Elements of Crystallography: After the Method of HaŁy; With, Or Without Series of Geometrical Models, Both Solid and Dissected; Exhibiting the Forms of Crystals, Their Geometrical Structure, Dissections, and General Laws ...

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Longman, Hurst, Rees, Orme, and Brown, 1813 - Crystallography - 396 pages
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Page 34 - ... till it crystallizes on cooling. Alter the position of every crystal, once at least every day, with a glass rod, that all the faces may be alternately exposed to the action of the liquid ; for the face on which the crystal rests never receives any increase.
Page 34 - The salt to be crystallized is to be dissolved in water, and evaporated to such a consistency that it shall crystallize on cooling. Set it by, and when quite cold pour the liquid part off the mass of crystals at the bottom, and put it into a flat-bottomed vessel.
Page 35 - ... in solution becomes so much diminished, that the liquid begins to act upon the crystal and redissolve it. This action is first perceptible on the angles and edges of the crystal. They become blunted, and gradually lose their shape altogether. Whenever this begins to be perceived, the liquid must be poured off, and a portion of new liquid put in its place; otherwise the crystal is infallibly destroyed. Mr. Leblanc has observed, that this singular change...
Page 98 - ... attract the third particle more strongly than the tetrahedron ; that is, it will have a greater affinity for it than the tetrahedron. But if the particles of bodies differ from each other in figure, they may differ also in density and in size : and this must also alter the absolute force of affinity, even when the distances and the figure of the attracting particles are the same. The first of these two circumstances, indeed, may be considered as a difference in th...
Page 51 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees ; each degree into 60 equal parts, called minutes ; and each minute into 60 equal parts, called seconds.
Page 67 - A rhomboid is that which has its opposite sides equal to one another, but all its sides are not equal, nor its angles right angles.
Page 319 - If the percolation of water containing calcareous particles is too rapid to allow time for the formation of a stalactite, the earthy matter is deposited from it after it has fallen from the roof upon the floor of the cavern; and in this case the deposition is called STALAGMITE : the substance deposited is the same as in the case of stalactite.
Page 220 - ... nucleus, undergoing decrements subjected to certain laws, upon which the forms of these crystals depend. But this is only a conception adopted in order to make us more easily perceive the mutual relations of the form in question. Properly speaking, a crystal is only a regular group of similar molecules. It does not commence by a nucleus of a size proportioned to the volume which it ought to acquire, or, what comes to the same thing, by a nucleus equal to that which we extract by the aid of mechanical...
Page 254 - ... a ray of light passes obliquely from one medium into another of a different density, it is refracted, or turned out of its former course.
Page 56 - ... angles is called a right angle; and the straight line which stands on the other is called a perpendicular to it. XL An obtuse angle is that which is greater than a right angle. XII. An acute angle is that which is less than a right angle. XIII. " A term or boundary is the extremity of any thing.

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