six standcocks being opened, the first jet was further
reduced to 40 feet high, and the delivery to 76 gallons per minute.

_3rd Experiment._--Two standcocks, with hose, &c., as in the first
experiment, were then put into a service-pipe, 4 inches diameter and
200 yards long, in Tooley-street, the service-pipe was connected with
200 yards of main 5 inches diameter, branching from the main of 9
inches diameter. The weather was still the same as at first, but the
wind did not appear to affect the jets, owing to the buildings all
round being so much higher than the jet.

1st. The standcock nearest the larger main was opened, and a jet of 40
feet high was produced, delivering 82 gallons per minute.

2nd. Both standcocks being opened, the first gave a jet of 31 feet,
and delivered 68 gallons per minute.

3rd. The standcock farthest from the large main only being opened,
gave a jet of 34 feet, and delivered 74 gallons per minute.

4th. Both standcocks being opened, the farthest one gave a jet of 23
feet, and delivered 58 gallons per minute.

When both these plugs were allowed to flow freely without hose, the
water from that nearest the large main, rose about 18 inches, and the
farther one about 1 inch above the plug-box.

[Illustration: FIG. 7. Common Fire-plug.]

These and other experiments prove the necessity of placing the plugs
on the mains, and not on the service pipes, where there are mains in
the street.

The different modes of obtaining water from the mains or pipes are
shown in the accompanying drawings.

(Fig. 7) is a section of a common plug when not in use.

[Illustration: FIG. 8. Fire-plug with canvas cistern.]

(Fig. 8) is a section of the common plug, with a canvas dam or cistern
over it, as used in London. The cistern is made of No. 1 canvas, 15
inches deep, extended at top and bottom by 5/8-inch round iron frames,
a double stay is hinged on the top frame at each end. When the cistern
is used the top frame is lifted up, and the stays put into the
notches, in two pieces of hoop iron, fixed to the bottom frame. There
is a circular opening 9 inches diameter in the canvas bottom, two
circular rings of wash-leather, about 2 inches broad, are attached to
the edges of the opening in the canvas, so as to contract it to 4
inches or 5 inches diameter; the plug being opened, the cistern is
placed over it; the wash-leather is pressed down to the surface of the
road by the water, and a tolerably water-tight c