H. P. Woodward — Dry Lalces of W. Australia. 365 



sediment deposited upon each occasion that these flats are covered 

 by flood-water, but also a quantity of salt. 



It would be only natural to suppose that in countless ages, these 

 deposits would assume a considerable thickness ; but this is not tlie 

 case, for do we not in many places find the upturned edges of 

 the very oldest known rocks forming the beds of these lakes, and 

 where they are covered, it is only by a thin deposit of clay. After 

 looking into the reasons for this, we first notice that the salts 

 deposited upon these surfaces consist very largely of gypsum, which 

 upon crystallizing out in the clay causes it to split up, thus allowing 

 the weather to act upon it, which quickly converts it into an almost 

 impalpable powder, which the wind distributes far and wide over the 

 surface of the country, whilst the sand and heavier particles are 

 blown along the surface until they meet with some obstruction, 

 where they accumulate to form sand-dunes, hills, and ridges. 



It will naturally be asked why, if these lake-beds are formed by 

 wind and not by water, they should assume such a dead level. The 

 answer to this is — that the subterranean water is always so near 

 the sui'face that the moisture rising from it by capillary attraction 

 holds together the particles, thus preventing either the superficial 

 deposits or the disintegrated rock below a certain level from being 

 removed by the wind. 



The formation of the cliifs around these lakes would probably 

 start in the same manner that the " break-aways " are being formed 

 at the present day, viz. : by the action of the water thrown from 

 the hard impervious cement-hills, which has not only cut out 

 the canyon-like channels thi-ough them, but also into the de- 

 composed rocks below to the lake-bed level. The resulting debris 

 from this source, as well as that which falls periodically from the 

 cliff-faces, must then have been removed by the wind, because no 

 trace of it remains upon the clean-swept rock-bottomed lake-bed. 

 This action goes on year after year. The rain falling upon the 

 surface of the ground dissolves out the salts which the water carries 

 in solution, together with the insoluble sediment in suspension, 

 redepositing them upon these plane sui'faces where they dry, and 

 efflorescence being possibly added to by a small portion of the dis- 

 integrated rock-surface of the bed itself, this fine material is again 

 scattered over the surface of the land by the wind. 



Thus the country remains salt, since no streams carry away the 

 saline matter to the sea, whilst the underground percolation of the 

 water is so extremely slow that in millions of years no appreciable 

 difference in its saltness seems to have taken place. 



The subterranean water beneath these lake-beds is abundant and 

 extremely salt, often containing as much as forty ounces to the gallon, 

 but it varies considerably in quality, for the further a well is removed 

 from these salt clay-pans, and the higher the elevation attained, the 

 fresher the water becomes; thus, beneath the high sand-plain, or 

 the elevated pervious caps of disintegrated granite, perfectly fresh 

 water is often met with because from them the salts have been 

 completely leached out, whilst they are not resupplied, since their 



