Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/306

 Mr. Webster discovered the pure alumine; we found however a large loose block containing this substance which filled cavities and veins in a mass of singular structure, composed of irregularly concentric thin layers of gypsum alternating with still thinner laminæ of ochreous iron ore. There were also small crystals of selenite in the same cavities with the alumine. The whole mass had strong marks of stalactitic origin, and was probably introduced into one of the cavities on the surface of the chalk by infiltration from the incumbent beds of marl, which abound in shells and iron pyrites, and contain all the elements from which the alumine, iron, and gypsum might be derived.

In this cliff of the Castle Hill at Newhaven the following section is presented, shewing beds of the plastic clay formation above the chalk.