Though in a state of rapid improvement, the science of meteorology is acknowledged to be yet in its infancy. Before the discovery of the weight of the atmosphere by Torricelli, about the year 1630, no means of registering its variations of pressure could be known or practised. Hence we can have no very correct idea of the relative temperature of climates in the present and remote periods, unless from occasional historical remarks of the formation of ice in particular lakes, rivers, or parts of the sea, or from the capability of the earth for producing certain fruits or grain. In consequence, however, of the use of the thermometer and barometer, meteorology, as a science, has made considerable advancement. The records of phenomena, which these instruments indicate, have proved highly useful. Professor Mayer has given us a formula for determining the temperature of any situation on the globe, where observations have not been made. Dr. Hutton has presented us with an ingenious and plausible theory of rain; and Kirwan, Humboldt, and others, have advanced our knowledge of the climates of different countries. Dr. Wells has investigated the phenomena of dew, and professor Leslie has conducted profound researches on the relations of air to heat and moisture, and on the propagation of heat and cold through the atmosphere to distant regions. By the invention, also, of several curious and useful instruments, especially the hygrometer for the measurement of the dryness or dampness of the atmosphere, he has contributed very largely to the advancement of meteorological knowledge. The temperature of the atmosphere in any particular region is one of those phenomena, which, however they may fluctuate, or whatever may be their daily, monthly, or yearly variations, and however unequal and capricious these may be, will, on the average of numerous corresponding periods, be found to be dependent on certain laws tending to produce equilibrium; so that the general results are remarkably uniform. When we experience particularly cold winters, or particularly hot summers, we might suppose that the mean temperature of the years in which the former occur, would be greatly below, and that of years in which the hot summers occur, would be greatly above, the general standard. But this will seldom be found to be the case. In temperate climates of the northern hemisphere, the mean temperature of any one year, derived from the mean of the daily extremes of heat and cold, or from any particular number of daily observations, continued through the course of twelve successive months, seldom differs from the general mean temperature, as derived from the observation of a great, number of years, more than two or three degrees. The mean temperature of any single month cannot be supposed to be equally uniform; this, however, does not differ so widely from the general mean of the month as might be expected.