82 THE HAWKESBURY SANDSTONE. 
the whole debris carried as alluvium into the plains below, At first 
Mons. Virlet-d’Aoust imagined that this was an alluvial formation, 
derived from the washings from the mountain sides. But the 
deposit was found to cap the isolated mountains. It could not 
have been upheaved, for it was horizontal, and in any case included 
fragments of pottery and articles of human manufacture, besides 
wood and plant remains. As for its recent upheaval by volcanoes 
none of them have reached the height at which this deposits 
found. At last a sufficient cause was found in the dust-stomis 
which are exceptionally violent and frequent in this region. 4H 
whole plateau is distinguished by immense whirlwinds of wr 
ge FT. seg es 2 OS RT 
d 
yellowish cloud from the quantity of dust remaining suspended. 
n ot give all the arguments or the details of the facts 
one. The able observer who thus explains the formation Om 
Dr. Macgowan describes one which lasted several hours, and Ww 
so dense as to hide the sun. ‘cal “7 
At Fontainebleau.—The sandstone of Fontainebleau 8 ™ i 
by most geologists to be a formation derived from sand-dunes 
contains beds of shale and lignite, and a peculiar hydro e ihe 
called “alios,” which is also found in the sand-dune “| 4 
Landes.* The sandstone referred to occurs at Cernay, obsess : 
there and in many other places it is distinguished by the ® é 
of level horizontal and regular stratification coe ae is 
e 
iD 
dstone 
support of such an origin for these rocks and the sam oct 
Rilly. He says that the suggestion of their eolian. org pen We 
to the mind at once, but this idea becomes a certainty © 
dite Baath dike boars 
et “bac vél. 59, p. 64, Also an analysis of the | te 
+ Comptes rendus, vol. 85, p. 1240. a 
#: 
