The signal wires may be tapped at intervals all along the line, and led into small cast iron boxes placed conveniently on the telegraph poles. Conductors of all trains, furnished with keys to these boxes, can, in case of special accident, go to the nearest box, touch a key within the same, and thus set danger signals at some distance in front and rear of their trains. The telegraph keys in these boxes not only set the danger signals as described, but they also place the said signals, for the time being, entirely out of control of moving trains. THE CLOSED CIRCUIT. The new system, as described, with closed circuit, is the best ever devised for "block-signaling," since the failure of the battery through neglect or otherwise, cannot possibly be productive of disastrous results to the train, however implicitly the signals may be relied on. _From the French of Feb. 1872 [Translation]._ 88th claim. "Connecting a battery B5, and a magnet M5 with the rails _a9_, _b9_, of a section of railroad track C5 in such a manner that when said rails are joined by a metallic bridge, the electric current will be diverted from the magnet M5, but so that when said bridging device is removed from said section C5 the electric current will be free to pass through and charge the magnet M5." 93d. "A signal or signals audible or visual in combination with the battery B5 and the rails of a railroad track, the whole being arranged to actuate the signal or signals, substantially as described." ~WILLIAM ROBINSON.~ ST. PETERSBURG, Clarion County, Pa., September, 1872. It will be observed that some of the foregoing sections refer to the open circuit system, some specifically to the closed circuit system and some are applicable to either or both. The following is a photographic reproduction of a postal card issued and distributed broadcast by Mr. Robinson at the time of its date, "May, 1873." It needs no comments. ROBINSON'S WIRELESS ELECTRIC SIGNALS, THE SIMPLEST, CHEAPEST, and Only Absolutely SAFE Electric Signals in Existence, NOW IN SUCCESSFUL OPERATION ON THE BALTIMORE AND OHIO, PHILA., WILMINGTON & BALTIMORE, PHILADELPHIA AND ERIE, AND OTHER RAIL ROADS. They work as AUTOMATIC BLOCKS with tell-tale alarms, OFFICE, STATION, ROAD CROSSING and SWITCH SIGNALS, and BROKEN RAIL DETECTORS. These signals have worked uninterruptedly through last winter regardless of rain, snow, slush or sunshine. Descriptive circulars on application. MAY 1873. WM. ROBINSON, St. Petersburg, Pa. [Illustration: Fig. 3. Illustration from Robinson's Circular of "January, 1874," showing the Closed Rail Circuit, Relay and Overlapping System.]