At about 

 was reached 

 appearance. 



79 



with tlie adjacent Tomkinson Range to the north, it consists of a 

 porphyritic rock. Moses Creek, which debouches on the eastern 

 plain, lias a very short course. It is here we found a tree which 

 had successively been blazed by the explorers Gosse, J. Forrest, 

 and Mills. 



oO miles from Skirmish Hill the Cavenagli Range 

 The intervening country was of the most desolate 

 Travertine and sand-dunes abound, interrupted only 

 bygone low granitic ridge, much intersected by quartz-dykes. In 

 this granitic ridge occurs a rock-hole of most peculiar shape, 

 which yielded us several hundred gallons of water. It is in the 

 form of a narrow channel about two feet wide and about seven or 

 eight feet long, sloping to the west, then extending easterly into 

 a horizontal chamber some six feet wide. Close to this rock -hole 

 I found under some sheltering rocks an abundance of flint- and 

 chalcedony-chips, apparently the refuse from the manufacture of 

 stone-implements. Intermingling with these were marsupial- 

 bones, so that the whole constitutes a veritable "kitchen-midden." 

 Similar accumulations I had noticed at Camp 20, which was also 

 near a big waterhole, and at Camp 23, in the Barrow Range. 



The Cavenagh Range, which rises in Mount Cooper to 2,175 

 feet above sea-level, is composed of plutonic and trappean rocks ; 

 the interspersed wide valleys are well-grassed, and each is 

 generally traversed by a creek. E. G-iles records,* during his 

 four or live days' halt in this neighbourhood in the month of 

 December, the daily passage of an earthquake-wave at about .3 

 p.m., accompanied by "the sounds of smashing and falling of 

 rocks hurled from their native eminences, rumbling and crushing 

 into the glen below," coincident with which on one occasion was 

 a temporary interruption to the flow of water from a spring. 



The very compact diorites of the higher part of the range are 

 weathered into immense boulder-like masses and bosses, the 

 former of which are sometimes poised on top of one another in a 

 very extraordinary manner. It is therefore highly probable that 

 some of these poised-blocks, expanding under the iniiuence of the 

 fierce sun of a Central Australian summer, do lose their equili- 

 brium, and, tumbling down, cause a regular mountain-slip, which 

 may for some time block the flow of a weak-running rivulet. The 

 coincidence in time of the daily occurrence of the so-called earth- 

 quake-shock with that of the most intense heat lends support to 

 my explanation of the cause of the phenomenon and its periodic 

 recurrence. Moreover, with the view to the fullest investigation 

 possible to me, I erected a kind of seismograph, after the plan of 



Geographic Travels in Central Australia, p. l.'!2. 



