396 APPENDIX ON THE 



Fig. 364. 



Let fig. 364 represent the primary rhomboid of 

 carbonate of lime. The plane /', fig. 363, is known 

 to result from a decrement by 1 row on the superior 

 edges of that rhomboid. The lines i /, I m, would 

 therefore represent the intersections of the plane 

 /' with the primary planes, the points /, and m, being 

 the middle of the edges df> and//. 



From the middle of the edge d $, draw h b, hf, 

 and the triangle b h f would represent the position 

 on the primary form, of the plane e, fig. 363. 



The planes /' and e are thus observed to intersect 

 each other at the points c and w, and consequently 

 the line cw, would correspond with the common edge 

 of the planes /, and e, if that edge were visible in 

 fig. 363. 



The first parallelism observed by Mr. Monteiro 

 was between the line of intersection of the planes 

 o' and /. and the striae on the plane /. The plane o' on 

 some of the crystals he examined, was so much broader 

 than the plane o, as to exhibit this parallelism dis- 

 tinctly. 



But as the striae are parallel to an edge of the pri- 

 mary form, the edge at which the plane o 1 intersects 

 the plane /, must be parallel to an edge of the pri- 

 mary form, and evidently to the edge a b of fig. 64. 



The second parallelism observed was between those 



