The cause of the expansion of water during its conversion into ice is not yet well ascertained, it was supposed to have been owing to the air being set at liberty in the act of congelation which was before dissolved in the water, and the many air bubbles in ice were thought to countenance this opinion. But the great force with which ice expands during its congelation, so as to burst iron bombs and coehorns, according to the experiments of Major Williams at Quebec, invalidates this idea of the cause of it, and may sometime be brought into use as a means of breaking rocks in mining, or projecting cannon-balls, or for other mechanical purposes, if the means of producing congelation should ever be discovered to be as easy as the means of producing combustion. Mr. de Mairan attributes the increase of bulk of frozen water to the different arrangement of the particles of it in crystallization, as they are constantly joined at an angle of 60 degrees; and must by this disposition he thinks occupy a greater volume than if they were parallel. He found the augmentation of the water during freezing to amount to one-fourteenth, one-eighteenth, one-nineteenth, and when the water was previously purged of air to only one-twenty-second part. He adds that a piece of ice, which was at first only one-fourteenth part specifically lighter than water, on being exposed some days to the frost became one-twelfth lighter than water. Hence he thinks ice by being exposed to greater cold still increases in volume, and to this attributes the bursting of ice in ponds and on the glaciers. See Lewis's Commerce of Arts, p. 257. and the note on Muschus in the other volume of this work. This expansion of ice well accounts for the greater mischief done by vernal frosts attended with moisture, (as by hoar-frosts,) than by the dry frosts called black frosts. Mr. Lawrence in a letter to Mr. Bradley complains that the dale-mist attended with a frost on may-day had destroyed all his tender fruits; though there was a sharper frost the night before without a mist, that did him no injury; and adds, that a garden not a stone's throw from his own on a higher situation, being above the dale-mist, had received no damage. Bradley, Vol. II. p. 232.