154 -^ Attempt to arrange the 



combination of this law with another not yet determined, 



making the prifm fixteen-lided : fig. 6 a is the plan. 



Third Lazu of Tiecrtment B' D 'B. 



I 



Fig. 7 fliews it incomplete. The plan is fliewn, fig. 23 a, 

 including the dotted lines. Fig. 8, the completion of this 

 law : 8 rt; is the plan. Fig. 32 is an irregular formation^ by 

 this law taking place unequally : 33 a, (without the portion 

 exprefled by the dotted lines,) is the plan. The plans of twn 

 other unequal accumulations, which diiguife the pyramid, 

 are fliewn fig. 7 a, 7 ^. Fig. 21, the fame as fig. 8, become 

 euneiform: 21 a, the plan. 



Fourth Laiv of Decrement A. 

 I 



^ Fig. 9 fhews the combination with the firfl: law: fig. 10, the 

 fame with the third law, incomplete: fig. 11, the laft com- 

 pleted: fig. 12, the combination with the firft and fecond 

 laws : this, and the combination with the firft law only, are 

 in general peculiar toBohemian and Saxon ores; the Englifli 

 ores exhibit bvit few examples of them. I have an Englifh 

 cryftal fimilar to fig. 9, and it is the only one I have feen. 

 Fig. 13, the combination with the fecoud and third law : 



fig. i^a is the plan. 



I 

 Fifth Laiv of Decrement ^E* D. 



Fie;. 14, the firft indication of this law, in combination 

 with the third law, incomplete. Fig. 15, this law farther 

 extended in the fame combination : 15 a, the plan. Fig. 16, 

 a further extenfion, but llill incomplete : fig. 16 a, the plan. 

 Fig. 17, the completion of this decrement: fig. 17/', the plan, 

 Fig. 18, the combination of this law, when arrived at the 

 ftagc {hewn in fig. 16, with the third law. Compare fig. 15 

 and 18. Fig. 19 and 20 are the fame as fig. 16, with fome 

 irregularity in the formation. 



Thefe five laws of decrement embrace all the varieties of 

 facets I have yet obfcrved (except thofe mentioned when 

 fpeaking of fig. 6)3 and by combination; in different ftages 



of 



