The use of the aeroplane for making meteorological observations is still quite limited, but will inevitably increase. One other device gives promise of yielding valuable aerological information, on account of its ability to rise to extraordinary altitudes. This is a special form of rocket, recently invented by Prof. R. H. Goddard, which is propelled by several successive discharges of an explosive in the course of its upward flight, and with which the inventor thinks it will be possible to explore the whole vertical extent of the atmosphere. Meteorological apparatus for use with the Goddard rocket has been planned by Mr. S. P. Fergusson of the Weather Bureau. The atmosphere presses down upon the earth with a weight that, at sea level, amounts to about 14.7 pounds to the square inch, on an average. This pressure is, at any point, exerted equally in all directions; it acts, for example, on the whole surface of the human body, and this means that a man of average size lives under a burden of some seventeen tons of air. He is not incommoded because the pressure from without is balanced by that of the air that permeates his body. The pressure of the atmosphere decreases upward at nearly the same rate as its density. Thus on mountains and plateaus it is considerably less than in lowlands. At no place is the pressure invariable, nor is there a constant relation between pressure and altitude, but, knowing approximately the average atmospheric pressure over the earth’s surface, and knowing also the area of the latter, we can compute in round numbers the total weight of the atmosphere--about 5,000,000,000,000,000 tons. This is about 1/1,200,000 of the entire weight of the earth. CHAPTER II THE RESOURCES OF THE ATMOSPHERE In the economic stress of our times much is heard about “natural resources.” This phrase suggests to most people’s minds the store of minerals, fuels, and oil locked up in the ground; the waters available for drinking, washing, irrigation, power production, and navigation; the forests and other natural growths of useful vegetation; and the soil in which we raise our crops. A moment’s reflection, however, will show that this is a one-sided enumeration. The resources of the _atmosphere_ are as essential to humanity as those of the land and the waters, if not more so.