iO Mr. W. H. Miller on the Crystal of Bicarbonate of Ammonia. 



in the southern Tyrol, the green-sand in France, and the ter- 

 tiary rock of Verona, are all occasionally distinguished by beds 

 of dolomite, although the formations containing it are frequently 

 far removed from igneous rocks, to the influence of which, 

 any alteration of their original structure could by possibility 

 be due. Nor can it be allowed that the grotesque peaks of 

 the Tyrolese dolomite afford countenance to the above hypo- 

 thesis ; since their irregularity of outline may have been in 

 great measure produced by the vast dislocations which these 

 rocks have undergone subsequent to their deposition. — In an- 

 other memoir I have endeavoured to show* that on the southern 

 flank of the Tyrolese Alps near Bassano, where the secondary 

 and overlying tertiary deposits have been elevated conformably, 

 the serrated outline of those several formations from the newest 

 tertiary conglomerates to the dolomite of the Jura limestone, 

 is exclusively due to the high inclination and verticality of the 

 constituent strata. 



VII. On the Crystalline Form of Bicarbonate of Ammonia. By 

 Mr. W. H. Miller. 



To the Editors of the Philosophical Magazine and Amials. 

 Gentlemen, 

 "tT AVING never seen any correct description of the crystals 

 ■*--'- of bicarbonate of ammonia, and understanding that some 

 attempts to crystallize it for the purpose of measuring the in- 

 clination of its faces were unsuccessful, I am induced to send 

 you the following description and measurements, which, how- 

 ever, vary 15 or 20 minutes in different crystals. 



It cleaves parallel to the lateral planes (M M') of a right 

 rhombic prjsm, which appears to be its primary form. The 

 planes b b, are often wanting, 

 and usually very small: when 

 a and M are nearly equal, the 

 crystals may easily be mis- 

 taken for reffular six-sided 



* Phil. Mag. and Annals of Philosopbv, June 18-29 ; and read before 

 the Geological Society, March 182!<. 



It 



