506 AGRICULTURAL REPORT.

bright days the snow next the slate roof of a house is seen to melt, while the upper surface remains unaffected.

There is a singular phenomenon observed during the spring of the

vear in damp, sandy places, which has attracted much attention, namely, the ice-columns which spring from the earth during cold nights, ele- vating small gravel-stones on their tops, and raising, as it were, above its usual level the general surface of the ground. These crystals have been carefully studied by Professor John Le Conte, and appear to be due to the law we have before mentioned of the axis of crystallization being always at right angles to the surface of cooling, as well as to the attraction of the water for itself, and the consequent excluding effect of all extraneous bodies. The water of which these crystals are formed is drawn up from below by capillarity; is frozen as it comes up to the surface in vertical prismatic crystals; a new portion is drawn between the bases of the crystals first formed and the ground, which is also frozen; and so on the process is continued until stopped by the failure of moisture, or the increase of the temperature due to the advancing heat of the day.

The next subject in order, of which we intended to treat, was that of the vapor of water in the atmosphere; but this is of so important a character in its connection with all the phenomena of the fitful changes of the weather, and the peculiarity of climate, and agricul- tural products of a country, that justice cannot be done to it within the limits assigned to meteorology in this Report, and therefore we shall defer it until next year.

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