On the other hand, it not only gives a more extended meaning to all the statistics which partially represent the climate of a place, and to the relation of the diurnal to the general changes of weather; but it also enables new inferences to be drawn, which had hitherto been impossible from some observations, and explains why other sets of figures must always remain without any physical significance. We may notice here an attempt which has been made by one school of meteorologists to deduce all weather _à priori_ from changes in the radiative energy of the sun; that is to say, that from a knowledge of greater or less heat being emitted by the sun, they would treat the consequent alteration of weather as a direct hydrodynamical problem. Given an earth surrounded by fifty miles of damp air, and a sun at varying altitude, and of varying radiative energy, deduce from that all the diverse changes of weather. This is doubtless a very tempting ideal, for there is no doubt that the sun’s heat is the prime mover of all atmospheric circulation; but when we have explained what the nature of weather changes is, we see that there is little hope that this method will ever lead to satisfactory results. Other meteorologists, who lay less stress on the varying power of the sun, have taken up the indications of synoptic charts, and endeavored to construct a mathematical theory of cyclones and the general circulation of the atmosphere. Ferrel, Mohn, Gulberg, Sprung, and others have all started with the analysis of the motion of a free mass of air on the earth’s surface, first given by Professor Ferrel, and worked out, from that and other general principles, schemes of the nature and propagation of cyclones, and of the general distribution of pressure over the world. THE ROMANCE OF A RAINDROP --ARTHUR H. BELL Depth of rainfall is, of course, ascertained by means of a rain-gauge, which measures the amount of water precipitated from the atmosphere during certain definite periods--usually twenty-four hours. Sir Christopher Wren has the credit of constructing the first rain-gauge; but they have been made in various shapes and sizes since his time; and perhaps none of the instruments in the meteorologist’s armory is so familiar to the general public as the rain-gauge. The methods of using the instrument and the meaning of rainfall statistics are also thoroughly understood nowadays. However, behind these statistics and the methods of obtaining them, there are questions of great interest that obtrude themselves when we are watching the falling rain, and we desire to learn about the history of the raindrop--for example: Why is a raindrop round? How are raindrops formed? At what particular time does vapor become visible as mist? And what are the causes which change this mist into cloud and subsequently into rain?