384 Bibliography. 
purpose as magnesia: which is not surprising, as the two substances are 
isomorphous. 
“Prof. W. B. Rogers, of the University of Virginia, has analyzed 
within the last six years upwards of a hundred specimens of cement 
rocks derived from the carboniferous and Apalachian series of Vir- 
ginia. and other states ; and he believes the cause of the solidification 
of the products, obtained by calcining both those classes of rocks, to 
be the formation of silicates: in the former chiefly those of lime and 
oxide of iron; in the strikingly hydraulic Apalachian limestones, those 
of lime and magnesia.” 
In Vol. xiv, p. 80, we have given from Dr. Beck’s Report on the Min- 
eralogy of New York, a table of analyses of the hydraulic limestone 
of that state, together with some general remarks on this subject. 
7. Dissertation on a Natural System of Chemical Classification ; by 
Otiver Wotcorr Gisss, of the city of New York.—In this work the 
author proposes a new and complete system of chemical classification 
for the elementary bodies founded on their analogies, in crystalline 
form er isomorphism, their relations to each other in their mode of 
combination and the molecular type of their compounds. 
He remarks, “‘ Between the fifty six elements to which all matter has 
been resolved, there exist numerous remarkable analogies which separate 
them first into subordinate natural families or groups, and then by gen- 
eral, though not indistinct resemblances, unite them into one indissoluble 
chain, each link of which differs in degree rather than in kind from its 
fellow on either side, so that the whole illustrates, in unorganized nature, 
the truth of the maxim of Linneus—: Natura non facit saltum’—Na- 
ture makes no leaps. And this, then, we assume as the fundamental 
idea and central point of our essay ; namely that this law of grades, 
which Linnzus announced for the organized kingdom alone, is an uni- 
versal law, and prevails as well among shapeless atoms as among living 
beings, and in the simplest crystals as well as in the innumerable com- 
plex forms in which life outwardly manifests itself.” 
The author here alludes to some of the points in which analogies 
may be shown to exist; and first, the relations which exist between 
the equivalents of bodies, which are such that a natural group of ele- 
ments have generally either the same equivalent, or else the relation of 
their equivalent numbers may be expressed by a very simple relation. 
This resemblance is too marked and general to be regarded as mere 
coincidence. 
“Tf we admit that the specific gravities of bodies represent the rel- 
ative weights of equal bulks, it follows, that if we divide the specific 
gravities by the atomic weights, we obtain the relative numbers of 
