308 The American Geologist. May, i890 
itself." Indeed ! supports itself. Would it -not have been 
much simpler to make the world self-supporting at once? 
Why introduce the elephant and the tortoise? They explain 
nothing ; on the contrary, they only increase the world's weight 
and our difficulty. 
The "angular hypothesis" which maintains tliat the funda- 
mental form of a crj'stal is determined by the shape of its in- 
tegrant molecules, has very few adherents now, and is practi- 
cally a thing of the past. On the other hand, the example of 
the spheroidal form of the planets, the tendency which liquids 
and even gases manifest to assume the spherical shape^ and 
the mechanical facilities which the hypothesis of rounded par- 
ticles offers in the grouping of molecules, have induced later 
inquirers to adopt almost unanimously the views of Wollaston 
and Hooke. We are now in a position to show, by cir- 
cumstantial evidence — at least as weighty as that from which 
we infer the existence of a luminiferous ether — that molecules 
must be more or less spherical, and in the case of "augmented 
molecules" alluded to in the foregoing, viz., the minute parti- 
cles of Avhich crystals are composed, we have abundant direct 
proof of this, as their forms are revealed by a magnification of 
less than 1500 diameters. 
But there is no reason whatever why the form of a molecule 
should not be capable of variation within certain limits. Why 
should it be absolutely constant? The conception of particles 
which under all circumstances preserve their outlines fixed 
and rigid is more difficult than that of particles which mani- 
fest a certain plasticity, and, with an elastic molecule as our 
starting point we can account for all the phenomena of crys- 
tallogenesis. It will be shown anon that this is more than an 
arbitrary hypothesis ; molecules, when uninfluenced by exter- 
nal agencies, assume the spherical form, but pressure, whether 
exerted upon them by mechanical or polar forces, causes pro- 
portionate changes of outline. If once we can establish the 
precise character of these forces, Ave can, with comparative 
ease, determine the shape of each molecule in a given crystal. 
Symmetrical forms must necessarily result from forces equally 
exerted along particular lines or planes. If we compress a 
number of elastic rubber-balls, we observe that they assume 
oblong, hexagonal, cubical and even tetragonal forms, accord- 
'Yide Pereira. 
