The cost of material and labor at Lock No. 15 (10-ft. lift), which contains 2,559 cu. yds. of concrete, was as follows:

Materials.Per cu. yd.
0.56 bbl. Portland cement (0.96 per cu. yd.)$1.42
0.64 bbl. Utica cement (1.58 per cu. yd.).30
0.58 cu. yd. stone1.15
0.60 cu. yd. gravel.52
14 ft. B. M. lumber[F] at $15 per M..21
0.6 lb. spikes.01
Coal (10 tons in all, at $1.70).01
0.35 gal. kerosene.03
——
Total materials$3.65
Labor.
Erecting forms ($7 per M.).45
Removing forms ($2 per M.).13
Erecting and removing mixer ($161).06
Loading and unloading materials at yards and lock sites.23
Track laying ($86).03
Train service (narrow gage road).09
Delivering materials to mixer.28
Mixing concrete.11
Depositing concrete.21
Tamping concrete.21
Mixing, depositing and tamping, 69 cu. yds. face mortar ($160).23
General construction ($553).22
——
Total labor$2.25

[F] The lumber was used nearly five times, which accounts for its low cost per cu. yd.

There were 1,430 cu. yds. of Portland cement concrete. 69 cu. yds. of Portland cement mortar facing, and 1,059 cu. yds. of Utica cement concrete. The Portland concrete cost $6.43 per cu. yd.; the Utica concrete, $4.77 per cu. yd. The following is the cost of labor on Lock No. 20 (11-ft. lift.; 2,750 cu. yds.):

Per cu. yd.
Erecting forms ($7 per M.)$.434
Removing forms ($1.70 per M.).113
Erecting and removing mixer ($151).058
Loading and unloading at yards, lock sites, etc..614
Tracks.024
Train service (narrow gage).016
Pumping.114
Delivering material to mixer.288
Mixing concrete.134
Depositing concrete.205
Tamping concrete.192
Mixing, depositing and tamping, 85 cu. yds. face mortar.071
General construction.246
———
Total$2.509

COST OF HAND MIXING AND PLACING, CANAL LOCK FOUNDATION.—Mr. Geo. P. Hawley gives the following record of mixing and placing 4,000 cu. yds. of 1-4½ gravel concrete for the foundation of a lock constructed for the Illinois and Mississippi Canal in 1897. The concrete was mixed on 14×16-ft. board platforms, from which it was shoveled directly into place. The materials were brought to the board in wheelbarrows. Two boards were used, the usual gang for each being 4 men wheeling gravel, 4 men mixing, 1 man sprinkling, 2 men depositing and leveling and 2 men tamping. The two gangs were worked against each other. Ten hours constituted a day's work, and the average time and cost per cubic yard for mixing and placing were:

Cts.
Foreman, 0.21 hr., at 30 cts6.30
Laborers, 3.339 hrs., at 15 cts50.09
Pump runner, 0.129 hr., at 20 cts3.58
Water boy, 0.087 hr., at 7½ cts0.65
——
Total labor per cu. yd., cents.60.62

BREAKWATER AT MARQUETTE, MICH.—The breakwater extends out from the shore and consists of a prism of concrete resting on timber cribs filled with stone. Originally the cribs carried a timber superstructure; this was removed to give place to the concrete work. A typical cross-section of the concrete prism is shown by Fig. 77; the prism is 23 ft. wide on the base. Farther in shore the base width was reduced to 20 ft., and in the shore section the prism was changed to a triangular trapezoid by continuing the first slope to the bottom cutting off the berm and second slope. The wooden structure was removed to a level 1 ft. below mean low water and on it a concrete footing approximately 2 ft. thick was constructed for the prism proper. This footing reached the full width of the crib and was constructed in various ways during the 5 years through which the work continued. At first the footing concrete was deposited loose under water by means of bottom dumping buckets; later the stone filling of the cribs was simply leveled up by depositing concrete in bags, and last toe and heel blocks were molded and set flush with the sides of the crib and filled between. Methods of construction and records of cost are reported for portions only of the work and these are given here.