THE POPULAR SCIENCE MONTHLY.
skillful cultivation. The industry thrives in the province of Kampot, where it is pursued in some twenty villages. At the village of Suam Ampil there are eighty-nine planters and more than a hundred plantations, containing 48,441 stocks. The plants are propagated from cuttings, which are made about eighteen inches long and are taken from stocks two or three years old; they are supported by stakes about ten feet high, which are solidly planted in the ground; and are fertilized at the same season every year with a special manure which is composed of eight parts of good soil and one part of pounded shrimp shells. The plants are liable to attack by a minute parasite that destroys their fruitfulness, to obviate which they are treated with a decoction of tobacco. The first crop, but an insignificant one, appears in the third year from planting. A crop of about a kilogramme per stake of two plants is gathered in the fourth year, and the increase continues for eight or ten years. Exceptional plants in good soil may return four kilogrammes per stake; but a crop of from two to two kilogrammes and a half is considered a fair average. Some plants will live fifty years, but they are seldom remunerative after forty years; and, as a rule, a plant thirty-five years old is considered of no further value. The plants bloom in May and June, and the gathering of the crop begins in February. The bunches which have turned red are picked, and the others are left for future visitations. The berries are stripped from the bunches and dried in the sun till they are black, when they are packed and made ready for sale. White or gray pepper is produced by letting the berries get a little riper, and cleansing them from their outside envelopes. In some districts the removal is assisted by soaking the berries in sea-water. One laborer can usually take care of about one thousand stakes.
Yaks, Wild and Domestic.—Immense herds of wild yaks still pasture on the steppes in the region of the Lob Nor and Thibet. Individual species have been domesticated and are as cows and oxen to the people of the country. Thick and strong cloths are made from their hair; the tufts of their tails are used in standards; their meat is juicy, and their milk is not inferior to that of our domestic cows; and they are highly valued by the Thibetans as draught and pack animals, and even for riding, on account of their hardiness, readiness, and sure-footedness. Attempts have been made to domesticate them in France, but the climate proved not suitable to them. Comparison of the skins of domestic yaks with those of wild ones shows how the animal has been modified under human influence and through changes in its medium. The hide of the domestic yak has become fine, is often silver-white, or gray varied with white; and the horns, when they have not disappeared, form a simple curve outward and upward; while in the wild yak the hide is uniformly black or very lightly shaded with brown, and the horns, which are nearly three feet long, describe an incomplete S, starting outward, then growing forward and then upward. Judging from the specimens presented to the Paris Museum by the Prince of Orleans, the wild yaks are much larger than the domestic animals, and the long hair on their flanks and legs grows lower down. Like the buffalo, these animals are dangerous to hunt, unless they are killed at the first shot.
Color Phenomena on Mars.—Prof. W. H. Pickering writes to the Journal of Astronomy and Astro-Physics concerning his observations of Mars at Arequipa, Peru: "The sudden changes of color exhibited by some of the smaller areas upon the planet Mars are sometimes almost startling. A recent view was obtained shortly before sunrise, when the snowy region about the south pole appeared of a most brilliant green, quite equaling in color the rather narrow green band situated just to the north of it. Later, as the sun came up, the color of the snow changed to a bright yellow, the rest of the disc changing in the mean time to orange. Later the seeing improved, several of the canals became visible, and the snow became as colorless as upon our surrounding mountains. The two former effects were probably due to bad seeing, the fluctuations of our own atmosphere superporing the colors of the surrounding regions upon the snow. We have laid it down as a rule never to rely greatly upon our color observations unless the snow-caps of the planet appear perfectly colorless and the canal system is well defined." A curious feature of