144 THE Marine REVIEW Fic. 3--Water Controt SYSTEM. Fic. 4--Section AND~PLAN oF AIR VALVE CHEST. / / First Position, April, 194 Wikinc SeELF-DUMPING BARGE. slide-valve when it is desired to dump, This rope is carried to the tug which is towing the 'barge. When the barge takes up an extreme position while dumping, as explained above, it is necessary to interconnect tanks. D> and C. This is done by opening the valve g, which may be seen in Fig. 3. The valve is operated by a rod connecting from the lever » on the slide-valve gear as shown in Fig. 4. The arrangement of the valve-oper- ating mechanism will be seen in Figs, 4 and 5. The cross-head of the slide- valve rod is fitted with a pin and roller, which work in the grooved path of a cam carried by the operating- lever spindle. One side of the cam is formed with four ratchet-teeth, which are acted on by a pawl pivoted on the operating lever, in such a way that as the lever is pulled forward through 90 degrees into the position indicated by the dotted center-line in Fig. 4, the cam will also be rotated through 90 degrees. In addition to operating the slide-valve, the grooved cam is also arranged to- control the position of the lever n, which is con- nected to valve g. The short end of the lever is formed with a_ spherical bearing surface which lies in the cam groove in such relation that the levef is swung through an arc of about 30 degrees by the variation in the radius of the groove. The arrangement will be understood from Figs. 4 and 9. -- At the commencement of the cycle of operations the apparatus will stand as shown in Fig. 4, except that stop ?