228 



NA TURE 



July 6, 1893 



opened by the gas was quickly closed again by the 

 rapidity with which the triturated rock resolidified. The 

 paper concludes with a suggested application of the 

 hypothesis to the cones and craters of the moon. 



In another paper M. Daubr^e returns to the subject of 

 the flow of rocks under high pressure. With respect to 

 this point he remarks that, in certain previous e.xperi- 

 ments, the rock not only accurately moulded itself to the 

 apparatus, but also formed thimble-shaped proluberances 

 outside it. Further experiments were conducted with 

 round plates placed one upon another, instead of the 

 former cylinders. Lead plates were first experimented on, 

 and then these along with plates of rock. One of the 

 most interesting results obtained was the production of 

 little " eruptive cones " of lead or rock outside the appar- 

 atus. In ons case the protuberance reached the height 

 of 36 mm. After the experiments, some of the plates were 

 found outside the apparatus in the form of circular cap- 

 sules, so closely fitted into one anoiher as to appear sol- 

 dered. Some of the lead plates remaining in the apparatus 

 were cut through in their central parts as with a punch. 

 The thickness of these perforated plates was found to be 

 diminished on their borders, and increased in their cen- 

 tral portions. This effect may be compared to what 

 occurs in many cases with contorted rocks. At the same 

 time spaces were here and there formed between the 

 plates thus united. Daubrde draws attention to the 

 analogy between these spaces and those occurring be- 

 tween separate strata among contorted rocks, and which 

 are often filled with metallic substances. Lamination 

 was also produced in the plates of rock. 



As a general designation for the accumulations of rocky 

 matter crowning the summits of all perforations in the 

 earth's crust opened by gaseous pressure, whether 

 trachytic domes, lava flows, scoris cones, or the kopyes 

 of South Africa, M Daubi(?e proposes the term 

 " ecphysema" (French, <?.'-;>/y.ft'/«<'," Gr , fKcfiva-rjua). 



To sum up M. Daubrde's results: — 



(i) High pressure gases from below are able to open 

 out channels in the earth's crust, by means of which the 

 same pressure can bring to the surface various products. 



(2) In forming such channels the gases may striate 

 and polish the walls of the perforations in a manner 

 recalling that of glacial action. 



(3) The products of such erosions are partly of the 

 nature of fine dust, which may be carried to immense 

 distances, and a part of which resembles exactly the so- 

 called cosmic dust. 



(4) That the same high-pressure gas can fracture, 

 break up, and pound a rock, and afterwards resolidify 

 the same. That in thus resolidifying, the broken-up rock 

 may mould itself accurately on the bounding walls of its 

 enclosure, so as to take their polish and the impress of 

 the striations upon them. And, further, that portions 

 may be thrust outside the apparatus in the form of pro- 

 tuberances of the nature of "eruptive cones." And 

 thus it may be conceived that, by the force of high- 

 pressure gas from below, rocks may be broken up and 

 reconsolidated z'« situto form breccias of diverse natures. 



Some further applications of the experiments may be 

 suggested. 



Thus they may perhaps explain the origin of those 

 remarkable natural pits of Hainaut, which have given 

 rise to much discussion. In their general structure 

 these pits are analogous to the diamond pipes of South 

 Africa. Like them they are more or less circular per- 

 forations in the rocks, of unknown depth, and filled with 

 rock debris. Since none of the explanations hitherto 

 applied to them seem satisfactory, perforation by high 

 pressure gas may be tried. 



Again, in certain of the experiments the faces of the 

 fissures in the cylinders of rock were found to be polished 

 and striated. The polishing and striation of rock sur- 

 faces in connection with faults is known as slickensides, 



NO. 1236. VOL 48] 



and ascribed to the movement of one surface over the 

 other. M. Daubree's results indicate the possibility that 

 certain slickensided surfaces may rather be due to the 

 energetic action of high pressure gas. In any case it is 

 perhaps a little difficult to understand how a single move- 

 ment of one rock surface over another — if we suppose a 

 fault produced by a continued movement in one direction 

 —could produce anything like a perfect polish. And it 

 cannot be denied that the above experimental result 

 shows the possibility of another cause. 



And further, if we accept .M. Daubrc^e's interpretation 

 of his results, we arrive at the remarkable conclusion that 

 gaseous bodies, given sufficiently high pressure and rapid 

 motion, can polish and striate in a way generally supposed 

 to be confined to solid bodies. This, indeed, is in con- 

 formity with the general results of advanced physical 

 research which tends to show that, under sufficient pres- 

 sure, hard and solid bodies can be made to act as liquids, 

 while soft and even gaseous bodies, if endowed with 

 sufficient force and speed, act like solids. 



If, then, a gaseous body, under certain conditions of 

 speed and pressure, can polish and striate a rock without 

 the intervention of solid particles, is it not possible that 

 ice, given certain conditions of speed and pressure, may 

 likewise striate and polish without the graving tools 

 usually considered necessary ? The conception of an ice- 

 sheet, or glacier, moving over the rock surface of the 

 country with a series of pebbles and boulders firmly 

 frozen into its lower surface is difti'cult to reconcile with 

 the physics of ice masses in motion. Hence it seems 

 worth while to make a trial application of the experi- 

 mental results in this direction likewise. Even if we do 

 not accept M. Daubree's view that the striation of the 

 rock surface was accomplished by the gas alone, and hold 

 that the intervention of solid particles was required, there 

 is still a possible application to glacial action. For if 

 solid particles simply carried along by a rapidly-moving 

 gas can produce parallel striations, may not particles 

 simply carried along by the ice do likewise without being 

 held firmly frozen into its mass ? On either view, in 

 fact, a difficulty in the conception of how a glacier striates 

 and polishes is removed. 



: ^NOTES. 



The professors of the University of Melbourne have inter- 

 viewed the Premier on the subject of the decrease in the grant 

 to that institution. They said that there was no possibility of 

 reducing the present staff, as it was not overmanned. Many of 

 their number had come to the colony under special contract with 

 the authorities of the university, and it would be a serious matter 

 if faith were broken with them by insisting on a reduction in 

 the' r salaries. Mr. Patterson replied that these were times of 

 retrenchment, and it was right that everybody should contribute 

 something to pull the country out of its difficulty. It appeared, 

 however, that the University had been cut down ;^5000last year, 

 and it was further proposed to reduce the expenditure on the 

 institution by ^3000. lie reiterated generally the statement 

 made by the Minister of Education on tlie subject of re- 

 trenchment, but he promised to hold a consultation with 

 Mr. Campbell, with the view of ascertaining if anything could 

 be done in the matter. He thought it possible that Mr. Camp- 

 bell, on taking a review of the special circumstances of their 

 case, might see his way to some abatement of the rigorous course 

 which had been proposed. 



A MEETING of the Executive Committee of the Rothamsted 

 Jubilee Fund was held on Monday, the Earl of Clarendon in 

 the chair. On the motion of theChaiiman, the Duke of Devon- 

 shire, as the incoming President of the Royal Agricultural 

 Society of England, was added to the Committee. Sir John 



