THE LIVING WORLD. 
25 
yet fifteen years since the use of electricity as an illuminator was unknown, 
and yet think for a moment of the extent to which its secrets have already 
been discovered and the many forms in which it is made to serve the needs 
and pleasures of mankind! But the coral insect serves mankind not solely by 
furnishing habitations ' for human beings. It is used not only for ornament, 
but its skeleton is, in its fossiliferous forms, the source of supply for the 
Tripoli powder so necessary in the mechanical arts for the uses of polishing 
metals. In Virginia the city of Richmond rests upon a stratum of coral 
of twenty feet in thickness. 
Chili abounds in coral remains, and in addition has near Copiapo a beach 
now removed almost a mile from the shore and elevated nearly two hundred 
feet above the level of the sea; moreover, the transformation of this coral island 
into stone is even now going on under the very eyes of living beings. It is 
thought that fuller investigation will show that, in addition to the ordinary 
classes of aqueous, igneous, and metamor- 
phic as divided by the physical geogra¬ 
pher, we must add coralline rocks as com¬ 
posing much the greater portion of the 
earth’s crust. 
Huxley has compared the way in which 
corals build to that of the ancient dwellers 
around the Mediterranean, who erect one 
city upon another, as Schliemann has shown 
by his excavations in search of the famous 
city of Troy. Students of physical geog¬ 
raphy will remember that sometimes the 
coral builds a “ fringing reef,” or one which 
surrounds an island and is separated from 
it by lagoons of relatively shallow water; 
that again it constructs an “ encircling 
reef” or “atoll,” which almost surrounds 
an island; and that yet again it makes 
an “ encircling reef,” or one which must 
have been formed about land as it sank. 
There is at Mauritius a fringing reef 
one hundred, miles in circumference;, and an encircling reef eleven hundred 
miles long. . 
The Nautilus, and in fact all the species which compose the order now 
known as Cephalopoda , are direct descendants from the ancient bellamites and 
numullites whose fossil remains are strewn so plentifully over the whole globe. 
Concerning this fact Rev. William Buckland, D. D., makes the following obser¬ 
vation^ £ rom the view we } iave ta k en 0 f the zoological affinities between 
living and extinct species of chambered shells, that they are all connected by 
one plan and organization; each forming a link in the common chain, which 
unites existing species with those that prevailed among the earliest conditions 
of life on the globe; and all attesting the identity of design that has effected 
so many similar ends through such a variety of instruments, the principle ot 
whose construction is in every species fundamentally the same. 
NAUTILUS IN THREE POSITIONS. 
