than ourselves had sufficient faith in the continuity of the gas supply to offer to furnish us with gas for a sum per year equal to that hitherto annually paid for coal until the amount expended by them on piping had been repaid, and afterward at half that sum. It took us about eighteen months to recoup the gas company, and we are now working under the permanent arrangement of one-half the previous cost of fuel on cars at work. Since our success in the use of this new natural fuel at the rail mills, parties still bolder have invested in lines of piping to the city of Pittsburg, fifteen to eighteen miles from the wells. The territory underlain with this natural gas has not yet been clearly defined. At the principal field, that of Murraysville (from which most of the gas is obtained to-day), I found, upon my visit to that interesting region last autumn, that nine wells had been sunk, and were yielding gas in large quantities. One of these was estimated as yielding 30,000,000 cubic feet in 24 hours. This district lies to the northeast of Pittsburg, running southward from it toward the Pennsylvania Railroad. Gas has been found upon a belt averaging about half a mile in width for a distance of between four and five miles. Beyond that again we reach a point where salt water flows into the wells and drowns the gas. Several wells have been bored upon this belt near the Pennsylvania Railroad, and have been found useless from this cause. Geologists tell us that in this region a depression of 600 feet occurs in the strata, but how far the fault extends has not yet been ascertained. Wells will no doubt soon be sunk southward of the Pennsylvania Railroad upon this half-mile belt. Swinging round toward the southwest, and about twenty miles from the city, we reach the gas fields of Washington county. The wells so far struck do not appear to be as strong as those of the Murraysville district, but it is possible that wells equally productive may be found there hereafter. There are now four wells yielding gas in the district, and others are being drilled. Passing still further to the west, we reach another gas territory, from which manufacturing works in Beaver Falls and Rochester, some twenty-eight miles west of Pittsburg, receive their supply. Proceeding with the circle we are drawing in imagination around Pittsburg, we pass from the west to the southwest without finding gas in any considerable quantity, until we reach the Butler gas field, equidistant from Pittsburg on the northwest, with Washington county wells on the southwest. Proceeding now from the Butler field to the Allegheny River, we reach the Tarentum district, still about twenty miles from Pittsburg, which is supplying a considerable portion of the gas used. Drawing thus a circle around Pittsburg, with a radius of fifteen to twenty miles, we find four distinct gas-producing districts. In the city of Pittsburg itself several wells have been bored; but the fault before