Shortly after the close of the exhibition of the American Institute, in the fall of 1867, we recommended that society to . establish an inventor's exchange, or perpetual fair, and subsequently sketched a plan of operation. Nothing came of it, i and we had begun to despair of ever seeing any such project started. Inventors and agents have for years exhibited their models, 1 machines, and specimens in the receiving rooms or offices of hotels, where they were temporarily stopping, or carried then about, when portable, from pillar to post, having no centra j and convenient place for the exhibition of their patented im provements. The inventor, proprietor, or agent showed hii device and explained its operation at his hotel only on suffer j ence, and one hotel near our office that has heretofore beei I noted as a headquarters for this class of visitors hasperempto : I rily forbidden the further use of its rooms for these purposes j This is not to be wondered at, as the annoyance was greai I and theprofit little, if anything. The pnly recourse of the in ventor or manufacturer was, therefore, the establishment of a New York agency by constituting some dealer in articles similar to that he manufactured a partner, in a certain sense, or a sharer in the profits. But the inconvenience and annoyance was felt more by the purchaser. If a stranger in the city, his labors and time in traveling from one point to another were very considerable; "but if he did not expend both, he had little opportunity to compare articles intended for the same purpose, but built by different makers on different plans. Or if he did procure opportunities to see different machines, by visiting as many places as there were machines, he could not compare the two except as he remembered the points of those he had already examined ; there was no opportunity to examine them side by side. The anxiety on the part of the resident agent to make a sale (an anxiety entirely proper), also militated against the chances of the purchaser securing either the best article or the one he really wanted. The advantages of the particular machine he was then examining were rendered so apparent by the eloquence of the salesman, and the difficulty of detecting the fault, or faults, in the machine, without close and immediate comparison with another, was so great that it is not surprising he frequently felt, after trying his new ae-quisition, that he had not been fairly treated. This state of things was also inj urious to the inventor or manufacturer. Most members of these classes desire, and invite comparison and competition ; each feeling assured that j even if in some one or two respects another's device may be better, his, on the whole is to be preferred for superior advantages. Such competition is healthy and no conscientious manufacturer objects to it, but, on the contrary, courts it. Then, if the customer is not satisfied with the article first shown, and goes to visit some other repository, he will frequently purchase what he is still less satisfied with rather than go back and acknowledge his error. Some centrally located, fairly conducted establishment, where the inventor, the patentee, the manufacturer, and the discoverer could exhibit, side by side, their products, seemed to be demanded by the interests of each and also of the purchaser. For these reasons we have repeatedly advocated the establishment of a central burean for inventors located in New York city, the commercial metropolis of tlie country. i Such an establishment we visited a few days ago. It is 1 called the " Whitlock Exposition," from the name of its pro- - jector. It is located at Nos. 35 and 37 Park Place, west of 9 Broadway and near the City Hall Park. The building is five - stories above the street and two below, the different floors de-i voted to different classes of articles, from roots, plants, and - seeds to sewing machines and works of art. One of the floors, i. a hall of 50 by 80 feet, is devoted to trials of velocipedes. Of-fc j fices for permanent occupancy are let to permanent agents or - proprietors, while temporary exhibitors have their letters directed to the establishment,and are furnished with stationery and desks with which to conduct their correspondence. Steam power is furnished for such exhibitors as require it, and each exhibitor is entitled to an advertisement in two periodicals, conducted by the company, issued monthly and semi-monthly. The exhibitors are charged a very moderate price for the room and power occupied and used, and permanent exhibitors a very low rent for their offices. If the company make sales ! (which they do without drawing invidious comparisons be tween competing articles of the same class), they expect the usual commission. The establishment is a perpetual exhibit bition, free to all who choose to visit it. Already it has become one of the features of the metropolis. Duty to the great body of inventors, as also to the enterprising projector, impels us to this notice of the new exposition which deserves to be known. It supplies a want long felt, and its success is already assured. ------------------- 4g9 ------------------- A monster Rope A new rope, made by the Universe Works, at Birmingham, England, is of such extraordinary dimensions as to merit special notice. The rope, which is intended for shipment abroad, is 11,000 yards long, measures, 5J inches in circumference, and weighs over 60 tuns. These figures are enough to take one's breath away; but when we come to see how the monster is built up, there is cause for still greater surprise. The rope (made of Messrs. Webster and Horsfall's patent charcoal wire, laid round a hemp center) consists of six strands, with ten wires in each strand; each wire measures 12,160 yards ; so that the entire length of the wire reaches the enormous total of 726,000 yards, or 412* miles. To this has to be added the length of yarn used for the center namely, twenty-seven threads, made from Petersburgh hemp, each thread measuring 15,000 yards, and giving a total length of 405,000 yards, or about 230 miles. Adding together the wire and yarn, we have a grand total of 1,131,000 yards, or 635 miles of material all going to make up a monster wire and hemp rope a little under six miles long. Such a rope certainly has never yet been made ; and we doubt whether, excepting in Birmingham, such a one could be made. As it lies in vast coils in Messrs. Wright's machine room, it looks like a miniature Atlantic cable, multiplied by five times the cable thickness. Of course such a rope will bear an enormous strain, and its capacity in this respect is increased by the perfection of the machinery employed in the manufacture, giving the strands an exactly uniform " lay," and imparting the regularity and the precise angle of " twist," which experience proves to possess the greatest resisting and holding strength. It is said that an ingenious Frenchman, in Philadelphia, skins frogs by drawing out all their interior parts through the mouth, and then stuffs and mounts them in a variety of curious attitudes, as billiard players, velocipedists, dentists, barbers, etc. Morgan's Trade Journal for April publishes the whole of an original article on " Tobacco Pipes," written expressly for the Scientific American and credits it, unduly, to the To baeco Trade Review.