Page:Popular Science Monthly Volume 46.djvu/733

Rh Bilbao, in Spain, nine lines run from the station at the foot of the mountain to the mines at different levels along the summit, and carry on an average twenty-three hundred tons of ore a day, none of which touches the level of the ground through its journey of five miles. It is calculated that one hundred thousand tons of ore can be carried on each of these cables before it becomes unfit for service. In crossing wide ravines or rivers, where one bank is lower than another, the gravity system is employed, the descending load being used to haul up the ascending car. In the Italian Alps a span of fifteen hundred yards is crossed without a support, and the method is soon to be applied to distances of two thousand yards.

Effects of Freezing on Plants.—The study of the effects of freezing upon plants has made less advance than that upon the best temperature to promote their growth. Some observations oil the subject have been published by Signor Sebastiano Cavallero in Italian journals. All plants, aside from a few tropical species, resist temperatures ranging from the freezing point to —110º F. Beyond these extremes their resistance varies with the species. It is well known, moreover, that woody plants and many herbaceous plants freeze and thaw without being visibly injured. Forests of larches, birches, and pines grow in Siberia as high as the seventy-second degree of latitude, where the temperature often falls below 50 F. Several kinds of pines, willows, junipers, and alders grow along the Mackenzie River in latitude 69º. Mr. C. Gibbs, of Abbottsford, found in 1882 that the apple crop of twelve Russian villages, on the western bank of the Volga and south of Kazan, was valued at fifty thousand dollars a year. The fruits are sold in the markets of Nijni-Novgorod and Kazan. The region is subject to temperatures, as was experienced in 1887, of —40º. So apples grow well in the northern United States, where such temperatures are not unusual. The greatest resistance to cold is offered by seeds. Next in power of endurance are the cryptogams—mosses, algæ, and fungi. Except the hardy trees and shrubs of the temperate and frigid zones, and the hardy perennial herbs, most of the phanerogams perish between the freezing point and —20º. The most obvious effects of freezing upon plants are noticed in herbs and bulbs, which are stiffened and assume a shining appearance, often oleaginous and transparent. The effects of frost on trees are not visible unless the temperature descends to near zero, when they are often cracked to the center. Internally the sap is congealed in the tissues. Until recently the death of the plant was attributed to the frosts dilating the cells and distending the tissues. During the winters of 1887-'88 and 1888-'89 Signer Cavallero found, with a microscope magnifying three hundred times, that the tissues of a frozen vine were not torn and that the cells were not frozen. The crystals of ice, on the other hand, were formed only in the intercellular spaces. These facts do not afford indications of the vital condition of the plants, for they are observed in those that resist the cold as well as in those that succumb to it. The chemical modifications are of much greater importance, for they determine or attend the death of the frozen plant. Signor Cavallero's data agree with those of MM. Sachs and Jumelle, and point to the thawing as the principal factor of the death, for frozen plants may be made to live by taking precautions to thaw them slowly. In fact, while the plant is thawing rapidly, the water leaves most of the tissues before it is reabsorbed by them; and the abnormal concentration of the tissues provokes death. But when the thawing process is slow, most of the water returns to the cells and restores the equilibrium which primarily existed in them.

Sounds made by Ants.—That ants are capable of producing sounds intelligible to their fellows and even audible to our ears seems to be proved by the experiments of Sir John Lubbock, Landois, Robert Wroughton of Bombay, C. Janet, Forel, E. Warsmann, and others. It also seems to be determined that the sounds are produced by the rubbing together of superficial portions of the body. A simple yet ingenious contrivance is described for enabling an observer to hear and study these sounds. A glass tunnel is set, small end down, in the middle of a square of window glass of five or six inches side, fitting closely enough to prevent the insects crawling out under it. A bunch of ants about as