Page:Popular Science Monthly Volume 10.djvu/133

Rh sugar, which goes to support the young leaves. From this time forward until the moment when the rudiments of the seeds appear, the sugar remains in the root. Hence it would appear that the carbon requisite for the formation of the stems and leaves, which during this period attain a great development, comes mostly, if not entirely, from the atmosphere. From the time when the seeds appear, the sugar in the root disappears rapidly, and when the seed is fully ripe there is no more left.

The Kauri Pine.—The kauri pine is one of the chief timber-trees of New Zealand. These trees in some instances have been found fifteen feet in diameter and one hundred and fifty feet in height. In some kauri trees the wood is prettily marked or mottled, and is in great demand for cabinetmaking. The timber is also valuable for ship-building. The kauri does not grow farther south than latitude 37° 30'. The gum which exudes from this tree is an article of commerce. Over a large area of land which has been exhausted by kauri forests in past ages, and is now barren, the gum which has exuded from the dead trees is found at a depth of from two to three feet. This gum is valuable in the manufacture of varnish. During the years 1870, 1871, and 1872, no less than 14,276 tons of the gum were exported, amounting in value to nearly half a million pounds sterling. The Maoris bring a considerable quantity to market, and the proceeds thus obtained enable them to procure the comforts of dress and living to which they have now become accustomed.

An Important Sanitary Fact.—The following interesting statement is made by Dr. Littlejohn, Medical Officer of Health for Edinburgh: "Edinburgh consists of two distinct towns, an old and a new, but with very different populations. The new town is inhabited by the better classes, and is preeminently a water-closet town; whereas the old town consists for the most part of overcrowded tenements, in which pails are used for the reception of excreta. These pails are brought to the street daily and emptied into carts provided by the authorities. Considering the low morality of the population, the bad ventilation, the overcrowding, and the retention of the filth in the living-rooms for the greater part of the day, it might naturally have been supposed that typhoid and diphtheria would be endemic in the old town. This is not the case, however, for, despite the surrounding conditions, these diseases may be said to be practically unknown. But in the new and water-closeted town the case is quite different: typhoid and diphtheria are never entirely absent, are frequently epidemic, and it has been noticed that the ravages of these diseases have been greatest in the best houses. The lesson which this teaches is, that any system of removal cannot be sanitary unless all the excremental produce of a population is so promptly and so thoroughly removed that the inhabited place, in its air and soil, shall be absolutely without fecal impurities."

Utilization of Sewage in England.—Down to the year 1874 the sewage of the English town of Coventry (population 40,000) was cast into the river Sherbourne in an undefecated state. It rendered the stream black and disgusting, and a terrible nuisance to the neighborhood, as well as a great source of danger to health, inasmuch as the sewage, at a few miles distance, found its way into the source of the water-supply of the town of Warwick. But, by the erection of sewage-works, all this has since been remedied, and the river Sherbourne has been so purified that fishes have returned to its waters. In selecting a site for the works, advantage was taken of a fall of six feet in the nature of the ground, so as to avoid the costly expedient of pumping the sewage, and to work it throughout by gravitation. A narrow strip of comparatively valueless land along the river-bank, about thirteen acres in extent, was thoroughly drained and embanked against the rising of the river during floods. The sewage is here subjected to four processes, viz.: 1. Straining by means of mechanical strainers, thus removing the solids, which form a rich manure. 2. Chemical treatment by sulphate of alumina and milk of lime, and precipitation. 3. Filtering of the effluent water by percolation through a depth of five feet of earth. 4. Drying of the precipitate or sludge in the precipitating tanks. The cost of purifying