few particulars connected with it, which are perhaps not generally known, and which may hereafter be serviceable as data for investigating the cause. It is well known to meteorologists that a severe frost in winter does not always commence in a uniform manner. Sometimes it begins with a gentle wind from the E. or N.E., and is at first comparatively mild in its operations, but afterwards gradually increases in intensity. Frosts of this kind are generally more lasting than others, and during such, I have not observed that any ice is generated at the bottoms of streams; though the deep and still parts of rivers are often frozen over to a considerable extent. At other times, during the continuance of the violent south-westerly gales which are so prevalent in this country in the winter months, the wind frequently shifts on a sudden from S.W. to N.W., commonly about an hour before sunset, and blows with great impetuosity in the latter direction, attended with a severe frost, and sometimes with a heavy fall of snow. The effects of this frost, in places exposed to the wind, are extremely rapid, so as to render the ground impenetrably hard in about a couple of hours from its commencement. Situations that are not so much exposed seem comparatively little affected--at least, I have repeatedly observed that a small sheltered pond in a field was nearly free from ice, while the current of a large and rapid river at no great distance was nearly choked up by it. I believe that the phenomenon under consideration seldom occurs except during such frosts as these, and the following are the principal circumstances connected with it which I am able to state from my own observation.