136 NOTE ON ITACOLUMTTE OR FLEXIBLE SANDSTONE. 



cult indeed to see how to account for the stretching of the slab 

 when tension, and its compression when pressm*e, is applied. 

 I have recently been able to examine a specimen of flexible 

 sandstone in the possession of Mr. T. S. Hall, M..L., Acting- 

 Professor of Biology in the University of Melbourne, and in 

 this specimen both of the phenomena of extension and cona- 

 pression are present. After all, if the rock shows flexibility 

 when mica, chlorite and talc are either entirely absent, or are 

 quite subsidiary, it seems quite clear that the older theory 

 must be abandoned. 



The theory with which we have now to deal is, I believe, 

 the one usually accepted amongst modern geologists. Though 

 not without its own difficulties it is in many ways more con- 

 vincing than the one due to Von Eschwege. 



Mr. Oldham's view, as stated in his own words, ii that: 

 "the flexibility of the rock is due, not to the flexibility of any 

 of its constituents, but to .some peculiarity in the mode of 

 aggregation of the individual grains of quartz and other 

 material of which it is composed." A similar idea was put 

 forward by Klaproth § as far back as 1785, and at a later 

 date by the Rev." Dr. Haughton, F.R.S. 



Mr. Oldham appears to have carefully examined the rock in 

 thin microscopical slides. As a result of his labours, he 

 states : " If a slice of flexible sandstone is examined under the 

 microscope, by reflected light, it exhibits a structure most 

 conspicuous in all the specimens of flexible, and equally con- 

 spicuous by its absence from all sj^ecimens of non-flexible, 

 stone I have examined. The rock consists of irregular aggre- 

 gates of grains of quartz separated from each other by fissures 

 and crevices which extend deep into the stone and give one 

 the impression of ramifying through its mass further than 

 they can be actually traced. Should one of these aggregates 

 of quartz grains be touched with a needle it will be found 

 loose and easily moveable from side to side, but it cannot be 

 displaced without fracture, either of itself or of the surround- 

 ing particles. In fact the rock consists of a number of 

 irregular aggregates of quartz which hold together by 

 projections on one fitting into liollows in another, while the 

 clear space between them allows of a certain amount of play." 



Mr. Oldham gives two plates supporting his view of the 

 structure of the rock. Mr. Oldham then proceeds in develop- 

 ment of his theory as follows : — "In the Kaliuna rock there 

 is, besides the quartz and accessory minerals, a certain 

 proportion of felspathic paste, more consj^icuous in sections 

 cut transverse, than in those cut parallel to the bedding. 

 This paste does not surround the individual grains of quartz, 

 but occupies spaces between aggregates of grains, and it is 



I Schrift Berl. Ges. Natfur. Freunde VI., 322 (1785). 



