166 REPORTS ON THE STATE OF SCIENCE. 
This is the jasper which occurs in the interstices of the pillowy 
diabase. It will be seen that the analysis is quite unlike that of any 
felsite or rhyolite, unless such a rock had been altered by introduc- 
tion of silica and iron, and of such a phenomenon there is no evidence 
whatever on the ground. ‘The relations, moreover, of the jasper to the 
diabase are quite inconsistent with such a view. 
Llanddwyn, near 312A. 
Dolomitic Limestone. 
Percentage MnO='01 
ae N00, 016 
This is to supplement an analysis made in a former year of 
a limestone associated with the pillowy lavas and jaspers. Jaspers 
occur in these limestones, as well as in the lavas. They frequently 
have a delicate rose colour, and this, it will be seen, is due to sub- 
stitution in the carbonate of a small percentage of rhodochrosite. 
Nos. 548 and 549 have been selected as extreme types of the lime- 
stones of the Carboniferous series, some of which are thick-bedded, light 
coloured, clean, and crystaline; the others thin-bedded, dark coloured, 
earthy, and compact. 
No. 548A. White Limestone. Carboniferous. 
Benllech Cove. 
ig Il 
Residues insoluble in HCl , H))0:32 O41 
BROS We OLS Pi Aig tone sae eye. 0-19 
CaO ©. 3 : ‘ : ; « 55743 55°37 
MgO. 5 : : ; “ = -- 
GO; . : ‘ ‘ ‘ ; . 4416 44-19 
100:08 100°16 
Percentage CaCO, 98:98 98°87 
Very white and crystalline. Its purity is remarkable. Corals are 
often abundant in the limestone of this type. 
No, 549A. Black Limestone. Carboniferous. 
Benllech Sand. 
it aE, 
Residues insoluble in HCl 5 . 22°02 21°66 
Al,O,+ Fe,O,  . ; : : . 0:24 0-49 
CaO F . F : : 22 AlibT 41°61 
MgO m , . ; - Se leo 1:16 
COs ; . ‘ ‘ ; oye} 33°91 
98°73 98°83 
Undetermined = 1:27 117 
Percentage CaCO, = 74°23 74°30 
The insoluble portion has the following composition :— 
BAGS Sh, Wey PRU es wtp ratins er 90:23 
ALOreHs.O1 i Geethe fF be eaeee 9°28 
99°95 99°51 
