The Coal Measures. 
20 !) 
lavas. Thus the sea has again receded and given place 
to fresh water. No marine fossils have ever been 
found in the great thickness of sediments known as 
the Upper Coal Measures. 
North, as far as where Newcastle stands, west to 
Mt. Lambic and Rylstone, and south to Nowra, there 
stretches one unbroken and marsh-like plain. PhyU 
lotheca, Glossopterks and other ferns, cover the surface 
in the wildest luxuriance. Our last look into those 
far-off times shows us the great Permo-Carboniferous 
morass still subsiding. A richer growth, if anything, 
clothes its wide expanse. Sluggish and swollen rivers 
wind their way through the monotonous level, and 
disappear in the tangled undergrowths, there depositing 
their loads of sediment to form yet one more layer on 
the thousands already laid down. Such were the 
physical features of the country around Sydney at the 
close of the Permo-Carboniferous period. 
One ot the charms of the study of geology is 
that, while it deals with the plainest matters of fact, 
it continually calls up to the imagination pictures of 
past events, of which the general truth is certain, 
while all the details are left to fancy. That the lime- 
stones oi t he Carboniferous period were formed beneath 
the waves of a widespread sea is as certain a fact as 
that they now form the lofty cliffs, at the foot of which 
the geologist pauses to examine them. The fossils 
they contain are the remains of animals that once lived 
and sported in those waves. The shales and sand- 
stones were derived from the waste of the lands on 
