4S2 



bourhood of Harwich, separated from each other by about 20 feet 

 of clay : and the author mentions that in sinking wells in the town, 

 the chalk has been found at the depth of sixty feet. 



Iron pyrites, occur in great abundance at the foot of the cliffs, 

 and lignite, but sparingly. Fossils are said to be procured chiefly 

 from the cement stone, and a species of Venus to be the most 

 abundant. 



The author next gives a description of the cement stone; the 

 history of its first discovery by the late Rev. Dr. Parker in the year 

 1796; a list of the localities where it is found in the greatest abund- 

 ance; then points out the difference between the cement stone of 

 Harwich and Sheppey, and lastly, advances an opinion on the pro- 

 bable period at which the supply will fail. 



"A Memoir on the Valley of the River Medway and the adjacent 

 Country," by R. Dadd, Esq., and communicated by James Mitchell, 

 Esq., F.G.S., was then read. 



The country described by the author lies in the immediate vicinity 

 of Chatham and Rochester, and is characterized by the passage of 

 the river Medway through a narrow, winding gorge bounded by 

 chalk hills. It exhibits six different deposits, viz. — 



1. Lower chalk. 



2. Upper chalk. 



3. Plastic clay. 



4. London clay. 



5. Diluvium. 



6. Alluvium. 



1. On the right bank of the Medway the lower chalk is very little 

 exposed, appearing principally at Burham, where it is extensively 

 quarried, in the form of low downs covered in many places by dilu- 

 vium. On the left bank it is much more extensive, forming higher 

 and bolder hills, and reaching from the entrance of the gorge to 

 Whornes Place, with a breadth varying from a mile to half a mile. 

 Its fossils are abundant, but not various, being chiefly Ammonites, 

 Terebratulae, Inocerami, Pectens, and remains of Fishes and Saurians. 



2. The upper or flinty chalk is extensive on both sides of the 

 river, forms most of the high land of the district, and is the basis on 

 which the newer deposits rest. Into these strata all the deep wells 

 penetrate. In its mineralogical and fossil characters it is similar to 

 the upper chalk beds of other localities. Its surface is hollowed 

 and uneven, and is often covered, even at considerable elevations, 

 with patches of diluvial matter. 



3. The plastic clay and its accompanying sands appear, at a for- 

 mer period, to have extended over the whole district; for their re- 

 mains are found in every valley, and on every hill patches of it 

 remain undisturbed by the phenomena which attended their eleva- 

 tion. This formation extends from Cuxton valley through Strood 

 to Frindsbury Hill ; as also from Whitewall Creek over and be- 

 hind Barrow Hill, through Upnor, along the banks of the river to 

 near Cockham Wood Fort. An instructive section has been formed 



