But it is high time now that we should come back to our little wooden house on the beach, and tell what we know of its occupants and uses. The courteous gentleman (in a blue flannel suit for "roughing it") who sits at the telegraphic wires is Sergeant G----, belonging to the Signal Service Department of the army. Instruction in this department is given at Fort Whipple, Va. One hundred officers besides Sergeant G---- are now in charge of stations, with 139 privates as assistants. The average force at Fort Whipple is 140 men. These men are, in point of fact, soldiers liable to be called into active service in the field: their duty there, however, is not fighting, but signaling and telegraphy--a duty quite as dangerous as the bearing of arms. Fresh recruits for this service are divided into those capable of receiving instruction only in field duty and those for "full service," which includes, with military signaling and telegraphy, the taking of meteoric observations, the collating and publication of such observations, and the deduction from them of correct results. Passing two examinations successfully in the latter course, the signal-service soldier is detailed for duty at a post as assistant, and after six months' satisfactory service is returned to Fort Whipple for the special instruction given to observer-sergeants. When qualified for this work he is detailed, as a vacancy occurs, for actual service. Having thus discovered how our friend the sergeant came into his post, we looked about to see what he had to do there. The brilliantly-colored flags overhead drew the eye first. These flags serve the purpose of an international language on the high seas, where no other language is practicable. Twenty thousand distinct messages can be sent by them. Rogers's system has been, adopted by the United States Navy, the Lighthouse Board, the United States Coast Survey and the principal lines of steamers. Each flag represents a number, and four flags can be hoisted at once on the staff. With the flags there is given a book containing the meaning of each number. Thus, a wrecked ship cries silently to the shore, "Send a lifeboat" by flags 3, 8, 9, or says that she is sinking by 6, 3, 2; or a vessel under full sail hails another by 8, 6, 0, or bids her "_bon voyage_" with 8, 9, 7. Owing to the difficulty of distinguishing colors in cloudy days or when the flags will not fly, other systems of signaling are used: that of cones similar to umbrellas being considered in the English service one of the most efficient, a different arrangement of cones on the staff representing the nine numerals. Men may convert themselves into cones in an emergency by raising or letting fall their arms, and two men thus give any signal necessary. As the flags, however, belong more especially to Sergeant G---- 's duty on the field of battle or to exceptional cases of storm and danger, we pass them by to examine into his daily round of duty.