90 



Count de Bournon on the Laumonite, 



TABLE OF THE MODIFICATIONS OF THE PRIMITIVE CRYSTAL 

 OF THE LAUMONITE. 



Primitive Crystal. A tctrahedral 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 123" 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. 



^b 



An^lesformed 

 by the meeting 

 of the new 

 planes with 

 the side of 

 the prism on 

 which they are 

 inclined. 



Angles form- 

 edbythemeet- 

 ing of the new 

 planes with 

 the sides op- 

 posite to those 

 on which they 

 are inclined. 



136°, 15' . 



144°, 2' . 



eS", 48' . . lOS", 42' 



17 !•, 55' . . 1000,35 



Angles for- 

 med by the 

 meeting of 



the new 

 planes with 

 those of the 

 1st modifi- 

 cation. 



Angles for- 

 med by the 

 meeting of 



the new 

 planes with 

 tliOoeof the 

 2d modifi- 

 cation. 



Angles for- 

 med by the 

 meeting of 



the new 

 planes with 

 those of the 

 ;id modifi- 

 cation. 



Nattire of the 

 Retrogradations. 



Retrogradation 

 by a single row. 



Retrvicrradation 



by 4 rows in 



breadth, and 3 la- 



' jnins in height. , 



147-, 27' 



155*, 14' 



Retrogradation 

 by 5 rows. 



147", 44' 



Retrogr^iilation 

 by 7 rows. 



