the Silurian and Cambrian Limestones. 367- 



Carbonate of lime 39"54 



Carbonate of magnesia .... 1*85 



Sesquioxide of iron and alumina. 4*68 



Phosphoric acid 0'16 



Organic matter 0"73 



Insoluble 52-27 



Water 0-53 



99-76 

 Loss 0-24 . 



100-00 



3. Lower Silurian. — Bala limestone, Rhiwlas, Wales. The 

 specimen was fossiliferous and vei-y impure, being more strictly 

 an indurated marl than a limestone. The carbonate of lime 

 present appeared to be disseminated through the mass as crystal- 

 line particles. 



The residue, after dissolving in acids, appeared to be a clay. 

 The specific gravity was found to be 2-78 at 60° F. 



28"84 grs. were examined, and yielded 5-66 grs. carbonic acid 

 as loss; 21-08 insoluble, and 0-94 organic matter; 0-39 sesqui- 

 oxide of iron and alumina with phosphoric acid ; 0-06 phosphate 

 of magnesia from phosphoric acid determination, and 0-53 gr. 

 from the estimation of magnesia. 



The analysis when tabulated will be — 



Carbonate of lime 19-51 



Carbonate of magnesia . . . . 1-04 



Sesquioxide of iron and alumina. 1-21 



Phosphoric acid 0*14 



Organic matter 3-50 



Insoluble 73-13 



98-53 

 Water and loss 1-47 



100-00 



4. Loiver Silurian. — Limestone from Diuover Park near 

 Llandeilo. Specimen very fossiliferous, containing abundance of 

 Ogyrjia Buchii ; it had a compact appearance, and dark bluish- 

 gray colour. The specific gravity was 2-70 at 60° F. 



The analysis was executed upon 23-07 grs., and gave carbonic 

 acid, 18-57 grs. ; insoluble, 4-12 ; organic matter, 0-13 ; sesqui- 

 oxide of iron and alumina with phosphoric acid, 0-32 ; phosphate 

 of magnesia from phosphoric acid determinatioUj 0'21 ; ditto 

 from determination of magnesia, 0-30. 



These results afford the following per-centage composition : — 



