Comparing the heat given off by gas burnt in an ordinary gas-burner and that burnt in a Bunsen burner, Professor Lewes states that aluminous flat-flame burner gives a temperature of:-,462° P., and an ordinary Bunsen flame a temperature of 2,732° P., while by increasing the quantity of air until the flame is on the point of flashing down the tube the temperature rises to 2,966° P.; in ten experiments the amount of gas consumed is not stated. A Bunsen burner consuming 4 cub. it. per hour will require about 36 cub. ft. of air per hour, while the air would be contaminated to the same extent by both descriptions of burner, since the total a mount of gas burnt and consequently the products of combustion given off would be the same in both cases. When the gas is mixed with too much air it forms an explosive mixture. With regard to the proportioning of the gas and air supplies of Bunsen burners, the information on this point is mainly due tutbe labours of Mr. T. Fletcher, F.C.S., the well-known gas-stove maker of Warrington. In a paper read before a meeting of the Gas Institute in 1883, Mr. Fletcher states "that the mixing-tube [of a Bunsen burner if horizontal should not be less in length than four and a half times or more than six times its diameter." With regard to the diameter of the mixing-tube, " with large flames, given a certain size of gas jet, the diameter of the mixing-tube should not be less than ten times as great." " Given a certain area of tube delivering a combustible mixture, the outlet for this mixture must be neither more nor less than the size of the tube." " The variation from the rule, however, must be a matter of exparience with each form of burner.

There is also the fact that with small divide flames it is not necessary to mix so large a proportion of air, as each flame will take up air on its external surface; but in this case the flames are longer, hollow, and of lower temperature. As a matter of actual practice, where a burner is used which gives a number of separate flames or jets the diameter of the mixing tube does not need to exceed eight times the diameter of the gas jet. the remainder of the air required being taken up by the surfaces of the flames." It will be seen from the foregoing that it is advisable to regulate the air openings according to the quantity of gas passing.