MESSRS. EDITORS-I might write you a long letter about the new Steamboat Law which has just gone into effect, and which, ir one particular, bears pretty heavy upon oui ligh-pressure boats, viz., in the amount or leight of steam they are limited to carry J leretofore there has been no limit, and whenever a boat did not wish to be beaten, they vould hang extra weight upon the boiler ralves. But now that they cannot carry more ;han 110 lbs. standing weight, or 160 running, t is a very different affair, and I think many )f our fastest boats will fall much short of the speed they have made heretofore. I see not low they can help themselves, unless it be by throwing aside their present engines and substituting larger ones, in order to get additional piston surface to make up for the diminished pressure; but then there is a serious objection bo that, as the weight of machinery would be boo great for the ordinary depth of water in Dur Western rivers. Many engineers object to the law, but I believe it is mainly because the law objects to them. J. 0. Campbell. Louisville, Ky.