23

C—lA

Fig. 2 Plan

Fig, 2.—Ranging between Two Blocks not intervisible. 1, 4. Standard blocks. 3. Position of second set-up. 2. Position of first set-up. 5, 0. Pegs on line.

Fig. 3. —Grade-rod to enable Angles of Elevation and Depression between Tables to be read.

1. Rod about 5 ft. long. 2. Sighting-signal, adjustable to height of instrument. 3. Brass foot to stand on top of chaining-table. Fig. 4. —Showing Laying-out or Offset Lines in Towns. 1, 2. Standard blocks. 3. Offset pegs at right angles to standard lines, the lines between being parallel to standard lines and as nearly as possible 5 Jinks from line of occupation. Note.—The standard lines are measured first, and offset pegs put in. Those lines are then measured as carefully as the main lines and offsets taken. Three measurements are thus obtained for each standard line without check chainage. Occupation-points are taken with 10 links offset rod. Fig. 5.—Background fob Sighting-vane. 1. Flagpole. 4. Diamond-shaped black-cloth screen. 2. Hook. 5. Cross-arm pivoted in centre to flagpole. 3. Brass rings sewn on black-cloth screen. Fig. 6.—Chaining, and Sighting-tkipod Head. 1. Sighting-vane (may bo replaced by 9). 7. Shifting-head. 2. Socket for above. 8. Lugs with bolts and nuts to attach to tripod-legs. 3. Horizontal plate on which level is placed. 9. Chaining-plug (in place of vane). 4. Clamping-screw for ball. 10. Ball cut out to receive plummet-string hook from 5. Clamping-plate for ball. centre. 6. Clamping-screw lor shifting-head. 11. Plummet-string hook.