416 
ELEMENTS OF GEOLOGY. 
Dawson in a coprolite of a terrestrial reptile occurring in a 
fossil tree, no specimen of this class has been brought to 
light in the Joggins. But Mr. James Barnes found in a bed 
of shale at Little Glace Bay, Cape Breton, the wing of an 
Ephemera, which must have measured seven inches from tip 
to tip of the expanded wings—larger than any known living 
insect of the Neuropterous family. 
That we should have made so little progress in obtaining 
a knowledge of the terrestrial fauna of the Coal is certainly 
a mystery, but we have no reason to wonder at the extreme 
rarity of insects, seeing how few are known in the carbonif¬ 
erous rocks of Europe, worked for centuries before America 
was discovered, and now quarried on so enormous a scale. 
These European rocks have not yet produced a single land- 
shell, in spite of the millions of tons of coal annually ex¬ 
tracted, and the many hundreds of soils replete with the 
fossil roots of trees, and the erect trunks and stumps pre¬ 
served in the position in which they grew. In many large 
coal-fields we continue as much in the dark respecting the 
invertebrate air-breathers then living, as if the coal had been 
thrown down in mid-ocean. The early date of the carbonifer¬ 
ous strata can not explain the enigma, because we know that 
while the land supported a luxuriant vegetation, the con¬ 
temporaneous seas swarmed with life—with Articulata, Mol- 
lusca, Radiata, and Fishes. The perplexity in which we are 
involved when we attempt to solve this problem may be 
owing partly to our want of diligence as collectors, but still 
more perhaps to ignorance of the laws which govern the fos- 
silization of land-animals, whether of high or low degree. 
Carboniferous Eain-prints. —At various levels in the coal 
measures of Nova Scotia, ripple - marked sandstones, and 
shales with rain-prints, were seen by Dr. Dawson and my¬ 
self, but still more perfect impressions of rain were discov¬ 
ered by Mr. Brown, near Sydney, in the adjoining island of 
Cape Breton. They consist of very delicate markings on 
greenish slates, accompanied by worm-tracks {a, b, Fig. 444), 
such as are often seen between high and low water mark on 
the recent mud of the Bay of Fundy. 
The great humidity of the climate of the Coal period had 
been previously inferred from the number of its ferns and 
the continuity of its forests for hundreds of miles; but it is 
satisfactory to have at length obtained such positive proofs 
of showers of rain, the drops of which resembled in their av¬ 
erage size those which now fail from the clouds. From such 
data we may presume that the atmosphere of the Carbonif¬ 
erous period corresponded in density with that now invest- 
