2 USEFUL MEMORANDA AND HINTS. 
TO MEASURE HEIGHTS WITH THE SEXTANT. 
jane ey Angie. Diyisor.| Angle. 
fe) 
1 45 0 1 45 0 
2 63 26 2 26 34 
3 71 34 3 18 26 
4 75 58 4 14 2 
5 78 41 5 11 19 
6 80 32 6 9 28 
8 82 52 Jt8 on8 
10 84 17 10 5 43 
Set the sextant to any angle in the table, and the height will equal the dis- 
tance multiplied or divided, as the case may be by the number opposite to: it. 
RAINFALM. 
Inches of rain-fall } 2,323,200 — cube feet per square mile. 
” ” »4 144 — millions of gals. per ditto. 
99 ” 8630 = cube feet per acre. 
\ 
HINTS ON THE| CONSTRUCTION OF CARRIAGE ROADS. 
Ordinary turnpike roads, 30 feet wide, the centre 6 inches higher than the sides, 
A feet from the centre 4+ inch below the centre, 
9 feet from the centre 2 ,, do. do. 
15 feet from the centre 6 ,, do. do. 
Footpaths 6 feet wide, inclined 1 inch towards the road: 
Side drains 3 feet below the surface of the road. 
Roap MarEriaLt: bottom layer gravel, burnt clay, or chalk, 8inches deep. Top layer, 
‘broken granite not larger than 1% inch cube, 6 inches deep. 
FoorpatHs—fine gravel, or sifted quarry chippings, 3 ities thick: 
WEIGHT OF EARTHS, ROCKS, &c. 
Weight of Cube yard of Sand about 30 Cwt.; Gravel do. 30 do; Mud do. 25 
do; Marl do. 26 do; Clay do. 31 do; Chalk do. 36do; Sandstone do. 89 do; Shale 
do. 40 do; Quartz do. 41 do; Granite do. 42 do; Trap da. 42 do; Slate do 43 do. 
Morrar—1 of lime to 3 or 33 of sharp river sand. 
Or, 1 of lime to 2 of sandand1 of blacksmith’s ashes or coarsely ground coke, 
CoarsE Mortar—l of lime to 4 of coarse gravelly sand. 
CONCRETE—1 of lime to 4 of gravel and 2 of sand. 
Hypravutic Mortar—l of the bluelias lime to 23 of burnt clay ground together. 
Or, 1 of blue lias lime to 6 of sharp sand, 1 of puzzolana and 1 of. ealeined 
ironstone, 
BetTon—1 of hydraulic mortar to 13 of angular stones. 
CEMENT—1 of sand io 1 of cement. If ereat tenacity is required the cement 
Should be used without sand. 
WaTERPROOF Mastic Cement—1 of red lead to 5 of ground lime and 5 of 
sharp sand, mixed with boiled oil, 
