340 
Tin; CRETACEOUS ROCKS OF BRITAIN. 
The following are analyses of two specimens from the upper 
part of the Lower Chalk in Wilts and Dorset. Our thanks are 
due to Professor J. B. Harrison, of Georgetown, British Guiana, for 
making these analyses from samples sent over to him, and they 
exhibit the mineralogical composition of the material more com¬ 
pletely than any others except Mr. Berry’s, because his method of 
analysis secured complete separation of the several siliceous ingre¬ 
dients. Under the head of clay is included the combined silica 
existing in the form of silicates, with the associated alumina, 
peroxide of iron, oxide of manganese alkalis and magnesia. 
No. 1 is a greyish chalk taken from about 20 feet below the Mel- 
bourn Bock in a quarry on Brimsdown, south-west of Warminster 
No. 2 is from a quarry at Belchalwell, Dorset, and from about 
50 feet below the Melbourn Bock: — 
1. 
2. 
Moisture - 
« - 
- 
- 
•90 
•20 
a s . : 
Quartz 
- 
- 
3*50 
2*20 
Clay (silicates) 
- 
- 
- 
4’95 
6-00 
Colloid silica - 
- 
- 
- 
1 *15 
2*95 
Carbonates of lime and magnesia - 
- 
- 
89*50 
88-65 
100*00 
ioo-oo 
It will be noticed that an appreciable amount of fine quartz sand is found 
in these samples by Professor Harrison, and this agrees with the results of 
Mr. Hill’s chemical researches into the composition of samples from similar 
horizons in these counties (see p. 314). 
Mr. Whitaker places at my disposal the following analyses of 
four samples of grey chalk (from two pits at Hailing), lent by 
Formby’s Cement Works Company, analysed by H. Faija, Novem¬ 
ber, 1883, and communicated by Mr. J. H. Wood (of the Company). 
1 . 
2. 
3. 
4. 
Top 
Bottom 
Top 
Bottom 
Old Grey 
Old Grey 
New Grev 
New Grev 
Pit. 
Pit. 
Pit. 
Pit. 
Moisture. 
The Dried Residue contained : 
8-8 
9*5 
4*5 
9*09 
Carbonate of lime - 
88*3 
89*65 
90*35 
90*04 
Silica. 
6*7 
5*55 
5*75 
6*825 
Alumina, with traces of iron - 
5* 
4-65 
3-65 
2*725 
100 
99*85 
99-75 
99-95 
Amount of quartz-sand 
•15 
•25 
•20 
•175 
The following are two analyses of grey chalks from Kent. The 
first is stated to have been “ a specimen from the base of the Grey 
Chalk at Folkestone,” but it is not stated w r hat bed was taken as 
the base of the “ Grey Chalk,” and as the analysis shows a very 
high proportion of calcium carbonate, it probably came from a 
