We have received a communication from John Watson, of Louisville, Ky., in reference to the article on page 186, referring to the charge of E. Prince, of Brooklyn, N. T., against gas companies employing meters constructed to register a greater amount of gas than that consumed by customers. Our correspondent states that there are over 3,000 gas meters in use in Louisville, made by different manufacturers in Philadelphia, New York, nnd in London, England ; that they are all carefully tested before they are used ; that they register correctly; and that gas consumers are not deceived by them. The gas works in Louisville have apparatuses for testing the quality of the gus and the correctness of the meters, and these are at the service of customers at all times. He states that a pnb-lic inspector may do very well in la. go cities, but the expense of such an office would be too great for small towns and villages. He is undoubtedly correct in this opinion. A bill has been brought into the Legislature of New York to appoint a public inspector of gas meters for this city; and perhaps it will become a law, thus creating a new office, which would be very satisfactory to the public if proper persons could be appointed for the purpose. But in a city like this, where appointments are made on political grounds, without regard to the fitness of the appointees, we question if a Board of Inspectors would be of much benefit to the gas consumer. One thing, however, the gas companies should be compelled to do, and that is, to permit every householder to oicn-the meter, if he should wish to purchase it, subject to the control of the company, or else to reduce the rent of meters to a reasonable charge. At the present rent charged by our companies for meters, they must realize at least 40 per cent per annum on their cost, which is at least 30 per cent too much. Mr. Samuel Down, who manufactures all the meters for the gas companies of New York city and Brooklyn, has called upon us since the above was in type, and contradicts every allegation made by Mr. Prince relative to the incorrectness of the gas meters made by him; and he states that he has supplied, in various sizes of meters from his manufactory, during the past ten years, the enormous number of 80,000 meters ! He also states that it will give him pleasure to see any consumer of gas at his factory at 22d street, near 10th Ave., New York, and to prove any gas meter made by him and in use, and invites all such to call. It will give him pleasure to see any scientific gentlemen who may feel an interest in the question, and to have them examine and test, to their own satisfaction, the accuracy of tho instruments used in proving the gas meters. The process is very simple, and easily explained and understood; and if those who have doubts on the subject will call, he will cheerfully give them such evidence as will satisfy them that there is no article of commerce more accurately measured than the gas which is habitually dealt out to them by the companies so unjustl' abused.