12 LA TOUCHE : GEOLOGY OF WESTERN RAJPUTANA, 



with a talus of exceedingly sharp angular fragments at the foot of the 

 scarps (PI. Ill, fig. i) ; the more homogeneous bosses of intrusive 

 granite have their outer surface stripped off in concentric layers and 

 form hummocky domes with steeply sloping smooth sides, while 

 since the granite fragments are quickly broken up by the action of 

 the weather into a loose gravelly sand, little or no talus is formed at 

 the foot of the hills composed of this rock (Plates VI-VI1I) ; and lastly 

 the almost horizontal sandstones are carved into level plateaux, sur- 

 rounded by almost vertical scarps, wherever they rise to any appre- 

 ciable height above the plain. It is thus possible to form an opinion 

 of the character of the rocks of which any particular hill consists, - 

 even from a considerable distance, by observation of its form and the 

 appearance of the talus slopes at its foot. 



A peculiar feature in several parts of the country, especially in 

 those where the blown sand is not in great quantity, is the occurrence 

 at the base of each isolated rocky peak or knoll of a gently sloping 

 " glacis " extending to a distance of a mile or more from the foot of the 

 hill. Sections of these " glacis " are exposed in great numbers in the 

 numerous water-courses, dry except during an actual fall of rain, 

 which radiate in all directions from the hill, and cut deep channels 

 in the deposit. Their substance is seen to consist principally of a 

 calcareous tufa or " kunkur " frequently consolidated into bands of 

 considerable thickness, mingled with sand and fragments of the rock 

 composing the hill, in fact, a natural concrete. The kunkur gradually 

 diminishes in thickness towards the outer edge of the "glacis" and the 

 slope gradually fades off into the surrounding plain. The sand on the 

 level is also frequently impregnated with nodular kunkur, as may be seen 

 in the wells, but except near the hills this accumulation of calcareous 

 matter does not rise above the general level, and the formation of the 

 " glacis" is evidently connected in some way with the presence of the 

 hill. I shall refer to the source of the carbonate of lime from which this 

 kunkur is formed later on in the chapter dealing with the blown sand. 1 



1 Infra, p. \1. 

 ( 12 ) 



