March, 1915. 



KNOWLEDGE. 



81 



the plane of the orbit of the disturbing star. . . . The spiral 

 feature relates to the streams of knots and haze, not to the 

 individual paths of each separate constituent, which are 

 held to be elliptical. The inner parts must revolve much 

 quicker than the outer ones, so the spiral streams wrap up 

 till they merge into a disc." 



From the relatively small amount of matter that left our 

 Sun the approach of the other star is supposed to have been 

 a distant one. The close approach of two large stars would 

 cause most of their- mass to be dissipated into enormous 

 spirals, only a small fraction being left to form the nucleus. 



Returning to our own system, the expelled matter is 

 taken to have been mainly gaseous. There is supposed to 

 have been a recurrence of explosions separated by the Sun's 

 natural pulsation period : this would produce definite 

 knots in the spiral streams, these forming the nucleus of the 

 future planets. The subsequent stages are common to 

 many sj-stems of cosmogony. It is shown liow a direct 

 rotation of the planets will result : " the velocity of a body in 

 an inner elliptical orbit is on the average higher than in an 

 outer one, but at the points where the inner one cuts the outer, 

 and where alone the bodies can come together, the velocity 

 in the outer is higher than that in the inner." This seems 

 to be a sound solution of a long-standing difficulty, which 

 others had tried to evade by the hypothesis of tidal inversion. 

 According to this, the rotation was initially retrograde, but 

 solar tides turned the planet over, reversing its tides. For 

 a time it seemed that the retrograde motion of the outer 

 satellites of Jupiter and Saturn supported this view. But 

 it has now been shown that retrograde orbits are far more 

 stable than direct ones at great distances from the primary, 

 and this is probably a sufficient reason for the behaviour 

 of these satellites. 



The stages of the Earth's subsequent history are traced 

 as follows : — 



(1) One of the knots in the spiral formed a nucleus, 



which slowly grew by the aggregation of particles. 

 Their impact would produce much heat, but 

 chiefly in the outer layers, where it would be 

 radiated away. 



(2) Mag^ietic elements would be more easily captured 



(the authors appear to favour the iron-core theory 

 of the Earth). Once an atmosphere was formed 

 the particles would be ignited on entering it, and 

 a large portion of them reduced to dust, which 

 would slowly settle down. Sifting of the material 

 according to its density would cause continental 

 elevations of lighter material and ocean floors 

 of heavier material. 



(3) Radio-active elements are invoked to explain volcanic 



phenomena. The work of Strutt, Joly, and others 

 is quoted in favour of the concentration of these 

 elements in the Earth's outer layers. 



BOTANY. 



By Professor F. Cavers, D.Sc, F.L.S. 



STRUCTURE OF BUD-SCALES.— The scales which 

 protect the resting buds of trees and shrubs are usually 

 regarded as the last leaves to be developed before the plant 

 prepares for its winter rest, the whole leaf or only part of 

 it showing arrested growth, and becoming modified for its 

 function of protection. Brick [Beih. hot. Centralbl., Volume 

 XXXI) has investigated the microscopic structure of the 

 bud-scales in a number of plants, comparing their anatomy 

 and development with that of the ordinary leaves in each 

 case, and has added various details to previous knowledge 

 of bud-scale structure. He finds that bud-scales resemble 

 leaves closely in origin and growth, but he draws a sharp 

 distinction between the inner scales and the outermost 

 (oldest) ones. The inner scales resemble leaves arrested in 

 their development, agreeing with ordinary leaves in micro- 

 chemical reactions as well as structure of the epidermis 

 and mesophyll cells and in the development of air-spaces. 



The outermost scales, however, have developed on divergent 

 Lines, starting at a very early stage, and fall into three 

 distinct groups, for the scale may originate from the rudi- 

 ment of either: (1) A whole leaf, (2) the basal part only 

 of a leaf, or (3) a leaf in which stipules are already developing. 

 The arrangement of the corky tissue in the outer scale is 

 described in detail, its distribution being such that the bud 

 is enveloped in a closed sheath of corky cells : these outer 

 scales have usually very reduced vascular tissue, so that 

 the scales receive a scanty supply of water, only sufficient 

 to enable them to develop into a protective structure, 

 and serve as a corky envelope around the inner portion 

 of the bud. 



CHEMICAL CHANGES IN GEOTROPISM.— It has 

 been known for some time that, when a root or a stem 

 is subjected to geotropic stimulation — that is, when it is 

 placed horizontally, and is receiving the gravity stimulus 

 to which it responds after a time by curving downwards 

 or upwards — chemical changes take place in the cells. 

 Eva Schley (Bot. Gazette, Volume LVI) has investigated 

 these changes in some detail, and obtained interesting 

 results, using Broad Bean seedlings. In a growing shoot the 

 acidity of the cell-sap is greatest at the tip, decreasing 

 downwards. \Vlien the shoot is geotropically stimulated, 

 the concave side becomes at first more acid, but the acidity 

 then diminishes until the greatest acidity is on the convex 

 side. When visible curvature has been made the two sides 

 again show equal acidity, and this condition remains until 

 the tip has become vertical. These changes in acidity are 

 not parallel with the relative rates of growth of the two 

 sides ; but that they are indicative of chemical processes — 

 as yet not fully investigated — taking place in the cells as 

 the result of geotropic stimulation is shown by the fact that 

 the percentage of dry weight is always greater on the 

 concave side. This is to be expected, since growth (involving 

 loss of material) is greater on the convex side when a stem 

 (or root) is curving under the stimulus of gravity. 



CHEMISTRY. 



By C. AiNSwoRTH Mitchell, B.A. (Oxon), F.I.C. 



ALCOHOL FOR INDUSTRIAL PURPOSES.— The 



development of many British industries has been severely 

 checked by the want of pure alcohol, free from duty ; 

 and it is only during the last year that the Excise Com- 

 missioners have altered the regulations so as to enable 

 manufacturers to compete on equal terms vnth their 

 foreign competitors. The current issue of The Journal 

 of the Society of Chemical Industry (1915, page 53) pubUshcs 

 these regulations as an official notice. The precautions to 

 prevent the improper use of such duty-free alcohol include 

 proof by the manufacturer that such spirit is essential to 

 his industry, control of the alcohol by a revenue officer, 

 and the addition to it of such approved substance as shall 

 render it unsuitable and unpalatable for drinking. Regu- 

 lations have also been made for the use of methyl alcohol 

 and petrol, free of duty, for industrial purposes. 



AMORPHOUS BORON AND MAGNESIUM BORIDE — 

 The so-called amorphous boron, as prepared from boron 

 trioxide and magnesium, has been investigated by Mr. 

 R. C. Ray [Chem. Soc. Trans., 1914, CV, 2162), who shows 

 that it is never free from oxygen and magnesium oxide. 

 The results obtained indicate that it probably consists 

 of a lower o.xide of boron, po.ssibly in combination with 

 magnesia, in a state of sohd solution in amorphous ele- 

 mentary boron. The magnesia may be removed by fusi-ig 

 the preparation with boion trioxide. The crystalline 

 variety of boron, which is approximately pure, does n;>t 

 enter into direct combination with magnesium, whereas 

 amorphous boron yields a boride corresponding to the 

 formula Mg;,Bj, which appears to be the only boride 

 formed by heating the two elements to red-heat under the 

 ordinary pressure. By heating this boride at a high tern- 



