June 11, 1909] 



SCIENCE 



947 



to quartz monzonite. Associated with some of 

 these batholiths as marginal facies, as small 

 stock-like masses, and as dikes cutting both igne- 

 ous and sedimentary rocivs, are rocks of aplitic 

 habit characterized by the presence of lime-soda 

 feldspar usually in excess of alkali feldspar, a 

 diopsidic pyroxene, and abundant titanite. Some 

 contain scapolite; in one instance this mineral 

 formed about 20 per cent, of the rock. In this 

 rock the scapolite encloses all the other minerals 

 and interpenetrates with all but quartz and the 

 minor accessories, so that there is no doubt of its 

 primary character. Chemical analyses of two of 

 the seapolite-bearing rocks show the remarkable 

 combination of rather high SiO,, low MgO and 

 iron oxides, with high CaO and Na.O; chlorine is 

 more abundant than in most rocks. It is sur- 

 mised that these unusual rocks have been formed 

 by the solution of limestone in magmas of aplitic 

 composition containing abundant chlorine. No 

 partial stages of the assimilation have been ob- 

 served, and it probably took place at great depths. 



On the Origin of Peat: Charles A. Davis. 



Peat deposits are formed: (1) in depressions 

 below the ground water level, (2) on poorly 

 drained land areas where the ground water level 

 is near but usually below the surface. Deposits 

 on slopes in regions of high atmospheric humidity 

 and on subsiding coasts are included in (2). 



In (1) the peat is formed mainly from aquatic 

 plants, including microscopic algse, the true 

 aquatic higher plants, and a little drift material 

 from the shores. As the peat approaches the 

 water surface, amphibious plants, particularly 

 sedges, other herbs and shrubs, grow out over it 

 from the shore, and form a partly or wholly float- 

 ing mat, which, later, is invaded by terrestrial 

 plants, including sedges, grasses, ferns, shrubs, 

 sphagnum moss and trees, in the order given. 

 The time when each type appears depends on the 

 height of the surface of the mat above the average 

 water level. Peat formation may go on until the 

 basin is filled, or its surface covered. 



In (2) the plants forming the peat are mainly 

 terrestrial, but the types chiefly contributing are 

 controlled by the average height of the ground 

 water level, and climatic conditions. If the 

 ground water level rises with the peat, the entire 

 deposit may be homogeneous, and formed by the 

 same kind of plants; if it remains fixed, the bed 

 is generally thin and varies from bottom to top; 

 if the water rises periodically, the deposit is het- 

 erogeneous, with beds of the same structure re- 

 peated at intervals. 



Decomposition of vegetable matter into peat is 

 principally due to the activities of organisms, the 

 most important being aerobic, hence the top strata 

 of wet peat beds are usually most thoroughly 

 d composed. 



The Landslide at Frank, Alberta: L. D. Bukling. 



At 4:10 A.M., April 29, 1903, an amoxmt of rock 

 variously estimated at from 60,000,000 to 100,- 

 000,000 tons dropped away from the northeast 

 face of Turtle Mountain, fell through a maximum 

 vertical distance of 3,500 feet, and covered over 

 a square mile of the valley bottom to an average 

 depth of thirty to fifty feet. The slide wiped 

 out the tipple work and buildings of a coal mine 

 at the foot of the mountain, demolished eight 

 houses and a number of smaller shacks and tents, 

 destroyed about two miles of railroad track and 

 killed about seventy people. 



Turtle Mountain is an isolated mass situated 

 just south of the Canadian Pacific Railway east 

 of the Continental Divide between British Co- 

 lumbia and Alberta, and towers 3,000 feet above 

 the town of Frank, which lies at its base. The 

 upper part of the mountain is composed of massive 

 upper Paleozoic limestones which dip westward at 

 angles of 20 to 30 degrees. These limestones are 

 thrust over nearly vertical shales and sandstones 

 of Cretaceous age containing a workable coal seam 

 twelve to sixteen feet thick. The strikes of the 

 massive limestones, the thrust plane and the coal 

 beds are very nearly parallel, and for a distance 

 of three quarters of a mile (entirely across the 

 face of the mountain) and for a vertical height 

 of 300 to 400 feet, the entire coal bed had been 

 either loosened or completely withdrawn. 



The slide affected only the limestones above the 

 thrust plane. The horizontal distance between the 

 present crest of the mountain and the toe of the 

 slide is nearly two miles, the maximum vertical 

 difference 3,000 feet and the vertical distance 

 between the crest and the toe 2,525 feet. The 

 slope from the crest of the mountain to the lake 

 at its foot is 32 degrees, the first thousand feet 

 having a slope of about 65 degrees. From a 

 width of 2,000 feet at the crest the talus has 

 a width of nearly a mile at the lake, and with 

 minor variations this width is continued to the 

 hills opposite, a mile away. 



Whatever may have been the immediate cause 

 of the disaster — the period was one of frequent 

 and marked alternate freeze and thaw, and seven- 

 teen men were at work in the coal mine at the 

 time— cracks had been noticed on the back slope 



