Page:Popular Science Monthly Volume 7.djvu/654

636 very dense, at least four times as dense as in the most thickly-peopled districts of London. Thus in the most populous district of the metropolis (Westminster) the population is 235 persons to the acre, while in the dwellings provided by the Metropolitan Association, including the large court-yards and gardens, the average is 1,140 to the acre: in one instance is is even as high as 1,620 to the acre.

Rate of Growths of Corals.—It is stated by Prof. Joseph Le Conte, in the American Journal of Science, for July, that the well-known branching or tree-coral (Madrepora cervicornis) increases in the length of its branches by growth about 3$1/2$ inches in a year. He came to this conclusion in the following manner:

At the Tortugas he found the prongs of this coral very near the surface, and all with their extremities at nearly the same level. All the prongs were dead for about the last three inches of their length, the lower limit of death appearing to be a perfectly horizontal plane. He ascertained that hundreds of acres were thus clipped, having the appearance of a clipped hedge, and he traced this result directly to a change of level of the ocean during each year. This change is about ten inches at Key West, owing to prevalent winds, the highest level being in September, the lowest in January. It is obvious that the branches of coral shoot upward with rise of water, and when near its greatest fall the new growth is destroyed. Lower down the corals are sufficiently beneath the surface to remain uninjured by the surface changes. The amount of dead coral indicates the growth, which is three inches for the growing period, or about 3$1/2$ inches for the entire year for the madrepore-stems in this region.

Methods of Physical Culture.—At a meeting of the alumni of Amherst College, Dr. Nathan Allen made some remarks upon physical culture, showing that by right it must form an essential part of a college curriculum. He instituted a comparison between boating and ball-playing on the one hand and gymnastics on the other, and said that while the former are calculated to awaken public interest on the subject of physical culture, and to improve the physical condition of great numbers, yet as a means of health they are not the best adapted for the scholar. They call into exercise chiefly certain muscles of the chest, the spine and the limbs, and when long continued produce an abnormal development of these particular muscles at the expense of other muscles. But health rather depends upon an harmonious development of the whole body. Then, too, the exercises of boating and ball-playing become at times so violent and protracted as to cause congestion in the vital organs, resulting in serious diseases and endangering life. Furthermore, these exercises can be carried on only by a few individuals, in pleasant weather and at particular seasons—circumstances which render them unsuitable to the student.

With gymnastics it is very different. These can be carried on daily and systematically by all, with little loss of time or risk of injury to person or to good morals. They can be so varied as to call into exercise every muscle of the body, and, if need be, strengthen the weak parts and repress those in excess. While they are calculated to improve the general health, by producing a well-balanced organization, they aim to bring all the physical forces of the system into the most favorable condition for study and mental improvement. They tend to bring about the greatest possible harmony of action in every part, especially between the physical and mental, so that the machinery of body and mind shall work to the best advantage.

Distribution of Ferns in the South Pacific Islands.—M. Eugène Fournier, from a study of the 259 species of ferns native to New Caledonia, whereof 86 are special to that region, and the rest common to it and other groups of islands in the Pacific and Indian Oceans, has been led to the conclusion that at one time New Caledonia and New Holland, as well as New Zealand, were united by means of Norfolk Island and other submerged islands. This hypothesis, he says, will explain the simultaneous presence, in countries with different climates at the present day, of species belonging to homogeneous groups, which the currents would not have been able to transport in