I went up to the gas-fields of northern Ohio in company with Prof. Edward Orton, the State Geologist, who has made a study of the subject, and pretty well defined the fields of Indiana and Ohio. The gas is found at a depth of between 1100 and 1200 feet, after passing through a great body of shale and encountering salt-water, in a porous Trenton limestone. The drilling and tubing enter this limestone several feet to get a good holding. This porous limestone holds the gas like a sponge, and it rushes forth with tremendous force when released. It is now well settled that these are reservoirs of gas that are tapped, and not sources of perpetual supply by constant manufacture. How large the supply may be in any case cannot be told, but there is a limit to it. It can be exhausted, like a vein of coal. But the fields are so large, both in Indiana and Ohio, that it seems probable that by sinking new wells the supply will be continued for a long time. The evidence that it is not inexhaustible in any one well is that in all in which the flow of gas has been tested at intervals the force of pressure is found to diminish. For months after the discovery the wells were allowed to run to waste, and billions of feet of gas were lost. A better economy now prevails, and this wastefulness is stopped. The wells are all under control, and large groups of them are connected by common service-pipes. The region about Fostoria is organized under the North-western Gas Company, and controls a large territory. It supplies the city of Toledo, which uses no other fuel, through pipes thirty miles long, Fremont, and other towns. The loss per mile in transit through the pipes is now known, so that the distance can be calculated at which it will pay to send it. I believe that this is about fifty to sixty miles. The gas when it comes from the well is about the temperature of 32° Fahr., and the common pressure is 400 pounds to the square inch. The velocity with which it rushes, unchecked, from the pipe at the mouth of the well may be said to be about that of a minie-ball from an ordinary rifle. The Ohio area of gas is between 2000 and 3000 square miles. The claim for the Indiana area is that it is 20,000 square miles, but the geologists make it much less.