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Neither natural nor manufactured gas contains any element or compound that is not contained in coal, but these gases are usually free from some obnoxious compounds found in coal or generated in the combustion of coal, such as phosphoric acid and sulphydric acid.

The waste products of the combustion of gas, however, should not be permitted to escape in the room. A hood placed over and a short distance above the gas stove, and attached to a flue or chimney with a fairly good draft will not only carry off the burnt gases, but also the odors rising from the meats and vegetables that are being cooked.

Gas is an economical fuel with which to cook, for two reasons; first, all expense for fuel will cease the instant the cooking is completed, and second, in the matter of roasting. There is a much smaller percentage of was'e in meat roasted in a properly constructed gas stove than occurs in the best stoves using solid fuel. A great number of experiments made a few years age in London by a committee of experts demonstrated that meat roasted by the best gas roasters lost but ten to eleven per cent. of weight, that is, the cooked meat weighed ten to eleven per cent. less than did the raw meat, while with coal heated stoves the loss in meat ranged from twenty to twenty-five per cent. This last item alone would go a long way toward paying the additional cost of gas over coal, if in fact, any additional cost occurs. Natural gas, as it is usually sold, of course, is very much cheaper for cooking purposes than any solid fuel can be.

For domestic heating, the warming of residences, natural gas has no equal, barring possibly the slight element of danger attending its use.

There are devices now in use that automatically turn on and off the gas, so as to maintain the temperature at any desired degree. These devices are so sensitive that a change of one degree in temperature will be sufficient to cause them to turn off or put on more gas, as may be required to maintain an equable temperature and when set to maintain the temperature of a room at 70 degrees Fahr., will prevent the temperature of that room falling below 69 or rising above 70 degrees.

MEASUREMENT OF GAS-WELLS AND OTHER GAS-STREAMS, AND THE PIPING OF NATURAL GAS.

COLUMBUS, O., June 10, 1886.

DR. EDWARD ORTON, State Geologist of Ohio:

DEAR SIR: I respectfully give below the results of the investigation requested by you, of means most feasible for measuring the discharge of gas-wells.

Sincerely yours,

S. W. ROBINSON.

CHAPTER IX.

MEASUREMENT OF GAS WELLS AND OTHER GAS STREAMS, AND THE PIPING OF NATURAL GAS.

BY PROF. S. W. ROBINSON, OHIO STATE UNIVERSITY.

I. GAS-WELLS.

Some of the recently bored gas-wells in Ohio are discharging gas at too high a rate to be measured conveniently with an ordinary gas anemometer, since the delicacy of the instrument is such that it cannot stand the violence of the current. To use it would require reduction of velocity by increasing the diameter of the stream of flowing gas from the well. This may be done by means of flaring tubes fastened to the well-mouth, which, however, is attended with some cost and trouble, the avoidance of which is desirable. To this end I was invited by the State Geologist, Dr. Edward Orton, to consider the question of gas-well measurement.

The correct measurement of such a gas stream, where the temperature, density and velocity are all unknown, appeared to be a matter of considerable difficulty, even when the anemometer could be applied, because that instrument could make known only one of the unknown quantities, viz., the velocity. The density being still unknown, the weight of gas discharged per minute could not be determined; and as the wellmouth temperature is also still unknown, the density at that temperature cannot be calculated, even if the specific gravity of the gas is known.

Among the various appliances which suggested themselves for application was the Pitot's tube, a shunt, Bunsen's effusion principle for density of shunted gas, and a thermometer enclosed in an open tube, nearly closed at the rear, to be presented as is the Pitot's tube.

On investigation, the Pitot's tube was found to give the value of the product of the density by the square of the velocity. Had it given the density and velocity both to the same exponent in the product, the weight per second could have been found by simply multiplying by the area of the well-mouth; but that not being the case, it was necessary to find the density, or the specific gravity which will serve as well, in the well-mouth, either directly or calculate it from that of the gas at ordinary conditions. Measuring the velocity by the anemometer would serve, but the use of this instrument was what was to be avoided. By using the shunt of known area of mouth, and storing the gas for a definite time of flow through the shunt, the gas being allowed to gain ordinary conditions, the weight or volume per second for the well could be found from the shunt alone by multiplying the weight or volume per second shunted by the ratio of areas of well-mouth and shuntmouth.

This shunt device was therefore considered favorably, until some experimental measures were made. But the testing of the devices showed that the shunt could not be relied upon generally, for the reason that the gas sometimes carries oil from the well, which oil would smut the shunt orifice and modify to an unknown degree, the effective area of the shunt-mouth, and correspondingly vitiate the results in such cases. In the Pitot's tube tests the instrument was found to be thoroughly reliable for what it gave, regardless of the heterogeneity of the fluid flowing; and the temperature of the gas could be estimated with some degree of approximation, since the pipes would sometimes freeze the water condensed upon them and sometimes not, at all the wells examined during the testing of the instruments. Also, the Pitot's tube, for convenience of application cannot be excelled, as the completion of an observation is but the work of a moment, regardless of condition of orifice. The encased thermometer was not applied at gas-wells, though it has been well tested in connection with Westinghouse air apparatus.

As all these appliances will doubtless be found useful in the measurement of the streams of gas from gas-wells, and of other gas currents, a description of each and the formulas for reduction of observations wi'l be given.

THE PITOT'S TUBE.

This tube takes its name from the inventor, Pitot, who made it known to the French Academy of Sciences in 1732. (See Morin's "Hydraulics," page 131.) It is shown in all its simplicity and essential principles in fig. 1, in position for determining the velocity of a current of water flowing along its bed with the free surface at b. The instrument, as here shown, consists simply of a plain piece of glass tube, L shaped, placed with an open mouth, a, presented directly toward the current, while the other end reaches above the surface at b. Now, when the water drives against the open end a, a pressure results from the impact, which causes the water to rise in the branch be, to a height h, which height is to be used as a head by which, in some way, to calculate the velocity. Pitot concluded that this head was simply that due to the volocity v of the current, so that v2 = 2gh, where g is the acceleration of gravity. This formula is that for falling bodies, and also that for Torricelli's theorem for the velocity of issue of water from an orifice.

According to this, when water is flowing from an opening in the side of a tank, if the mouth of the Pitot's tube, somewhat smaller than the jet, be presented square against the jet, the water would rise in the upright branch of the tube just to the level of the surface of the water in the tank. This simple device, therefore, furnishes us a very handy means for finding the velocity in a stream of water, provided the instrument is reliable for accuracy.

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For over one hundred years after its discovery, this device, so admirable for its simplicity, was regarded more for curiosity than utility, and it was believed not to be reliable for accuracy. (See D'Aubuisson's "Hydraulics" (Bennett's translation), page 158.) But about 1850, М. D'Arcy, an able French hydraulic engineer, seeing in the Pitot's tube the rudiments of a most admirable hydraulic instrumen', studied it with a view to reducing it to the most useful form and design for practical purposes, for a complete description of which, see Morin's "Hydraulique," page 133. The main features of this form consist of using two tubes side by side, extending from some distance above water down to desired depth, then turning horizontally toward the current to where one tube terminated in a small mouth of one millimeter diameter presented direct, while the second tube was cut to a long slant and was joined upon the side of the first so as to form a smooth and converging exterior surface. Near the front termination of the second tube and

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