A TREATISE ON GAS-LIGHT.

15T

gas which passes through the whole range ofpipes sustains a pressure equal to the perpen-dicular weight of about one inch of water only,and such a weight of course is insufficient toburst iron pipes. Nor could the town whenilluminated by gas-lights, be thrown suddenlyinto darkness, as has been asserted might hap-pen by the fracture of a main pipe, supposingsuch an event should take place ; because thelateral branches, which supply the street-lampsand houses, are supplied by more than onemain; and the consequence of a fracturewould be only an extinction of the few lampsin the immediate vicinity of the broken pipe,because the rest of the pipes, situated beyondthe fracture, would continue to be suppliedwith gas from the other mains, as will becomeobvious from the sketch exhibited in the next