustration:  The new dredger Ajax.]

The Ajax is almost a duplicate of the last dredger designed by Mr. Ferris for levee building on Roberts Island, with such modifications and improvements as have suggested themselves in the two years it has been working.

The hull, oval in plan, is 36 ft. 10 in. by 60 ft. over all; it has four solid fore and aft bulkheads, and a well hole 5 x 12 ft. at one end for the bucket ladder.

The main engine is 10 x 24, operating, by bevel gearing and a 31/2 in. vertical shaft, a 4 sided upper tumbler with 21 in. sides.  This engine works also a gypsy shaft for swinging, and the conveyer that carries the mud ashore.  A steam hoist with 6 x 11 engines raises and lowers the bucket ladder.  The buckets, at 4 foot centers, have a struck capacity of 5 cubic feet, and are speeded to deliver from 18 to 20 a minute, according to the character of the material being handled.  They are of boiler iron, with a 5 in. steel nosing.  The links are of wrought iron, with cast bushings.  The lower tumbler is hexagonal, on a 4 in. shaft.

The conveyer, projecting 72 ft. from the center of the boat, consists of a 5 ply rubber belt 36 in. wide; running over iron drums at each end and intermediate iron friction rollers at 3 foot centers.  Ratchet and pinion on each side of conveyer ladder give means for taking up the slack of the belt and adjusting the drums to maintain them parallel.

This conveyer is the important feature of the dredge.  It is entirely satisfactory in its working and delivers its material, as nearly as may be, in a dry state upon the levee.  It was feared the rubber belt would be shortlived, but a 4 ply belt ran continuously for over two years on the Roberts Island dredge before it needed replacing.

The boiler is of the marine type, 52 in. by 10 ft. 6 in., with 3 in. tubes and 14 in. flues; and burns about 1,400 lb. of steam coal in a day of 12 hours.  There are three pumps aboard—­a hand force pump for washing boiler, a plunger pump for boiler feed, and an Evans steam pump to throw a jet of water into the delivery hopper when digging in any very tenacious material.  All three are connected with the boiler.