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POPULAR SCIENCE REVIEW. 
there is any elevated coral reef rock around the shores of Hawaii, I would 
reply that I think not. I have travelled the whole circuit of the island by 
land, and in boats, canoes, and larger vessels, and there is hardly a point 
along the shores which I have not noticed carefully. Honolulu, on the 
island of Oahu, is built much of it upon the elevated coral reef rock, and 
there are large areas in the district of Waianse and other portions of the 
Oahu shores; but there is nothing of this kind on Hawaii. You are aware 
that corals, even under the water, are on the weather side of this island [the 
eastern, near the middle of which is the harbour of Hilo], not abundant, 
and all the good specimens we get are obtained by diving. Small quantities 
of broken corals are washed ashore by the waves.’' The Oahu reefs are de- 
scribed by me in my Exploring Expedition Geological Report, pp. 251-256. 
The facts are more briefly mentioned in my work on u Coral and Coral 
Islands.” 
How is Flint formed , and how does it operate in Fossilisation? — These 
are two questions which have not yet been satisfactorily considered, especi- 
ally the latter one. However Dr. 0. Ward has attempted an answer in a 
paper, read Nov. 20, 1874, before the Eastbourne Natural Hist. Soc. After 
discussing the mode of experimenting performed by Dr. Richardson, he 
says : “ These discoveries and experiments of Dr. Richardson seem to me 
to be likely to throw great light upon several geological facts not hitherto 
explained. First, they explain how flints may be formed and deposited 
upon organic substances; next they explain the greater hardness of the 
matrix immediately enveloping fossils; thirdly, they account for fossils 
being so frequently found in the centre of a nodule, the materials of which 
are arranged in concentric layers ; lastly, they explain the absence of fossils 
from metamorphic rocks ; for if we can destroy nearly all traces of organisa- 
tion in a few hours, and with a low temperature of 340 degrees F., there 
can be no difficulty in understanding how rocks full of fossils may entirely 
change their character, and chalk or tertiary limestone be converted into 
marble of a perfectly homogeneous appearance in contact with lava and 
other igneous products as are found at the Giant’s Causeway.” 
A Fhonolite from the a Wolf Rock.”— Mr. S. Allport again refers to this 
subject in the “ Geological Magazine,” for October, 1874. He says that in 
the “Geological Magazine,” vol. iii., 1871, p. 247, he gave a short account of 
the composition and structure of a Phonolite which forms the mass of the 
“ Wolf Rock,” lying between the Land’s End and the Scilly Islands. The 
account there given has been noticed by Prof. Zirkel, in a work recently 
published, in which he refers to his (Mr. A.’s) description of some of the 
crystals stated to be nepheline, and suggests that they may be nosean. The 
passage to which he refers is as follows : 11 The grey dust filling some of 
the crystals is frequently collected together so as to form a dark or even 
black mass in the centre, the edges of which are sharply defined, and 
correspond exactly with those of the crystal. Hexagonal crystals, for 
example, exhibit a border filled with a fine grey dust, and a central por- 
tion occupied by a well-defined black hexagon, or there is sometimes a 
black band running parallel with, and at some distance from, the sides.” 
To this Mr. Allport now adds, that some of the crystals and irregular 
grains are traversed by a number of very fine straight lines of a bluish 
