We notice that the absurdity of selling gas by measure merely without regard to its quality, to which we called atten tion in an article on Gas Measurement, nearly a year ago, has begun to attract notice both in this country and in Europe. Migineering, of April 9th. contains an able editorial on this subject, in which it almost reiterates the very language we used in the article referred to. It says : There seems to be a very general opinion on the part of gas consumers that they should have some readily accessible certification of the quality of gas in regard to illuminating power and purity; and that since the supply of this lighting material is virtually a monopoly, the relations between the price paid for it and the qualities above mentioned, should be regulated in such a manner that the consumer might obtain a fair equivalent for his money, while the gas companies would be secured a reasonable interest on the capital and expenditure necessary for their operations. It is evident that if the gas delivered to customers be of uniform chemical composition, and be delivered under uniform conditions of pressure, its illuminating power will be uniform. These conditions can be only approximated in practice, but there are certain limits beyond which no viftiation ought to be tolerated. A photometric test is one which ia out of the question for universal use. Beside requiring personal attention at every application, there is no unit of measurement that can be relied upon as being uniform. Candles vary widely in their illuminating power, and the oil lamp of Keates, recently invented for photometric use, seems to us far from perfect. There is also a necessity for the proper adjustment of burners to the quality of the gas in photometric tests. No test made with a single burner is reliable. Poor gas will flow far more freely through a small aperture than rich gas, and as the flow is intimately connected with the pressure, and the pressure with the illuminating power, the necessity for repeated tests with different burners becomes obvious. These considerations show that this kind of testing can never be made available to consumers at large. We believe a specific gravity test cannot be made applicable to the obtaining of approximate results as to the illuminating power, and the determination of ihose gases which are detrimental to the illuminating power -of the complex mixture of hydrocarbons which constitute illuminating gas. We speak of this here because it has-beefTproposed several times Of late, by inventors not fully acquainted with the subject, to construct a meter having a register to run faster or slower, as the specific gravity of the gas might vary. We consider such a device a useless one, as the specific gravity of gas beats but a slight relation to its illuminating power. Any method, to be of value to tlfe consumer, must be one that can be applied at will and give the mean illuminating power for the periods of time for which bills are made out and collected. The problem to be solved then is the invention of a means, either as an attachment to the ordinary meter or otherwise, whereby the mean illuminating power, per month or quarter, can be readily obtained by the consumer as well as the companies who supply the gas. This, with the quantity delivered and the mean pressure at which it has been delivered, would form an equitable basis for assessments. The determination of the mean pressure seems to us to be not a difficult thing to accomplish by some simple addition to the meter itself. The determination of the mean illuminating power is by far more difficult to accomplish by the use of mechanism. It does not seem impossible, however, to collect a specimen of gas by means of simple mechanism, that shall be a sample of the mean quality of the gas used during a given space of time. But how shall this specimen be tested when obtained? There is loom here for a good deal of study. It is possible that a fixed relation may be found between the illuminating power of gas and its heating power; if so, the test would be exceedingly simple, but we see reasons that lead us to suppose such a relation would be difficult to establish. Notwithstanding the difficulties of this problem, we believe its solution is possible and that some inventor will yet realize a fortune, by giving to. the public a simple, cheap, and efficient apparatus for determining the illuminating power of gas, and the pressure under which it is delivered as well as the quantity consumed.