A Familiar Introduction to Crystallography: Including an Explanation of the Principle and Use of the GoniometerW. Phillips, 1823 - 508 pages |
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Common terms and phrases
Abbé Haüy Amphibole axis belonging to class Cerium class d Class f classes of primary Copper crystallised cube decre decrement producing doubly oblique prism edges or angles edges replaced Epidote equal fibrous figure goniometer hedron hexagonal prism Intermediary decrements intersect lateral edges lateral planes lateral solid angles law of decrement mixed decrements modifying planes molecules oblique diagonal oblique rhombic prism oxide parallelopiped perpendicular plane angles planes belonging primary edges primary form primary planes produce the planes Pyroxene Quartz ratio regular octahedron regular tetrahedron replaced by single rhombic base rhombic dodecahedron rhomboid right rectangular prism right rhombic prism right square prism row of molecules Scapolite secondary crystal secondary forms secondary planes shewn siliceous Simple and mixed simple or mixed single planes solid angles replaced square base square prism sulphate sulphuret tables of modifications tang tangent planes terminal edges terminal plane Terminal solid angles unit of comparison
Popular passages
Page 31 - ... edge, /, parallel to the window, the side to which the wax is attached being uppermost, and press the end of the wax against the crystal...
Page 32 - Now turn the graduated circle, by means of the handle, b, until the image of the bar, reflected from the second plane, is also observed to coincide with the same line below. In this state of the instrument the vernier at c will indicate the degrees and minutes at which the two planes are inclined to each other. " The accuracy of the measurements taken with this instrument will depend upon the precision with which the image of the bar, reflected successively from both planes, is made to appear to...
Page 32 - ... pin laterally either towards or from the instrument, in order to make the image of the same bar reflected from the second plane coincide with the same line below. " Having assured yourself, by looking repeatedly at both planes, that the image of the horizontal bar reflected successively from each, coincides with the same line below, the crystal may be considered as adjusted for measurement. Let the 180°...
Page 52 - ... reception than the former theory possessed, I cannot avoid observing that the whole theory of molecules and decrements is to be regarded as little else than a series of symbolic characters, by whose assistance we are enabled to investigate and to demonstrate with greater facility the relations between the primary and secondary forms of crystals. And under this view of the subject, we ought to divest our notions of molecules and decrements, of that absolute reality, which the manner in which it...
Page 29 - Fig. 7. the planes a and b incline to each other. For if the line og be extended in the direction oi, as in fig. 7, it is obvious that the lines, oe, oi, which are perpendicular to the common edge of the planes, a and 6, would intercept exactly 120° of the circle.
Page 447 - Upon examining their optical structure, I find that they have two axes of double refraction, the principal one of which is coincident with the axis of the rhomb. The sulphato-tri-carbonate, therefore, cannot have the acute rhomboid for its primitive form, but must belong to the Prismatic System ofMohs.
Page 30 - The graduated circular plate should stand perpendicularly from the window, the pin x being horizontal, not in the direction of the axis, as it is usually figured, but with the slit end nearest to the eye. " Place the crystal which is to be measured on the table, resting on one of the two planes whose inclination is required, and with the edge at which those planes meet, nearest and parallel to the window. " Attach a portion of wax, about the size of d, to one side of a small brass plate, e, fig.
Page 32 - ... on its axis, to bring the reflected image of the bar of the window to coincide accurately with the line below, now move the lower end of the pin laterally, either towards or from the instrument, in order to make the image of the same bar, reflected from the second plane, coincide with the same line below. " Having ascertained by repeatedly looking at, and adjusting both planes, that the image of the horizontal bar...
Page 447 - Oth volume of the same Journal, p. 183, relative to the crystalline form of the sulphato-tri-carbonate of lead, furnishes an additional motive to believe that the connection between the optical characters of minerals, and their crystalline forms, is not yet sufficiently understood. Dr. Brewster admits what I believe is not liable to question, that " the crystals of this substance are
Page 2 - ... inclosed by the circular line is called the circle (fig. 38). In its relation to this, the circular line is called the circumference or periphery. A portion of the circular line is called an arc, eg abc (fig. 39). The size of an arc with reference to the whole circumference is measured by degrees. Every circle is divided into 360 equal parts, which are called degrees ; each degree contains 60 minutes, and each minute 60 seconds. A straight line, drawn from the centre of a circle to its circumference,...