From the INTRODUCTORY.
IN any discussion of the constitution of the Atom the phenomenon of crystallization must have an important place, and it may be justly said that no theories of atomic or molecular constitution, which ignore the facts connected with the crystallization of the Elements, can be considered as resting on a sound basis.
When an elementary substance is in a gaseous condition enclosed in a vacuum tube and subjected to forces relatively of great magnitude, there must necessarily be great difficulty in separating the phenomena produced by these conditions and by the rapid movements (both rotational and translatory) of the atom, from those characteristics that belong exclusively to the atom itself. If these characteristics are studied then the atoms are in a state of approximate rest, they afford a much more satisfactory field for investigation, and more reliable results may be expected.
The following statement of facts in connection with the crystallization of elementary substances is submitted.
(1). A large proportion of the Elements are known to assume a crystalline structure when in the solid state, and of those which are not so known, many are capable of forming crystalline space-lattices when in combination with other Elements.
Some elementary substances which are liquid or gaseous at Ordinary Temperatures, may not have been examined in the solid state under conditions which produce the crystalline form.
(2). Of those Elements which are known to crystallize each one forms its own particular crystal or space - lattice. Some elements crystallize in more than one geometric form, but these cases do not invalidate the general rule stated above.
(3). Crystal formation is not affected or controlled in any way by physical forces other than heat, pressure and solubility. Electricity plays no part in the formation of a crystal, and a magnetic field has no effect upon the process.
(4). The space-lattices vary as regards density; i.e., the atoms are more closely packed in some crystals than in others. Sulphur forms crystals in two forms — Rhombic and Monoclinic, the latter readily changing into the Rhombic form with a marked change of volume at the transition point.
It is difficult to conceive of spherical or ellipsoidal forms having the power to arrange themselves according to geometric laws so soon as the vibrations of heat are reduced to a certain degree, and in the absence of any other directive force so far as is at present known, but if the atoms themselves have definite geometric forms, then arrangement in an orderly space-lattice, so as to produce definite geometric figures peculiar to each atom, appears to be the natural result of the withdrawal or reduction of the vibrations of heat.
