farms, were thrown a quarter of a mile from the ordinary height of the river. In some instances, farms were ruined by the mould being swept from them by the cakes of ice, or by depositions of sand; while others were enriched by large depositions of mud. The damage, upon the whole, done to the state of Pennsylvania by this fresh, was very great. In most places it happened in the day time, or the consequences must have been fatal to many thousands." "I know of but one use that can be derived from recording the history of this inundation. In case of similar obstructions of rivers, from the causes such as have been described, the terrible effects of their being set in motion by means of a general thaw may in part be obviated, by removing such things out of the course of the water and ice as are within our power; particularly cattle, hay, grain, fences, and farming utensils of all kinds." The air, when dry in Pennsylvania, has a peculiar elasticity, which renders the heat and cold less insupportable than the same degrees of both are in moister countries. It is in those cases only when summer showers are not succeeded by north-west winds, that the heat of the air becomes oppressive and distressing, from being combined with moisture. From tradition, as well as living observation, it is evident, that the waters in many of the creeks in Pennsylvania have diminished considerably within the last fifty years. Hence many mills, erected upon large and deep streams of water, now stand idle in dry weather; and many creeks, once navigable in large boats, are now impassable even in canoes. This diminution of the waters has been ascribed to the application of a part of them to the purpose of making meadows. The mean elevation of the barometer in Philadelphia, is about 30 inches. The variations in the barometer are very inconsiderable in the greatest changes of the weather, which occur in the city of Philadelphia. During the violent and destructive storm which blew from the south-west on the 11th of November, 1788, it suddenly fell from 30 to 29-3/10. Mr. Rittenhouse informs me, that long and faithful observations have satisfied him, that the alterations in the height of the mercury in the barometer do not _precede_ but always _succeed_ changes in the weather. It falls with the south and south-west, and rises with the north and north-west winds.