3. Tables of Work of Men.-Explanation of Table I. :-P, effort, lbs.; V, velocity, feet per second; T, hours' work per day; P V, work, foot-lbs. per second; 3,600 P V T, work, foot-lbs. per day. I.-WORK OF A MAN AGAINST KNOWN RESISTANCES. lbs. Explanation of Table II. :-L, load conveyed horizontally, lbs. ; V, velocity, feet per second; T, hours' work per day; L V, conveyed horizontally one foot in a second; 3,600 L V T, lbs. conveyed horizontally one foot in a day. III. DAY'S WORK OF A MAN REQUIRED FOR VARIOUS Shovelling earth, one cubic yard, thrown not ........ from 05 to 0625 '06 to '08 *025 to 2 Excavating earth with the pick, one cubic ing,* 05 to 0625 دو وو '3 4 *45 ....average Jumping holes in rock, 100 cylindrical inches, granite, do., limestone, Driving mines in rock; dimensions from 31⁄2 feet × 3 feet to 3 feet × 5 feet; one foot forward,.... Quarrying rock in tunnels, one cubic yard,... Making one thousand bricks,...... {men's time, time, Mixing mortar by hand, one cubic yard,... Mixing concrete, wheeling and laying, one cubic yard,. Loading barrows with stone, one cubic yard,... Wheeling one cubic yard of stone 100 feet horizontally; if on an ascent, allow 6 feet of distance for each foot of rise,.... Unloading barrows of stone, one cubic yard,.... وو * Weight of rock loosened÷weight of powder exploded in small blasts from 7,000 to 14,000; average 10,000: in great blasts from 4,500 to 13,000; average between 6,000 and 7,000. One lb. of blasting powder fills about 38 cylindrical inches. If gun-cotton be used instead of powder, allow one-sixth of the weight and one-half of the space. 30 cubic inches hard limestone, marble, granite soft sandstone x from 3 to 4. Facing ashlar (soft sandstone), per square footstroked, 05; droved, '07; polished, ·1. Taking down old masonry, one cubic yard, from 5 to 6. Brickwork, ordinary, one cubic yard,....... 6 Sinking cylinders for foundations under water with compressed air; foot, per inch diameter, per cubic yard of earth removed,......... Bricklayer. Labourer. .67 Shaping timber; pine-woods; one cubic Planing pine woods, per square foot, '02 *03 Supply of air should be at the rate of 30 cubic feet per man per minute. Erecting centres for arches; per 100 f from 1*55 square feet area of soffit,. Rivetting iron ships; from 100 to 1407) rivets,.. Making plank roads; breadth planked, 8 feet; total breadth, 16 feet; 1 lineal foot,........ I to... 1.70 *75 •80 PART VIII. HYDRAULICS. SECTION I.-RULES RELATING TO THE FLOW OF WATER. 1. Head of Water.-RULE I.-To find the head of a particle of water; add together the head of elevation, or height of the particle above some fixed or "datum" level, and the head of pressure, or intensity of the pressure exerted by the particle expressed as the height of an equivalent column of water. (See pages 103, 115.) In stating the pressure, it is usual not to include the atmospheric pressure; so that the absolute pressure exceeds the pressure stated in the common way by one atmosphere. When the absolute pressure is equal to the atmospheric pressure, the pressure stated in the common way is = 0; when the absolute pressure falls short of the atmospheric pressure, their difference is called vacuum. The atmospheric pressure, at the level of the sea, varies from about 32 to 35 feet of water, and diminishes nearly at the rate of 1-100th part of itself for each 262 feet of elevation. In the rest of this Section, heads in feet of water will be denoted by h. 2. Volume and Velocity of Flow.-RULE II.-To find the volume of flow of a stream; multiply the mean velocity by the sectional area. RULE III. To find the mean velocity of flow of a stream; divide the volume of flow by the sectional area. RULE IV. In a stream like a river channel the ratio of the mean velocity to the greatest velocity (which occurs at the middle of the stream) is nearly = greatest velocity + 7.71 feet per second greatest velocity + 10.28 feet per second The least velocity, being that of the particles in contact with the bed, is nearly as much less than the mean velocity as the greatest velocity is greater than the mean. In ordinary currents the least, mean, and greatest velocities are nearly as 3:4:5; in very slow currents, as 23: 4. In what follows, volume of flow in cubic feet per second will be denoted by Q; the mean velocity of a stream in feet per second |