1442. Pickering, W. S., and Grove, H. Jan. 20. Purifiers.-In centre valves for gas purifiers, more particularly such as are described in Specification No. 7087, A.D. 1902, separate controlling-valves for the inlet and outlet of each compartment of the purifier are dispensed with, the course of the gases being altered, as required, by hydraulic means. In one form of valve, Figs. 1 and 2, a rectangular casing a forms the main inlet chamber, and a diagonal tubular casing c within it forms the main outlet chamber. Combined inlet chambers e', e<2>, e<3>, and outlet chambers d, d<1>, d<3>, are provided on the sides of the casing a, and communicate with the main inlet and outlet by apertures y. Each inlet and outlet chamber has a vertical partition x not quite reaching the bottom, and adjacent chambers are connected by a chamber containing a partition j<1> which does not reach to the bottom. Apertures w communicate with the inlet and outlet chambers. When water is supplied to adjacent inlet and outlet chambers and rises above the lower edge of the partition x, communication with the main inlet and outlet is cut off and the gas passes from the outlet d of one compartment of the purifier through the hood to the inlet e' of the next compartment. In order to cut out one compartment, two connecting-hoods are flooded and also the inlet and outlet chambers of the compartment to be cut out. The inlet chamber of the compartment to be worked first and the outlet of that to be worked last are emptied. In a modification, the connecting-chambers are placed between the inlet and outlet chambers on each side of the casing. Fig. 6 shows a form of valve suitable for purifiers in line, two valves being used for four purifiers. Two sets of valves are employed, each having a common inlet chamber b and outlet chamber c. Pipes connect the outlet of the second purifier with the inlet of the third, and the outlet of the fourth with the inlet of the first. The main inlet b and outlet c of one set of valves are completely closed. The dotted lines s<1>, s<11> indicate the outlets from the purifiers and s<2>, s<22> the inlets, the pipes connecting the purifiers entering apertures u<1>, v<1>. Inlets and outlets b<1>, c<1> are used when the pipes are connected to the valve by an elbow, and alternative inlets b<11>, c<11> when the pipes are connected to a separate fitting. When two purifiers only are used, both ends of the casing are formed like the right hand end of the modification shown in Fig. 6. A sectional elevation of a valve for two purifiers on the ground is shown in Fig. 9. The casing a attached to the side of the purifiers, is divided into alternate inlet chambers e and outlet chambers d, supplied by a main inlet pipe b and outlet pipe c. The two middle chambers d, e communicate by an aperture t' in the partition t, and the end chambers d', e communicate with a conduit r, from which depend hoods e', d<1>, into which project inlet pipes e<2> and outlet pipes d<2>. The hoods may be closed by a water seal, as required, an additional seal being provided by suitable partitions. The inlet and outlet chambers are furnished with apertures e<3>, d<3>, and partitions t<4> are provided for flooding the central chambers d, e. Water or other fluid may be supplied to the inlet, outlet, and connecting chambers of these valves by a controlling cock operated by one handle.