The Army Signal Corps

Correspondence of te Philadelphia Press. One of the most important and at the same time the most modest branches ot the public service in this army ia the signa] oorpa. It is an independent body, under the special and immediute control of the Commander-in-Chief, and is made up of details oí oflicers and men from each brigade of Ihe army. - It constructs and works the telegiaph Unes, accomplishes all reconnoissances, and is eonstantly on the alert lor tho transmisión of telligence to and from general and división - All over the extensivo field of work ap pointed to General McClellan, signul offieers are iound, each one closely watching for every movemont ol the enemy. There are two system-; of signalling used, by telegraph and by tlag, The telegraph is used in permanent linea, as between White House and headqaarters, or headquarters and the división quarters of Generáis, whose ground bas been efïectnally gained from the enetny. Uncertain unes, which, though baviog a prospect oi permaneney, are nevertheless at any moment liable to be removed, are run by the patented insulated wire, wbioh has so often astonished our troops, who invariably take it tor some vile seoes8on invention. This is a small wire, insulated with gutta percha and covered with twisted cotton, the whole making aflexible cord, about oue-fourth of an inch in diameter. This is carried on a reel, very rnuch üke a two wheeled Philadelphia hose curriago. A line five miles ia length can be put in' working order in two hours. Tbe reel is run along tbe fields and roads, the attendants iastening the cord to trees, or bushes, at points wbere troops wight accideutally d8turb it. Where a tield is crossed, it is left lying on the ground, aud is found to suñer no harm from the contact. Beardsley's portable magnetoeloctric instruments are used for the transmi&sion of signa's. These are light boxes, about the size of a knapstick, and are portable. Indeed, the whole tolegraph system of the anny of the Potomac is of an itinerant churactor, and the bottlod lightning runa about on horseback as rapidly as tho operator who controls it. The telegraph system is similar to the alphabetic dial píate of the Philadelphia fire alurm telegraph. Flagsignalling, however, is the form most generally used ; and is the most dangerous. Euch officer is provided with three square Hags - a white one witli a red centre, a red one with a white ceutre, and a black one with a white centre. These colors have nothiog to do with the signal code, however - the different ñngt being employed for different kiods ol weather, and dif ferent back grounds, that one being iised which will be most eonspicuous at the greatest distanc. These flags Lransmit signáis by swings, and at night a torch is substituted lor them. The manner ol their use can best be shown by an illustration. Suppose part of the army makes an advance of several miles nto the enemy's lines, a detail from the sigoal corps alwaya accompanies it. When it leavea the permanent telegraph station, an officer with bis flag 13 stationed tbere; at the first turn of the road taken, another is placed, and bo on at every point where bands in the road, or trees, or hills, or other obstructions interveue and prevent a direct view ol the last flag. - Everv observatioo made, if it bo thought necessary, is reudily signaled to the permanent station. The coinmanding officer tells the flagman with him tbe message to bo sent, and he gives his flag ihe swings which correspond to it. The next in the chain observes and repeate, and so the message goea, with lightning velocity, back to headquarters. In battle, the signal corps is of the utmost advantago. The General commanding the forces engaged places himself on a convenient spot with hia flagman. High billa in the vioinhy, out. of daager, but excellent for viewing the enemy's movemunts, are selected and tíagmen placed upon them. Everything done by the enemy is indicated. Smoke may hide an approaching column from these on whoui it is quickly marching. Some of tho signal officers, perched like hawks about the fiald, are sure to observe the eneniy, and the nest instant the goneral koowa it.'and has warned his subordinutes of the threatened danger. Baiteries tlirowing shot and shell at an enemy concealed by interveoing hills er woods, have all their movementa regulated by siguak. Miles to the right or lef't, but in position where the enemy can Ir: seen, stands the signal man witn tiold glaás and telescope. One of the guns is üred but the shell flies wide of its mark. " Little to the right" is signaled. Tbe next shot is nearer, tliough inefl'eutivo; the iing swings for " a little to the left." The third falls short. " 'f wo hundred yards fartber," speeds over the luie. The fourth strikes, and " a good s iot" informs the artillerymen that several more of the sanie sort will teach the rebels a lesson. Signal duty, from the exposure of fV,-vaa anoaorpA and their consüicious flags, which are ao many targets for the enemy's shot, is by far the most dangerous in the wbolu service. The bravest and coolest men are recjuired to perform its duties. Sharp eyesight, kaowledge of diaiauces, aod judgment are equally neeesáary to make a good signal oflicer. The code employed is, oí' course, known ouly to those in the secret. Since the beginning of the war, it has been changed once, an alteration being reudered neeessary irom the desertion of an offiuer, who communicated the lormer code to the ene my. Now, however - the cause of the rebels having becotne so desperate - but little danger of the revelation oí the secret is aoticipated. The importanee of the signal service muy be conceived by any one who knows the great distances oí opposing columns, aud ihe wide sproad oí un attacking army. A commanding general can be in but one place, acd it is absolutely necessary that he ehould have the latest information of the conditioa of every part of bis command. Every battle yet iought by this arroy bas been regulated by signáis. Tno advaDce, the retreat, tbe attack - all are doae by tbe command of a small flag, which receives its impulse from a rniin who may be sitting in his tent a dozen miles off, enjoying a fine cigar. Every discovery of the enomy'a intentions, as shown by their conduct on tha ield of battle, is made by Major Myer's efficiënt corps. These men ure among the most ueeiul in the army, yet thev never pull a triggur and seldum draw a Bword. ïhey toil on at thdir dangeroua task during all hours and tbrough all weathers. Thoy seldom are ineotioned by newspaper men, and this brief description of their duties and usefulnesa may perlmpa bring hoina to tbo country the meiit of a Gorps oí the army tvhose claims to distinclion havo heretofore been overborne by the more brilliant achievement of well conteated fiulds.