These centers covered two filters, each having an area of 121⅓×258 ft. There were six more filters of the same size, for which the same centers were used. The cost of taking down, moving and putting up these centers (313 M.) three times was as follows:
| Foreman, 2,359 hrs. at 35 cts. | $825.65 |
| Carpenters, 12,766 hrs. at 22½ cts. | 2,872.35 |
| Laborers, 24,062 hrs. at 15 cts. | 3,609.30 |
| Team, 430 hrs. at 40 cts. | 172.00 |
| 3,000 ft. B. M. lumber, at $20 | 60.00 |
| 3,000 lbs. nails, at 3 cts. | 90.00 |
| ———— | |
| Total cost of moving centers to cover 196,660 sq. ft. | $7,629.30 |
Fig. 287.—Forms for Constructing Grain Elevator Bins.
The cost of moving the centers each time was $8.10 per M., showing that they were practically rebuilt; for the first building of the centers, as above shown, cost only $6.37 per M. In other words, the centers were not designed so as to be moved in sections as they should have been. Although the centers were used four times in all, the lumber was in fit condition for further use. The cost of the labor and lumber for the building and moving of these centers for the 8 filter beds, having a total area of 259,220 sq. ft., was $15,438, or 6 cts. per sq. ft.
GRAIN ELEVATOR BINS.—In constructing cylindrical bins 30 ft. in diameter and 90 ft. high for a grain elevator the forms shown by Fig. 287 were used. For the inside wall a complete ring of lagging 4 ft. high nailed to circular horizontal ribs of 2×8-in. planks was used. For the outside wall two, three or four segments fitting the clear spaces between adjoining tanks were used, these panel segments being also 4 ft. high. The inside and outside rings were held together by yokes constructed as shown, and bolted to the inner and outer ribs. A staging built up inside the tank carried jack screws, on which were seated the inner legs of the yokes.