Every one who reads the daily paper is familiar with the "Weather Record," issued from the "War Department, office of the Chief Signal Officer," at Washington. These reports give, first, a general statement of what the weather has been, for the past twenty-four hours, all over the country, from Maine to California, and from the Lakes to the South Atlantic States; and then the "Probabilities," or "Indications," for the next twenty-four hours, over this same broad territory. The annual reports of the Chief Signal Officer show that in only comparatively few instances do these daily predictions fail of fulfillment. The reason these prophecies are so true is a simple and yet a wonderful one. The weather itself tells the observer what it is going to do, some time in advance, and the telegraph sends the news all over the country, from the central signal office at Washington. We shall see, presently, how the weather interprets itself to "Old Probabilities." Although it has proved such a fruitful subject of discourse in all ages, yet I am afraid many people who pass remarks upon it do not really think what the weather is made of. Let us examine its different elements. The atmosphere has weight, just as water or any other fluid, although it seems to be perfectly bodiless. We must comprehend that the transparent, invisible air is pressing inward toward the center of the earth. This pressure varies according to the state of the weather, and the changes are indicated by an instrument called a barometer. Generally speaking, the falling of the mercury in the tube of the barometer indicates rain, and its rise heralds clear weather. Sometimes the rise is followed by cold winds, frost and ice. What these changes really indicate, however, can be determined only by comparing the barometric changes, at certain hours, in a number of places very far apart. This is done by the Signal Service. Observations are made at about one hundred and forty stations, in different portions of the country, at given hours, and the results are telegraphed at once to Washington, where our faithful "weather clerk" receives them, reasoning out from them the "probabilities" which he publishes three times in every twenty-four hours. But the atmosphere varies not only in weight, but also in temperature. The thermometer tells us of such changes. Besides this, the air contains a great amount of moisture, and it shows as much variation in this characteristic as in the others. For the purpose of making known the changes in the moisture of the atmosphere, an instrument has been invented called a "wet-bulb" thermometer. We are thus enabled to ascertain the weight or pressure, the temperature, and the wetness of the air, and now it only remains for us to measure the force, and point out the direction, of the wind. This is done by the familiar weather-vane and the anemometer. The vane shows the direction, and the anemometer is an instrument which indicates the velocity of the wind.