“The infinite groups of atoms, flying through all time and space in different directions and under different laws, have interchangeably tried and exhibited every possible mode of rencounter: sometimes repelled from each other by concussion, and sometimes adhering to each other from their own jagged or pointed construction, or from the casual interstices which two or more connected atoms must produce, and which may be just adapted to those of other figures,--as globular, oval, or square. Hence the origin of compound and visible bodies; hence the origin of large masses of matter; hence, eventually, the origin of the world itself.”--Dr. Good’s _Book of Nature_. [36] Young’s _Lectures on Natural Philosophy and the Mechanical Arts_. Lecture 49, _On the Essential Properties of Matter_. CHAPTER V. CRYSTALLOGENIC FORCES. Crystallisation and Molecular Force distinguished--Experimental Proof--Polarity of Particles forming a Crystal--Difference between Organic and Inorganic Forms--Decomposition of Crystals in Nature--Substitution of Particles in Crystals--Pseudomorphism--Crystalline Form not dependent on Chemical Nature--Isomorphism--Dimorphism--Theories of Crystallogenic Attraction--Influence of Electricity and Magnetism--Phenomena during Crystallisation--Can a change of Form take place in Primitive Atoms?--Illustrative Example of Crystallisation. “Crystallisation is a peculiar and most admirable work of nature’s geometry, worthy of being studied by all the power of genius, and the whole energy of the mind, not on account of the delight which always attends the knowledge of wonders, but because of its vast importance in revealing to us the secrets of nature; for here she does, as it were, betray herself, and, laying aside all disguise, permits us to behold, not merely the results of her operations, but the very processes themselves.”--Such is the language of an Italian philosopher, Gulielmini; and it is the striking peculiarity of beholding the process of the formation of the regular geometric figures of crystals, the gradual accretion of particle to particle, which induces us to separate crystallization from mere molecular aggregation. Without doubt the formation of a crystal and the production of an amorphous block are due to powers which bear a close resemblance in many points; but they present remarkable differences in others.