REPORTS OF RESEARCH COMMITTEES. 329 



{}) Sheet-flows or Sheet-floods. — Jutson (24) divides sheet- 

 flows into three tyj>eis — the rill type, the smooth-bottomed 

 valley type, and the furrowed-floor type; and regards them as 

 agents of deposition rather than of erosion. 



' (/i) Gn^-mnui {or Natural Fork) Holes and " DimqAing " of 

 Grianite. — Talbot (35) believes these holes originated either 

 by disintegration of soft portions of the rocks or from a 

 shallow crack. Decomposition proceeds, and the lower 

 animals and man scoop cut the material. Woodward (39) 

 gives a. very similar explanation. Jntson (26) describes the 

 " dimples" on granite hills due to certain types of rock holes 

 or basins. 



{1) Diist Whirls. — Jutson (25) gives a record of dust whirls 

 personally observed, shows that they rotate both clockwise 

 and anti-clockwise, and discusses their relation to erosion. 



(???) Ram " Clawing," Gravitational Rock Drift, and 

 Miniature Soil Terraces. — Jutson (21) describes the peculiar 

 " clawing "' action of rain on soils with a somewhat hardened 

 surface, by which miniature soil terraces are formed, and by 

 which the slow gravitational drift of rock fragments is aided. 

 He also (27) describes an example ol the peculiar gravita- 

 tional drift in parallel lines of quartz fragmenl:s. 



(?i) Origin of Certain Rounded Pebbles. — Montgoauery (31) 

 suggests that while such pebbles may in some instances be 

 weatherworn, but not waterworn, or be residual pebbles from 

 the Nullagine conglomerate, others may be the result of the 

 action of moving water [apparently by the sea, and thus indi- 

 cating recent submergence]. Jutson (23) shows that certain 

 pebble® are now originating under present atmospheric in- 

 fluences, of which the direct beating action of rain is import- 

 ant. He concludes that no inferences of past fluviatile, 

 lacustrine, or marine action can be deduced from the pebbles 

 obseirved by him. 



(o) Rock Expansion and Disintegration by Temperature 

 Variation. — Woodward (39) describes this process as charac- 

 teristic of arid Western Australia, and Jutson (22) notes a 

 striking example. 



(p) S'nudl Intumescences on the " Dr>/ " Lake Surface. — 

 These have been noted by Saint-Smith (33), and by Jut- 

 son (15). 



4. Peneplains. — Jutson (14) inclines to the opinion that the 

 old plateau of Western Australia is a vast, uplifted peneplain, 

 which he described as the " Great Peneplain of Western Aus- 

 tralia " ; and Gregory (5) and Woolno<ugh (44) agree with this 

 idea. Jutson (14) describes the more coastal portions of this pene- 

 plain under separate nameis, such as, e.g., the Darling Peneplain, 



