636 



THE POPULAR SCIENCE MONTHLY. 



very dense, at least four times as dense as 

 in the most thickly-peopled districts of Lon- 

 don. Thus in the most populous district 

 of the metropolis (Westminster) the popu- 

 lation 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 CoralSi 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^ 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 hori- 

 zontal plane. He ascertained that hundreds 

 of acres were thus clipped, having the ap- 

 pearance 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 prev- 

 alent winds, the highest level being in Sep- 

 tember, the lowest in January. It is obvi- 

 ous that the branches of coral shoot upward 

 with rise of water, and when near its great- 

 est 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 indi- 

 cates the growth, which is three inches for 

 the growing period, or about S^ inches for 

 the entire year for the madrepore-stems in 

 this region. 



Methods of Physical Culture. At a meet- 

 ing 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 pro- 

 duce 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 dis- 

 eases 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 systemat- 

 ically 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 ma- 

 chinery of body and mind shall work to the 

 best advantage. 



Distribation of Ferns in the Sonth Pa- 

 cific Islands. M.Eugene 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 conclii- 

 sion 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 pres- 

 ence, 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 



