On Wednesday evening, Nov. 21st., the first regular meeting of this association, under the new constitution, was held at its room, No. 24 Cooper Institute, this city Thomas B. Stillman, President, in the chair ; Benj. Garvey, Secretary. After considerable miscellaneous business had been disposed of, Mr. Gray, on behalf of the Committee on Science and New Inventions, presented the subjoined written report: Wd^-ren and Bank's Low TVater Detector.Your committee visited the place where the inventor had one upon (lxhibition, and were allowed to let the water down to the alarm mark. but no alarm was made ; after touching the lever with the point of a knife blade, the alarm sounded. In view of the fact that aii alarm, to be reliable, must always work well, or become a source of false security, we cannot report favorably thereon ; we do not c{'msider it reliable. Ashcroft's Low ]Ya(er Detector.We examined this instrument at three different places. At the Astor House, where we learned from the engineer that, in his presence and that of our vice-president, the alarm had gi,'en warning with two cocks of solid water in the boiler. At the Bible House, where the same thing occurred; and at the Cooper Union, where we found the metal had commenced to corrode after but little use-In view of these facts, your committee cannot recommend it. Hoyt's IVater Gage.We tried this instrument by letting down the water, but the whistle did not blow; not reliable. Shrimpton's High Pressure Ondenser.Mr. Shrimp-ton claims that, by the heat of the exhaust steam, he can raise the temperature of the feed water to nearly that of the water within the boiler. Your committee had only a model in their possession, and therefore could not assert the contrary ; but inasmuch as exhaust steam, without compression, can only pass 212 of tem-pcratme, we think it impossible to heat the feed water above that point. In relation to Mr. Shrimpton's other plan of passing the exhaust steam through a trough half filled with water, sufficiently long to condense all the steam, your committee say it is possible so to do, but do not believe it practicable. At this juncture, so much of the above report as related to Mr. E. H. Ashcroft's instrnment, was taken up and discussed by the several members present. Mr. Hart appeared for Messrs. Ashcroft & Co., and, for the benefit of those who had not seen the instrument, described it, and the manner of its operation. DISCUSSION. Mr. MerriamThe committee report the detector at the Astor House had operated as an alarm when there were two cocks of solid water in the boil er. Duri ng the first discussion of the merits of this instrument, it was suggested that, although water was a poor conductor of heat, yet, by its circulation, it became an excellent vehicle for the transmission or" caloric upwards, and, consequently, it was feared that the water at the top of the detector would become gradually heated until it reached 212, when the fusible plug would melt and give an alarm. Does not this report prove that deduction to be a correct one? Mr. HartIn this case, no. If the plug be not screwed up tight, or if, from any other canse, there be a leak in the instrument, the cold water will be gradually forced from it, and hot water will replace it and so melt the plug; this, doubtless, was the case at the Astor H0use, and proves, not t-hat the detector is faulty in principle, but that it was not in proper order. In rela. tion to tlie circulation of water in the tube, experiments tried by Mr. Ashcroft, with an instrument having .a glass top, have clearly demonstrated that it never occurs, or to an extent so limited, that it never in. creases the heat of the water at the plug above 150. If the detector be placed upon the top of the boiler, where there is but a little distance between it and the ceiling above, the atmosphere surrounding it is thus I'aised to a very high temperature, the plug will fuse from that cause alono. This instrument should lIever bs go p!:ioe(1, bnt oapris4 tln'oiigh the fiooi' above, leak has caused the alarm to blow when there was sufficient water in the boiler? Mr. HartI have, several; in fact. if the ball, packing or pipe leak, such a consequence would be inevitable. Mr. GrayAs an engineer, then, I cannot recommend the instrument to my associates ; for if, during the temporary absence of an employer, the alarm whistle should blow, I would be discharged, when, in reality, I may have kept my boiler well filled. The report of the committee was also upon the fusibility of the plug: we found the one at the Cooper Union corroded, and that after having been used but a few times. I dislike the idea of referring instruments back to the committee. We examined two of them, as requested by the owners, and found them both faulty. We reason, therefore, upon the fact that, in a low water detector, one case of failure in principle is sufficient to condemn it, inasmuch that one faulty instrument would do more damage than a hundred would do good. Mr. Hart, during h is remarks, alluded to the fact that the air at fii'st compressed into the ball became, by contact with the water, absorbed ; consequently, in a short time there would be no air remaining within the ball. Mr. SimpsonUpon the first trial of the detector at the Cooper Union, in the presence of Messrs. Cooper, Renwick and others, the water was let down to the alarm point, when the whistle " hung fire" for a short time, and then blew; on being asked w hy this was so, the gentleman in ch arge of the instrument replied that, in orrler to be sure the pipe was full of water, he had not tightened the plug until the air was expelled, and therefore he believed that it was owing to the absence of a pressure of compressed air, to expel the water, that it remained so long in the tube. If his reasoning was correct, and what Mr. Hart says is true, then, after an instrument has stood for some time, the water will be heW in the tube by the pressure of the steam. Mr. HartMr. Battles, the person Mr. Simpson alludes to, was wrong; he was not so well informed of the operation of the instrument then as now. The trne cause of the tard y working was, on the contrary, the presence of that air in the instrument. You sa y it was just put up, consequently, the ball was full of compressed air, which did not descend with the water; therefore, the steam had first to displace the air before it could reach the plug. Mr. KochAlloys change their fusible point upon being corroded; now, if the fusible point is constantly changing, we never can know when we are safe. Mr. HartI should be glad if you would try the fusibility of the plug .vou have ; put it in water at 212, and yon will find it to fuse in spite of the slight corrosion it may have. Mr. RhoedenSuch a trial would be very unfair; rather let it he tested with hot' water or steam upon the side that is corroded. Besides, this plug has been hut very little used, and we argue, from the corrosion already apparent, that six months would render it valueless. Mr. Hart stated that Mr. Ashcroft would forfeit $1,000 for every plug made by him that would not fuse at 212, after two years use. At this period the subject was laid over for one week. The society then adjourned. FREE ADVICE TO INVENTORS.It is the custom, at the office of this paper, to examine models or drawings and descriptions of alleged new inventions, and to give written or verbal advice as to their patentability without charge. Persons having made what they consider improvements in any branch of machinery, and contemplating securing the same by Letters Patent, are advised to send a sketch or model of it to the SCIENTIFIC AMEEICAN Office, and obtain the opinion of the publishers as to the prospects of obtaining a patent. Such advice is rendered free by the publishers of this paper, who have had fifteen years' experience in the examination of'inventions and the procuration of patents. THE BEST VIOLIN IN THE COUNTRYSO say, as we are informed, some of the most prominent musicians, referring to the instrument now in possession of Capt. John Brooks, of Bridgeport, Conn. It. is a genuine Cremona, Jlade by Nicholas Amati, and is valued r.t