Page:Popular Science Monthly Volume 36.djvu/880

860 Chirambira Bay, and the higher waters of the river Atrato, which flow into the Atlantic through Choco Bay, in the Gulf of Darien, so that they could pass from the Caribbean to the Pacific in their canoes. In carrying this passage into effect, the Arastradera, or summit level, a plain about three miles in width, formed by an interruption of the mountainous ridge, was cut across. The passage was, however, dangerous and difficult at all times, even for canoes, and the communication has now for many years been neglected and disused.

Land Tenures in China.—While the emperor theoretically owns all the land in China, the private owner has as absolute a property in it as he can have under any government. The tenures are military and common, the latter applying to far the largest proportion of the territory., It exists upon the conditions of payment of the land-tax, the supply on demand of statute labor to the authorities, and the payment of a fine on alienation. The land-tax is assessed in a fixed sum on the district magistrate, who recovers from the tenant, but is sometimes remitted in case of a great calamity. The supplying of statute labor has almost fallen into disuse. The fees are payable on the transfer of land by sale or mortgage, succession or inheritance. About half the soil is probably the property of the tenants who till it; but large tracts are also owned by "literati and gentry," who lease it to small farmers for a rental consisting of a proportion of the crops fixed according to the quality of the soil. The rents are paid as soon as the crop is harvested, and, being seldom in arrear, evictions are rare. The laws are all in favor of the tenant, who pays no taxes or rates, and takes everything, including his house. There is every possible variety of arrangement in the ownership of land. There are absolute sales and sales in which the vendor reserves the right to a share in a future rise in value; revocable and irrevocable sales; and dual ownership, in which one man owns the surface and the other the soil, and is liable for the taxes.

Refrigeration by Ammonia.—Ammonia has been very generally employed for refrigerating purposes in the United States and Germany, and to some extent elsewhere, for ten years or more. Other agents used for this purpose are methylic ether, Pictet's liquid, sulphur dioxide, and ether. Ammonia in its anhydrous condition possesses in an eminent degree the properties most desired in a refrigerant, for it boils at the low temperature of 37° Fahr., while its latent heat of vaporization is 900°. Two distinct systems are employed in the use of ammonia, differing from one another in the method of securing the rejection of heat during condensation of the vapor, while the mere evaporating or refrigerating part of the process is the same in both. In the absorption process ammonia and water are vaporized together and then fractionally condensed by cooling. The water, condensing first, is caught and run back to the generator, while the nearly anhydrous ammonia is collected separately. With this process 200,000 units of heat per hour may be eliminated by the consumption of about one hundred pounds of coal, with a temperature in the refrigerator of about 20° F. In the compression process the ammonia vapor is drawn from the refrigerator and compressed by a pump and delivered into the condenser and liquefied at the temperature of the cooling water. It is more economical than the absorption process, and is adequate to the elimination of 240,000 units per hour. The process is applied to ice-making and to the cooling of stores and rooms.

The Tahl-tan Indians of British Columbia.—An account of this people by Mr. J. C. Callbreath, included in a report of an exploration by George M. Dawson, gives their maximum height as about five feet seven and a half inches, and maximum girth of chest about thirty-seven inches. Their heads are small, and the feet and hands are generally small, as are also the wrist and ankle, especially in the women. Traders sell more No. 2 women's and No. 6 men's shoes than any other sizes. No men's hats above No. 1 are sold. Half-breeds from a white man and a Tahl-tan woman are more like the father than the mother, and three generations where the father is in every case white seem to obliterate all trace of Indian blood. The children are more cunning and clever when young than those of the white race, but grow dull as they age. Yarn is spun from the wool of