VI PIIEFACK. 



the crystallographic department of the work, as it 

 requires. The formulas which in the German are 

 given in the Preface, are inserted in this translation 

 in their proper place, but without changing the num- 

 bers and distribution of the paragraphs. The names 

 and denominations also remain ; in the characters 

 alone the necessary changes are made, the expression 

 Prismatic in a more general signification being 

 employed as including the prismatic, hemi-prisma- 

 tic, and tetarto-prismatic forms. In regard to such 

 hemi-prismatic forms as have their axis inclined 

 to the base, it should be observed, that the angles 

 of horizontal prisms indicated, are those which the 

 face of the prism includes with the inclined axis, 

 like BAM and B'AM, Vol. I. Fig. 41. 



Those simple forms which have been observed in 

 nature, are noted with an asterisk. For these, and 

 also for each of the combinations, some locality is 

 mentioned in which they have been discovered. In 

 a few instances another variety is substituted in the 

 translation for one in the original, when a certain lo- 

 cality could be obtained for an uncertain one, by a 

 comparison with the specimens in the cabinet of Mr 

 ALLAN. 



The letters inclosed and printed in italics refer 

 to the figures, or to the works of HAUY, sometimes 

 also to particular papers, and in this case the title 

 of the latter has been mentioned. Some of the 



