29G 
GILLIGAX : THE LOWER PERMIAN AT ASHFIELD, ETC. 
Appendix, 
chemical composition of the beds, 
by m. odlixg, m.a.. b.sc. (oxon.), f.g.s. 
About 40 grams from each bed were crushed up and well mixed 
so that a fair sample might be obtained. In the case of the marls 
shewing banding of gi'ey and red the specimen crushed was somewhat 
larger and contained both, so tliat an average sample could thus be 
obtained. 
Since it had been found in the case of Permian marls recently 
examined from other districts that the insoluble residue left after 
dissolving in hydrochloric acid consisted largely of gypsum, it is re- 
markable to find that these marls are practically free from sulphates. 
In the cases of specimens yielding a high percentage of insoluble residue 
a portion was fused up and tested for sulphates, but in most cases the 
amount found was not considered sufficient to justify the expenditure 
of time necessary for a complete examination ; in the cases in which 
this was done it has been neglected in the tables, as when estimated as 
CaS04 2H2O it never amounted to over 0-3 per cent, of the rock. 
In the first table (p. 294) the Loss on Ignition " would appear 
to be chiefly due to the water from hydrated silicates ; the Insoluble 
Residue contains also all the silica, the Fcg O3, " etc., would 
contain small traces of MnO^ and other oxides of this group, whilst 
the AI2O3, etc., might contain traces of TiOg. The calcium and 
magnesium have been calculated as carbonates and entered as 
dolomite and calcite as being the most probable state in which they 
occu:-. 
In the last two columns is shewn the relative percentage of calcium 
to magnesium carbonate, which in a pure dolomite should be CaCOg, 
54-27 per cent. ; MgCOg, 45-73 per cent. 
Assuming that all the alumina existed in the form of kaolin and 
deducting the necessary amount of silica and water to satisfy this 
alumina from the " Insoluble Residue '"' and " Loss on Ignition " res- 
