Page:Popular Science Monthly Volume 8.djvu/519

Rh Maturity of Timber-Trees.—A paper in the "Transactions of the Scottish Arboricultural Society" contains the following information with regard to the time required for various kinds of timber-trees to reach maturity: "The oak can never be cut down so profitably when small as when well matured, and having plenty of heart-wood. The timber is seldom of much value until it has reached the age of 100 years. Ash can be cut down more profitably in its young state than other hard-wood trees. When clean grown, and from thirty to forty years of age, it is in great demand for handle-wood and for agricultural implements. Beech is of very little value in its young state, and is seldom cut till well grown. Birch can be cut down profitably at about forty years old. Horse-chestnut, when grown on good soil, and in a sheltered position, can be profitably cut down when it attains large dimensions. Elms (Scotch and English) should never be cut until they are from eighty to one hundred years old. Poplars can generally be profitably sold when about fifty years old. Sycamore, growing in good soil, may be profitably cut down when about one hundred years old."

Source of the Nitrogen used by Plants.—The average life of an apple-tree in Normandy is estimated by M. Isidore Pierre at fifty years, and its nitrogen product (in leaves, fruit, wood, and roots) at 26 kilogrammes (about 60 pounds). This amount of nitrogen corresponds to 5,200 kilogrammes of farm manure, or 100 kilogrammes per year. But the tree is far from receiving any such amount; according to the author, the most liberal cultivator does not supply more nitrogen than is found in the seeds. The question then arises. Whence comes the remainder of this nitrogen? M. Thenard, in a communication to the Paris Academy of Sciences, denies that it comes directly from the soil, or from the manure, and holds that it is derived from the air through the soil. In confirmation of this, he cites the grape-vines of Clos-Vougeot, the youngest of which were planted in 1234, and which annually receive only one kilogramme of manure. The amount of nitrogen contained in this quantity of manure is inconsiderable, as compared with what is contained in the grapes, the leaves, and the wood.

Cranial Measurements.—Two noteworthy results of the comparative measurements of the crania belonging to historic and prehistoric times were dwelt upon by Prof. Rolleston, in his presidential address to the Section of Anthropology, at the last meeting of the British Association. It might be assumed that skulls from the earliest sepulchres would present the smallest capacity, and that the size of the brain-case has since increased with the intellectual development of our race. But this assumption is curiously contradicted by the facts. Indeed, the cubic contents of many skulls from the oldest known interments considerably exceed the capacity of modern European skulls of average build. Surprise at such a result may, however, be tempered by the reflection that the skulls which we have obtained from the earliest tumuli are probably those of the chiefs of their tribes, who may have been selected by virtue of their great energy. Nor should it be forgotten that in savage communities the chiefs come in for a larger share of food, and are, consequently, men of well-developed frames, and of more portly presence than their fellows. As to the poorer specimens of humanity in those days we probably know nothing, as they were denied burial in the tumuli, and have left their remains we know not where. Another curious fact is, that the female skulls from the earliest sepultures do not differ in capacity from the contemporary male skulls to the same degree as the crania of the two sexes differ at the present day. But it must be borne in mind that in those early times there was a greater struggle for existence, and that the division of labor was not carried out to a large extent, so that the tendency to a differentiation of the crania was less marked than in modern times.

An Indian Mill.—On the farm of Mr. Hollis Smith, near Marengo, Calhoun County, Michigan, there exists an interesting monument of aboriginal life, known in the locality as "The Indian Mill." As described in a letter to us by Mr. W. H. Payne, of