228 NATURAL SCIENCE. ^,^y 



The sleeping and waking movements of leaves of several legumi- 

 nous plants were also studied. The leaf observed was usually covered 

 with lamp-black, and then a little flour put on the apex, which was 

 thus able to register the movements. To obtain separate records of 

 the repeated upward and downward movements, it was also necessary 

 to place the plant on a slowly revolving plane. By this means the 

 authors find that the apex of the moving leaf describes a series of 

 very regular oscillations. It arrives, by a series of downward and 

 upward movements, at the state of repose on which it enters by a 

 rapid succession of slight tremulous movements. There are always, 

 between the state of repose and the normal, two distinct periods, 

 which the authors term phases oi oscillation and tvemulation respectively. 



Experimental Researches on the possible Action of Gas at High Tem- 

 peratures, ACCOMPANIED BY VERY GREAT PRESSURE AND VERY RAPID MOVE- 

 MENT, IN VARIOUS Geological Phenomena. By A. Daubree. Bull. Soc. g'eol. 

 France [3], vol. xix., p. 313 (1891). 



M. Daubree, the well-known author of Geologie Experimentale, has 

 turned his attention to the geological action of gas at high tem- 

 peratures and pressures. 



Charges of dynamite and gun-cotton were exploded in a small 

 chamber, the orifice of which was closed by cylinders of rocks of 

 various kinds, such as granite, limestone, basalt, trachyte, and the 

 Pultusk meteorite. The pressures realised in the experiments 

 varied from 1,100 to 2,300 atmospheres, and the temperatures were 

 estimated to range from 2,500° C. to 3,200° C. It was found that 

 rocks of various kinds could be readily perforated, and that the 

 channels by which the gas escaped were striated. Vertical pipes 

 or " necks," such as those in which the diamonds of South Africa 

 occur, are believed to have been formed in this way. The striations 

 on the sides of these pipes, and the absence of contact metamorphism 

 in the surrounding rocks, are easily explained on this hypothesis. 



The nature of the powder produced by the pulverisation of the 

 rocks was examined by placing a piece of cardboard coated with 

 vaseline some distance above the orifice. The larger fragments 

 perforated the cardboard, but the minute particles were retained by 

 the vaseline. They were found to consist of angular fragments of 

 the constituents of the rocks, quartz, felspar and mica in the case of 

 granite, and small opaque, or nearly opaque, globules bearing a 

 striking resemblance, at any rate so far as form and size are con- 

 cerned, to the so-called cosmic spherules of the deep-sea deposits.' 

 The author does not deny that the passage of meteorites through the 

 air must be accompanied by the formation of such globules as those 

 described by Messrs. Murray and Renard, but he points out that 

 terrestrial agencies may also be concerned in their production. 



One of the most striking results of the experiments is the proof 

 that, in the extremely minute fraction of a second, during which 

 active change is going on, rocks may be moulded to the form of the 

 surface against which they are pressed. This moulding is so perfect 

 that the stria; left l)y the tool used in turning out the cavity in the 

 mass of steel are reproduced on the rock. Microscopic examination 

 shows that this plasticity is due to the fracture and re-cementation of 



' See Natural Sciknce. No i, p 21. 



