125 



is in a high state of decomposition, so that stone of this kind, 

 though containing much silica, is, nevertheless, exceedingly 

 friable ; and when such is used for road metal the percentage 

 of argillaceous matter is altogether insufficient to hold together 

 the more indestructible, but incohesive, particles of silica. 

 Roads constructed or repaired with such material always 

 present during our hot and dry summer months a rough and 

 gritty surface, every casual puff of dry wind renewing the 

 grating powers of the rasp. 



'Fundamental Limestone. — With all due respect to the opinion 

 of the members of our various Road Boards, District Councils, 

 and superintending officers, I am persuaded that they would do 

 well to direct greater attention to this class of material for 

 road-making and mending purposes. Being fully convinced 

 that the metamorphosed limestones of G-awler Hill are 100 per 

 cent, more durable for road purposes than many of the 

 quartzites used, I venture to suggest to those in authority that 

 the marbles should have at least a fair trial. 



Travertines. — Except where the traffic is light, or for 

 blinding purpose, those of Munno Para are not adapted for 

 road construction. 



Clay-slate. — The harder sorts, when broken to 4 inch gauge, 

 make a very fair foundation for new roads. Also, I am of 

 opinion that a mixture — say of one to six or eight — broken up 

 with quartzite, would tend to bind and prolong the wear of 

 that material greatly, having seen the highly decomposed 

 specimens of that rock used to great benefit in blinding over 

 quartzite metal. 



Springs issuing prom the Fundamental Rocks. 



Probably no like extent in South Australia can boast so 

 goodly a number of surface springs of excellent water as can 

 Munno Para East. To obtain that happy condition the 

 country must necessarily possess the following qualifications : — 

 Eirst, an absorbent super-stratum ; second, a moderately 

 retentive sub-stratum. These geological characteristics Munno 

 Para East naturally possess in a marked degree, therefore it 

 behoves the occupants of the soil to see that these natural 

 gifts are not infringed upon. 



In a former part I had occasion to direct attention to the 

 exceedingly absorbent properties of the Upland Miocene bed. 

 My object now is to show how the waters directed from the 

 surface by the action of these beds into subterranean channels 

 again re-appear at the surface in the shape of refreshing springs. 

 A glance at the map will show the absorbent, or Miocene, beds, 

 chiefly occupying the higher tracts. Rainwater falling upon 

 this superficial sponge soon penetrates beyond the influence of 



