of 226 North Ninth Street, Brooklyn, New York city, which ladder is so arranged that by releasing a retain ing device, it will be autollJatically thrown out of an open window into the street. Held in bearings at the side of the window, well above the head of a person, is a bracket.in the form of a right-angled triangle. The base of this triangular hracket carries a steel loop which supports, the folded steel ladder, made in any desired length. In order to THE LADDER FOLDED ' j,ND LAUNCHED.

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... orce the loop, and to hold it in substantially hor.i zontal position, a vertical brace is employed, extendin/r upwardly behind and in contact with the hypotenuse of the triangle. The verticalmelllber of the triangular bracket, journaled in the bearings, is surrounded by a powerful coiled spring, the upper end of which is ex tended laterally to form a stop, which limits the inward motion of the bracket. A fastening device which can be released by a pull-cord, lever, or electric push-but· ton is provided for the base of the bracket. When the fastening device is released, the strong steel spring instaritly swings the bracket through a semicirde to the open window, with such speed that the momentum acquired launches the fire· ladder into the street, so that it hangs as shown in our illustration. Not the least interesting feature of this simple device is the construct, ion of the ladder. It will be ob served that side runs are employed, between which, AN IMPROVED VALVE FOR STEAM RADIATORS. An invention has been patented by Mr. Timothy S. Martin, of Butte, Mont., which provides a simple valve mechanism particularly adapted for use on radiators through which exhaust steam is passed, and designed to reduce back pressure against the engine. Fig. 1 is a central sectional elevation of the invention with parts broken away. Fig. 2 is a perspective view, also with parts broken away. The radiator is constructed with the usual upright tubes connected with upper and lower horizontal cir culating-tubes. At the end of the circulating-tubes, a valve casing is located, comprising two chambers, which can be connected with the steam-supply. A central apertured partit. ion separates the chambers. The casing has also two outer chambers and two outer apertured partitions, one between each outer chamber and tbe adjacent chamber connected with the steam supply. A central valve is arranged to open and close the aperture in the central partition; and two lateral valves are arranged to close the apertures in the outer partitions .. A cross-head connects the outer valves and, bas ' a screw-threaded aperture. Aheadconnected with the central valve has an aperture with a screw-thread of a direction opposite to that of the cross-head, the two threaded apertures being alined axially. A valve operating shaft is mounted to turn in the casing, but is held against longitudinal movement, and is provided with screw-threads of opposite directiol}s engaging the oppositely threaded apertures of the lreads. When the center valve is closed, the outer valves are opened (Fig. 1), so that the steam enters one of the circulating : 'pipes, passes through the outer cham ber and open partitions to the radiator and returns through the other circulating pipe. If the center valve be opened by turning the shaft previously mentioned, the inlets to the radiator will be closed, and steam wilf not enter the radiator. It is evident that under these conditions the steam' will not encounter a solid, closed val ve, as in the customary construction, but will pass through the valve·casing and back to the boiler, thereby obviating the back press pre usually caused by cutting off the steam at the radiator. e .•.• EXAMINATION OF THE DRINKING WATER OF BROOKLYN, NEW YORK. The advances in sanitary science in the past few years are nowhere more marked than in water examination. The splendid work done by the Massachusetts State Board of Health has been followed by the installation of laboratories in most of our American cities for the examination of the water furnished by the municipal ity. It is naturally understood that departments of water supply should be responsible for the quality, as well as the quantity, of water furnishtid. This de mands a constant knowledge of the sanit8;ry condition of the water supply, which can be attained only by frequent analyses and inspection. The water supply of Brooklyn is complicated, and JUNE 30, 1900 . peculiar conditions of a chemical and biological labora tory. In the SUPPLEMENT for the current week there is a very full paper upon the Mount Prospect labora tory, presented by Mr. Whipple before the Brooklyn Engineers' Clu b. It deals with the collection of sam ples and with the work carried on, and to this article we refer our readers who desire more extended informa tion on the subject. The laboratory occupies the upper portion of the building and is divided into three rooms. One room is known as the general laboratory, the second the bio logical laboratory, and the third the chemical labora tory. In the basement is a physical laboratory, store room, etc., and there is a sub-basement suitable for bacteriological work during hot weather. The labora-THE, MARTIN RADIATOR VALVE. tories are equipped with the latest apparatus known to science, including ice chests for the storage of cul ture media, incubators, sterilizers, balances, desicca tors, steam baths, stills for ammonia distillation, Sedg wick-Rafter filters, a combustion furnace, a Mahler bomb-calorimeter, etc. The laboratory force consists of one biologist and director, one chemist, one aSt!ist ant chemist and three assistants. The routine work consists of the regular examination of the samples of water received from all parts of the watershed and dis tribution system, i. e., from the driven wells, streams, ponds, aqueducts, reservoirs, etc. The complicated and varied character of the water supply requires the examination of an unusually large number of samples, and it is safe to say that no water supply in this coun try is examined more thoroughly and minutely than that of Brooklyn.