THE POPULAR SCIENCE MONTHLY.
themselves, to science, and to the countries which have welcomed them, in proportion as rulers have had the good sense to leave them time to work.
Democracies encourage savants most by leaving them the widest liberty of opinion. They have furthermore the advantage of causing the separation from political life and public functions of those men who have taste for research, cabinet-work, independence of thought, and for the truth as set above popularity and material considerations, or for precisely those things which most further the advance of science. In general, whatever may be the form or the tendency of the government, men who cultivate science for itself should rather consider themselves fortunate if they are out of favor with the administration.
|THE PROBLEM OF CRYSTALLIZATION.|
By ALFRED EINHORN, Ph.D., M. E.
CRYSTALS are symmetrical forms bounded by plane surfaces. A surface is said to be plane or level when its nature is such as is exemplified in a sheet of water extending over dimensions very small when compared to the radius of the earth. Crystals occur abundantly; they are generally diminutive and frequently microscopic in size, and therefore readily escape ordinary observation. Quite different in this respect are many forms caused by the rougher forces active in Nature, and analogous to crystals in the regularity of the shapes they assume. They are not unfrequently noted for their unique and startling appearance, as is instanced in the five-sided columns of basalt, known in some volcanic regions, and distinguished for their weird forms and the awe and superstition they give rise to among the inhabitants. Also many erosion figures resulting from the disintegrating action of water and air upon rocks. Many examples of this category may be seen in the scenic displays of unexcelled grandeur afforded by our far West. Not to these, but to a more commonplace phenomenon, I will now direct the attention of the reader, inasmuch as it is, mechanically speaking, related to and will serve to elucidate the subject under consideration. I have reference to a heap of particles of more or less uniform size, arranging themselves under the influence of the pull or gravity of the earth, with the provision that their magnitude should be very small relative to that of the whole heap. Thus, a grain or gravel heap is an excellent example of the phenomenon I refer to, and it is a very remarkable circumstance that different heaps have the same slope, provided the character of the material and the support upon which they rest remain the same. The slope (the inclination of the sides of the heap with the horizon) is dependent upon the magnitude and shape of the particles, and also upon the nature of the support; the whole sys-