Geologists are divided in opinion with respect to this deep-sunk red bed, which certainly is not always continuous (for instance, it was not found at a boring at Harwich), and some incline to the opinion that it belongs to the New Red, others that it is the equivalent of what is styled the Red Chalk. But it is difficult to give a solution at present. It is certain that in the gault formation, or near it, beds of a red colour are occasionally found. Near Dorking the lower greensand is capped by a local bed of bright red clay, eight feet thick. And examples of red clays from the gault of Ringmer in Sussex and Charing in Kent can be seen in the Museum of the Geological Society of London. Whether they have any relation with the Red Chalk proper of England depends upon the position which is given to that formation.
Geologists generally consider the Red Chalk as really equal to the Gault. Many of the fossils certainly are gault species; others no doubt belong to the Lower Chalk; and, therefore, probably it is better to regard it as an intermediate formation between the Lower Chalk and the Lower Greensand, which comes into being when the Gault and Upper Greensand have almost thinned out.
One of the members of our Committee, Mr. Rickard, has been good enough to make me an analysis of the Red Chalk of Speeton and Hunstanton. The Speeton is as follows:—
| Carbonate of lime, with a little alumina | 81.2 |
| Peroxide of iron | 4.3 |
| Silica | 14.5 |
| 100. |
From Hunstanton—
| Carbonate of lime, with a little alumina | 82.3 |
| Peroxide of iron | 6.4 |
| Silica | 11.3 |
| 100. |
The latter of which agrees remarkably well with the colour of the specimen, for the Red Chalk of Hunstanton is brighter than that of Speeton.
Two specimens of the borings of Kentish Town, one a red argillaceous and the other a siliceous mass, gave the following results:—
Argillaceous—