To obviate all the difficulties and complications arising out of this constant breaking up of streets, with the attendant inconvenience to the public and damage to the surfaces of the roadways, it was suggested many years ago that subways should be constructed under the surface of the principal streets, in which should be placed all the gas and water mains then existing. There is no doubt that there are many advantages in this plan as well as some disadvantages. It must be recollected that probably the subways would have been constructed of sufficient capability to carry all the mains and wires then existing, with a margin for future extensions of size, but when we see the enormous growth of many towns, notably that of the metropolis, and the consequent increase necessary in the number and diameters of the mains, it is to be feared that sufficient space would not have been left, and competition between rival gas and water companies might consequently have been crippled. Still there would be great convenience in many respects if all water and gas mains, telegraph and telephone wires could be carried in subways, as they would be easily accessible for repairs, and hidden leaks would be unknown. With regard to the one great objection so constantly urged, that in the case of a leaky gas main or service a most terrible and damaging explosion might take place, it is true that this is a very grave and serious objection, but it must also be recollected that although this danger may be enhanced by the necessarily solid masonry of which the subway is constructed, still there would be every precaution taken to prevent leakage of gas, and in the present system liability to explosion is not altogether remote. In Percy Street, Tottenham Court Road, only a year or two ago, there was a terrible explosion in trenches and mains which had become full of gas and atmospheric air in the proportions of one volume of gas to fifteen volumes of air, and if gas mains were laid in subways greater precautions would no doubt be taken. There would be also great danger in conveying the wires used for electric lighting purposes in these subways, as they might fuse and thus cause danger, and at all events they would have some considerably disturbing influence upon the wires of the telegraph and telephone systems, if laid too near. I will now pass on to consider the powers of individuals to break the surface of public streets for the purpose of putting new drains to their premises or of repairing existing drains. With regard to the former question I have given full particulars with regard to new drains or connections with sewers in the chapter upon “house drainage,” but with regard to the latter question it will be necessary to make a few remarks.