A correspondent makes the above pertinent inquiry. We can only answer that the patentees are the most entitled to the Patent Office Reports of any class of our citizens, and a few years ago they were the first to be supplied from the press of the public printer. But, alas! the order of supplying these valuable Eeports seems to have been reversed, and it would even seem, from the vast number of letters similar in tono to the inquiry at the head of this article, that many of the patentees are neglected entirely in this respect. The Patent Office is about the only self-supporting department under our government. The inventors pay into the Treasury every year several thousand dollars more than it costs to pay the expenses of the Patent Office; and notwitlistau Jing Congressorders to be printed every year a great many thousand copies of the mechanical reports (13,500 of which were especially appropriated for Patent Office purposes, in the year 185S), yet there seems to have been such a scarcity that the patentees of last year have not been able to procure a copy. This should not be the case: no class of people prize them as the inventors and patentees ; none are so much entitled to them ; and we hope Congress will not only order enough to be furnished to the Patent Office to supply every patentee and assignee of a patent with a copy for the year I860, but that it will also instruct the Commissioner to see that they are distributed according to the intention of the statute. The Patent Offico should have the distribution of at least twenty thousand copies per annum. The Commissioner has in his department the names of persons most likely to be benefited by them, and should have the majority of the annual supply to distribute, instead of the members of the House and Senate being surfeited with so many copies as hardly to know what to do with them. ?|? m ASHCROFT's Low WATER DETECTOR.—On another page, we publish a letter from Mr. Ashcroft, in defence of his “Low Water Detector,” in answer to statements on this subject contained in our report of the proceedings of the American Engineers' Association, published in No. 24. In support of his assertions, Mr. Ashcroft ha3 shown to us a great number ef certificates from parties who have had his detector in use for several years. These certificates will be found in the advertising columns oi our next issue.