Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/102

TABLE OF THE MODIFICATIONS OF THE PRIMITIVE CRYSTAL
OF THE LAUMONITE.

Primitive Crystal. A tetrahedral prism slightly rhomboidal of 92° 30′ and 87° 30′, with rhombic bases inclined on the edges formed by the meeting of the sides of the prism at an angle of 92° 30′, so as to form with them angles of 125° and 55°. The height of the prism is to the edges of the terminal faces in the ratio of 8 to 7.

Retrogradations along the edges of the prism formed by the meeting of its sides at an angle of 92° 30′.
Number of the modifi- cations.	Figure of the crystal	Angles formed by the meeting of the new planes with the side of the prism on which they are inclined	Angles formed by the meeting of the new planes with the sides opposite to those on which they are inclined	Angles formed by the meeting of the new planes with those of the 1st modification.	Angles formed by the meeting of the new planes with those of the 2d modification.	Angles formed by the meeting of the new planes with those of the 3d modification.	Nature of the retrogradations
1st	Primitives Crystal with planes of substitution on the edges of 92° 30′	130°, 15′	136°				Retrogradation by a single row
2d		144°, 2′	128°, 28′	172°, 13′			Retrogradation by 4 rows in breadth, and 3 laminæ in height
3d		168°, 48′	103°, 42′	147°, 27′	155°, 14′		Retrogradation by 5 rows
4th		171°, 55′	100°, 35′	139°, 52′	147°, 44′	176°, 23′	Retrogradation by 7 rows