364 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 22, 



Red Bunter, Analysis No. 23, by Dr. Voelcker, contained 

 Sesquioxide of iron 1*84 per cent. 



Grey blotches, Analysis Ko. 24, contained 



Sesquioxide of iron 0*54 per cent. 



The light and dark parts of mottled Cambrian grits, Bayston Hill, 

 near Shrewsbury (fig. 24, Plate XIII.), indicated the following dif- 

 ferences in the percentage of the colouring oxides of iron : — 



Analysis ISTo. 11, Chocolate ground, contained 



Protoxide of iron 1 



Sesquioxide of iron 7'60 [- Metallic iron 5"46. 



Silicate of iron 0-33 J 



Analysis 'No. 12. Light blotches and bands following the joints. 



Protoxide of iron ......... 0-08 1 T.r , ■,-,. . o ic 



c, • • J i> • o f\f\ > Metallic iron 2-lb. 



Sesquioxide 01 iron 3"Uu J 



The variegation resulted therefore from the departiu-e of nearly 

 two-thirds of the oxides of iron from the light portions without the 

 state of combination of the remainder being much affected. 



Of the states of combination, and of the proportions of iron in the 

 light and dark parts of blotched red clays and marls, the following 

 are examples. 



Soft red clay mottled with buff, lying from 20 to 30 yards above 

 the Sulphur-coal, Shropshire Coal-measures, Broseley. 



Analysis 'No. 15, of the red ground, contained 



Protoxide of iron 0'54 "1 



Sesquioxide of iron 11-60 v Metallic iron 8-64. 



Silicates of iron 0-15 J 



Another analysis (No. 35) of the same clay indicated the presence 

 of 7*54 per cent, of sesquioxide of iron, and traces of protoxide. 



Analysis No. 16, of the buff blotches and seams in No. 15, con- 

 tained 



Protoxide of iron 0-90 ^ 



Sesquioxide of iron 4-20 I Metallic iron 4-01. 



Silicates of iron 0*54 J 



A determination of the iron of another example of the buff 

 blotches (No. 16) was made at the laboratory of the Jermyn-Street 

 Museum with the following result : — 



Total iron 



/Soluble l'73l 



[Insoluble 0-( 



I 2-41. 



which was present as 



Sesquioxide of iron 1"81 



Protoxide of iron , soluble 0"60 " 



Oxides of iron insoluble, "I q.oo |-1"48. 



weighed as protoxide... J 



Eed Permian marl, with buff blotches (Severn VaUey Railway, 

 near linley station) : — 



Red marl (Analysis No. 4, Dr. Yoelcker) contained 



Sesquioxide of iron 3*23 



Protoxide of iron r35 



Bisulphide of iron 0'02 



