1216

THEORY AND PRACTICE OF ENGINEERING.

Book II.

Four 2^ inch stand-pipe, with 40 feet of hose, and J inch jet, rose 35 feet.

Five 2} — 40 — 1 — 30

Six 2$ — 40 — | — 27

All the fire-plugs on the main were then closed, except the first, and one 2^-inch stand-

pipe with 160 feet of hose and J-inch jet, rose 40 feet. 'Die quantity of water deliveredtroin the same main, through one stand-pipe, and different lengths of hose, was as follows,viz : —

One 2\ inch pipe, 40 feet of hose, | inch jet, delivered 96 gallons in 59 seconds.

2j — 80 — l — 112 — 65

25~160 — | — 116 — 70

2^ — 40 — 2J — 118 — 27

The second trial in Tooley Street, of a 9-inch main, 1400 yards in length, connected to1000 yards of 15-inch, and 6650 yards from the works.

One 2.5 inch-stand pipe, 40 feet of hose, | inch jet, rose 60 feet.

T wo 2£ — 40 — l difference not perceptible.

Four 2 : ^ — 40 — | rose 45 feet.

Six 2£ — 40 — l — 40

Quantity delivered from the same main trough.

One inch stand-pipe, 40 feet of hose, \ inch jet, 114 gallons in 64 seconds.

Four 2^ — 40 — g — 115 — 75

Six 2^ — 40 — l — 112 — 78

Four-inch service in Tooley Street, 200 yards long, supplied through 200 yards of 5-inchpipe, from 9-inch main, one 2±-inch stand-pipe fixed on the 4-inch service, near the 5-inchpipe, with 40 feet of hose, |-inch jet, rose 40 feet. Two 2.^-incli stand-pipes, |-inch jets, rose31 feet.

One 2^-inch stand-pipe fixed at the end of service, 200 yards from 5-inch pipe, 40 feet ofhose, §-ineh jet, rose 34 feet.

Quantity delivered from the plug near the 5-inch main, through

One 2i inch stand-pipe, 40 feet of hose, £ inch jet, 112 gallons in 82 seconds.

Two 2 j — 40 — | — 117 — 103

Quantity from end of plug of service 200 yards, from the 5-inch main.

One 2£ inch stand-pipe, 40 feet of hose, g inch jet, 112 gallons in 90 seconds.

Two 2^ — 40 — | — 114 — 118

It is also stated that water will rise higher from a hose attached to a fire-plug in thestreet, at the extreme point of the delivery, in the night than in the day-time, and thatwhen water is in motion, there will be friction in the main pipes, by which the height towhich it rises is diminished. The higher the water is thrown on a pipe, or the higher thenozzle of a hose-pipe is carried, the more the resistance of the atmosphere is avoided : if a jetacting under a pressure of 100 feet attained an elevation of 50 feet when discharged fromthe level of the pavement, and the hose pipe were elevated to the height of 50 feet, a jetwould be given probably from 20 to 25 feet in height : by this means, the water wouldattain an elevation of 70 or 75 feet, instead of 50 ; hence the advantage of carrying a hose-pipe up stairs or on a ladder, or as nearly as possible to the height of the story, when afire occurs.

CHAP. XIX.

ATMOSPHERE AS A MOVING POTVER.

Is the year 1667 Dr. Croune laid before the Royal Society the first instrument contrivedfor measuring the force of the wind ; consisting of a fan included within a cylindricalvessel, which was divided into 32 equal parts, each having a narrow slit, through which theair might pass: this imperfect machine was afterwards improved by Dr. Hooke, and others,and several very ingenious anemometers are now made use of, by which both the forceand velocity of the wind may be ascertained. The weight or pressure of the atmosphereis shown by the sucking pump, sustaining a column of water, or the barometer by acolumn of mercury which is exactly equal in weight to a cylinder of air of equal diameter,reaching to the top of the atmosphere. The mean height of the barometer at the level ofthe sea is about 28*6 inches, and 1 cubic inch of mercury weighs 3425*92 grains, or 0-48956pounds avoirdupois; so that a column of mercury whose base is a square inch, and havingthe mean height of the barometer, weighs 0*48956 x 28*6= 14*6 lbs. avoirdupois, which is