THE HAWKESBURY SANDSTONE. 73 
and some are over 300, their height depending on the thickness of 
the current of air. Pools of water are found on all the sand dunes, 
and often completely hidden by a coating of sand which does not 
sink, thus becoming a dangerous pitfall. These pools are carried 
_ wlong with the shifting sands, caused by the filling up with sand on 
_ meside, and thus pushing the basin along. The formation of lakes 
marshes in the French Landes is one of the most remarkable 
features in them. A row of ponds differing in shape and size but 
generally parallel with the coast, is prolonged over a space of 125 
miles. Some of these were originally at the sea-level, and are now 
66 feet above it. One covers an area of 15,000 acres. Much 
of this area has been reclaimed by planting pines. Sometimes 
the advance of the sand is arrested by circumstances which favoured | 
i¢ growth of vegetation, and at Arachon forests of gigantic pines 
have covered one sand tract, with oaks which were 46 feet in girth 
‘me years ago. On the other hand, there are plenty of places in 
Soma where there are traces of former forests now covered 
ics 
Ths we may expect to find in the Hawkesbury formation traces 
a of lacustrine deposits, with former marshes and lagoons. In these 
fishes would become entombed, and the way in which they are 
aoe ry this sandstone may be explained as follows :—In one of 
fe Stuart's expeditions he found in Lake Eyre, in the central desert, 
— when the waters had become very low, a number of small 
_ Stall dried and caked in salt. Now it is easy to see how in the 
: wy sands which form the shores of this lake, these fish might 
. hecle, ered by an advancing sand dune, and thus entombed as 
Wide, Here they formed a belt along the shore about 12 yards 
for the shale 
of fresh and 
