Geological Poems. 

 To make Amygdaloid. 



fit 



w 



in vvbich bladder-shaped holes may be e\ei\ where seen ; 

 Choose a part where these holes are decidedly void all. 

 Pour SiJex in these, to form Agates spheroidal. 

 And the mass in a trice will be Amygdaloidai. 



To make a good Breccia with a Calcareous Cement. 



Break your rocks in sharp fragments, preserving the angles; 

 Of Mica or Quartz you may add a iitw spangles : 

 Then let your white batter be welt filtered through, 

 Till the parts stick as firm as if fastened by glue- 



i 



To make a coarser Breccia. 



For a Breccia more course you m^y vary your matter ; 

 Pound Clay, Quartz, and Iron-stone, moisten'd with water : 

 Pour these on your fragments, and then wait awhile, 



llll the Ovvf! c^f lrr\n ic vt^A nc a tilo^. 



2 Wacke. See Primer, p. 24 Wacke is generally greenish, and rather 

 unctuous to the touch. This rock muat not be confounded with Grey- 

 Wacce. 



3 The geological Neophyte who attempts to make aggregated rooks from 

 the above approved receipts, should attend to the following directions : — 

 Granite rocks must be compospd of crystalline grams of two or more differ- 

 ent species of minerals closely united without any '^ement— Porphyry, of a 

 base or paste containing imbedded crystals (generally of felspar) — Pudding- 

 stone, of rounded stones plentifully imbedded m a siliceous pa?te — Amygda- 

 loid, of basalt or wacke inclosing nodules of agate or chalcedony — Breccia, 

 of angular fragments of any kind of rock, united by a cement. When large 

 I'ouuded pieces mixed witli fragments are held together by a cement, it i« 

 generally called a coarse conglomerate. 



F 



Vol. V....No. II. 37 



