Dr. Malcolm Maclaren — Desert-water in W. Australia. 301 



EXPLANATION OF PLATE XVI. 



FiBULARIA NIGERIiE, n.sp. 



Fig. 1. Adapical surf ace of A (type-specimen) . 



2. Adoral surface of A. x 4'5. 



3. Lateral view of A. x 4'5. 



4. Same specimen. Nat. size. 



5. Specimen B. Nat. size. 



6. Specimen C. Nat. size. 



7. Apical system of B. x 12. 



8. Peristome of B. x 12. 



9. B. post. amb. and iamb, of K. x 9. 



10. Ant. petal of B. x 9. 



11. Ant. petal of A. x 9. 



x4-5. 



IV. — Notes on Desekt-water in Western Australia. 

 ' Gnamma Holes ' and ' ]S"ight Wells '. 

 By Malcolm Maclaren, D.Sc, F.G.S. 



IN the arid region of the goldfields of Western Australia a know- 

 ledge of the conditions under which a search for water is most 

 likely to be rewarded is of prime importance to the prospector who may 

 find himself away from the beaten tracks. There is, in the summer, 

 little hope of finding fresh water in the long narrow bands of gold- 

 bearing greenstone-schist that run from N.N.W. to S.S.E. through 

 Western Australia, for both the surface and the deep-seated waters of 

 this rock- formation are then salter than those of the sea. When 

 unprovided with ' condensers ' for the distillation of these waters, 

 the prospector must therefore turn towards tlie neighbouring granitic 

 areas, and search either for * soaks ' or for the remarkable ' gnamma' 



Fig. 1. Cross-section of typical ' Gnamma ' hole. 



holes of the bare rocky ridges, 

 sources of fresh water — the 

 and requires little description, 

 at the foot of granite slopes. 



The first and most reliable of these 

 ' soaks ' — presents nothing abnormal 

 They are found in the sandy hollows 

 A well is sunk in the sand, and the 

 water is baled as it slowly percolates into the bottom of the hole. 

 The supply may vary from a mere trickle to several hundred gallons 

 in twenty-foiu' hours, according to the catchment, to the season, 

 and to the permeability of the sand that has protected the water from 

 evaporation since it was collected in the rock-hollow. 



Where the absence of soaks is indicated by the non-appearance 

 of the slightly greener vegetation that grows over them, the traveller 

 abandons the lower ground and searches the bare rock-outcrops 

 for rock-holes, or ' gnamma ' as they are called by the natives. 



