. Dental metallurgy, for the use of dental students and practitioners. impossible to recognize them, but by careful study they canbe simplified and referred to one of six systems. To be ableto classify and compare the forms of crystals we must havesome simple mode of expressing the relative positions andinclinations of their planes. This is accomplished by referringthem to systems of axes, according to the method of analyticalgeometry. The position of any crystal plane is thus fixedby and expressed in the relative lengths of its intercepts inthe axes to which it is referred. The axes to which
. Dental metallurgy, for the use of dental students and practitioners. impossible to recognize them, but by careful study they canbe simplified and referred to one of six systems. To be ableto classify and compare the forms of crystals we must havesome simple mode of expressing the relative positions andinclinations of their planes. This is accomplished by referringthem to systems of axes, according to the method of analyticalgeometry. The position of any crystal plane is thus fixedby and expressed in the relative lengths of its intercepts inthe axes to which it is referred. The axes to which the planesof a crystal are referred, called the crystal! ographic axes,may be of equal or unequal length, and may intersect ateither oblique or right angles. The six crystal systems are: 1. The Isomeiric or Regular System.—All the forms refer-able to this system have three axes (imaginary lines passingthrough the solid angles of the octahedron) of equal length,intersecting at right angles. Examples: Regular octahedron, hexahedron (cube) rhom-bic dodecahedron, Fig. 4.—Rhombicdodecahedron. Fig. 5.—Tetra-hexahedron. Fig. 6.—Trisoc-tahedron. CRYSTALLIZATION 55 2. The Tetragonal or Quadratic System.—All forms refer-able to three axes at right angles to each other, two of equallength, the third or principal one having a variable length. Examples: Tetragonal pyramids, tetragonal prisms. Fig. 7
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherphila, bookyear1917
