Page:Popular Science Monthly Volume 3.djvu/108

98 came in contact with the moist air over the stream. The following morning all the trees, especially the pines, were covered with a heavy-hoar-frost, but on the land-side only, not on the water-side. On examining the ice-spicules, they were found to be perfectly crystalline, with angles of from 60° to 120°, and the long needles were made up of minute crystals set one upon another, and on one side resembling a flight of stairs. The particles of water floating in the air were, of course, of the temperature of the atmosphere, and consequently below the thawing-point. So soon as they came in contact with the points of the ice-spicules, they solidified, just as very cold water will when it is touched with ice. If the particles of mist had been changed into ice while still floating in air, they would have gathered upon the spicules of the pines in the shape of irregular pulverulent conglomerates, but would not have formed crystals. The plainly crystalline form of the ice-spicules shows, beyond a doubt, that the particles of mist were fluid at 4° Fahr. From these facts it follows that the minuter the particles of a liquid body are, the further they can be brought beneath their thawing-point without freezing.

If, now, we make an application of these facts to the above phenomena of organic Nature, we find that the reason why watery humors of pupæ, eggs, leaves and shoots, do not freeze, is because the cells containing these humors are very minute: in other words, the larger the cells the more quickly will plants freeze. It is well known that the young sprouts of vines, potatoes, and other plants, very readily freeze under a light frost, as was the case on May 12th of last year. Now, these young sprouts of vines are extremely juicy, containing a great quantity of water, and consequently but little cellulose. And, although the vines of the preceding year stood a winter temperature of 2° Fahr. without freezing, the sprouts of the self-same plants were frosted at 21° Fahr. Freezing expands the water and bursts the cells, and the break-up of the texture stops the process of growth. The buds of vines are more watery than the ligneous vines themselves. Hence, too, last winter, on the night of December 7th, many buds were frozen, while the vines were unhurt. On a vine eight feet in length, one of the latest of the buds rested on a wall covered with snow, and this shot forth in the spring, though all the other buds on the vine failed. It was the coming of the frost so early in December that made it so destructive, for the vines grow ever drier, and the sap tends toward the roots, from the beginning of autumn. This process had not gone so far in December as it would have gone in the first half of January, when usually the heavy frosts set in. Those branches whose buds are destroyed by frost, afterward die of their own accord, because the sap is unemployed, and the work of the leaf has ceased. Several of the vines remained green, and flourished toward the end of April on being pruned, but afterward dried up, as their buds were without life.