It may here be premised that ice of this description is seldom seen adhering to anything beside rock, stone, or gravel, and that it is more abundantly produced in proportion to the greater magnitude and number of the stones composing the bed of the river, combined (as will be further noticed) with the velocity of the current. I have been informed by a friend that he has occasionally seen it attached to solid wooden piles at a considerable depth below the surface of the water, but I never saw or heard of any on earth, mud, or clay. It is not easy to ascertain the precise time at which the process begins to take place. It appears, however, almost invariably to commence during the first night of the frost, and probably within a few hours after sunset. On the ensuing morning the first thing which strikes an observer is an immense quantity of detached plates of ice floating down the stream. Mr. Knight naturally enough supposed these to have been formed at the surface by the influence of the freezing atmosphere, and afterwards absorbed by the current; but I think that a minute inspection would have led him to form a different conclusion-- viz., that they are first formed in the bed of the river, and afterwards rise to the surface. It is true that none are to be seen in situations where there is no sensible current, and that they abound most in rough and rapid places; but on closely examining any stream of moderate velocity, yet smooth, equable, and free from all appearance of eddy or rippling, a great number of these plates of ice will be found adhering to the rock, stone, or gravel at the bottom. If they are watched with attention, they will be observed to rapidly increase in bulk, till at last, on account of their inferior specific gravity, aided, perhaps, by the action of the current, they detach themselves from the substances to which they first adhered, and rise to the surface of the water. The form of these pieces of ice is very irregular, depending in a great measure on the size and shape of the stones or other substances to which they were originally attached. Most of them seem to be of an oblong or circular figure; they are generally convex on the upper surface, and have a number of laminae and spiculae shooting from them in various directions, especially from their circumference. Sometimes when those floating pieces or plates meet with any obstruction in the channel of the river, they accumulate in such quantities as to cover the surface of the water, and become frozen together in one large sheet, but this kind of ice may be always readily distinguished from that produced in the usual way by the action of the cold air on the surface, which is smooth, transparent, and of an uniform texture; on the contrary, one of these conglomerated fields or sheets is opaque, uneven, full of asperities, and the form of each separate plate composing it may be distinctly traced. In this situation, they