One of tlie wpoderg óf the age is-wlmt. ia culled the "mirror telegraph." This is ii means oL eommunication in use by the United States Signal S.urVe pitrties ] thronghout the country. The teleI ..gruphing is done ly au instrument knowii as the heliotrope, which concéntrales the rays of the sun to a focus and casta thein straight ahead, similar to : mirror. By uu agreed series of long and short iiashes, the pai-ties communicale to eaeh other the temperatnre, etc. ! from point to point. Two parties fliirty-five miles apart, wcre recently oliserved commiinicating, and the flashes at that distunee were tw bright ft.s the Haches of the sun.