Minerals and Fossils in the Gravel at Stairway. 349 



Art. IX. A Synoptical Table of some of the Mineral Substances, 

 and of the Organic Remains, found in the Gravel at Stanivay, 

 Essex, and the neighbouring Localities within a Radius of Fifteen 

 Miles. By John Brown, Esq. 



I submit a list of some of the minerals and organic remains 

 which I have found in searching the gravel in this and the 

 adjoining parishes, within a radius of about fifteen miles from 

 my residence [Stan way, Essex]. Professor Sedgwick has ob- 

 served to the members of the Geological Society, that " the 

 study of diluvial gravel is not only one of great interest, but 

 peculiar difficulty, and of nice discrimination." Still I submit 

 this list with that confidence as to its accuracy which a love 

 of truth and science dictates. 



Much the largest proportion of mineral matters which 

 composes our gravel consists of flints from the chalk, in a 

 broken state. The specimens of the primary and trap rocks, 

 with all the conglomerates or breccias, except No. 6. and its 

 variety, are found in the form of boulders or pebbles mixed 

 up in the mass. No. 6. and the variety of it are found in 

 large irregular masses, are from 3 ft. to 6 ft. in length, occur 

 near the surface, apparently in situ, and are of a different 

 structure from the former breccias. This difference I have 

 endeavoured to particularise in the list. The whole of this 

 debris I have stated to be about 35 ft. in thickness upon an 

 average, within the specified range, and it is highly coloured by 

 the oxide of iron. I need scarcely repeat what I have stated 

 in VII. 438., that the substratum is London clay. In the 

 accompanying paper I have given the particulars. 



Primary llocks. — Granite : in boulders the size of the fist. 

 Several varieties of granite. — 1. Gneiss : in boulders, one the 

 size of the head. — 2. Mica schist : in boulders, one the size of 

 the head. — 3. Grauwacke : in boulders, one the size of the 

 head. — 4. Quartz: in boulders, milk-white, and highly crys- 

 talline, from the size of the head to that of marbles ; and iden- 

 tical with that variety which I have seen in large blocks, 

 scattered over that flank of Snowdon which we descend into 

 the Pass of Llanberris. — 5. Quartz : in granular and crystal- 

 line boulders, like that variety called Druid sandstone ; scat- 

 tered in blocks over the Wiltshire Downs, &c. 



Trap or overlying Rocks. — 1. Hornblende rock : boulders 

 the size of the fist. — 2. Hornblende schist : boulders the size 

 of the fist. — 3. Porphyry : a compact felspar base or matrix, 

 with crystals of felspar and quartz. — 4. Porphyry : with a clay 

 base, with hollow irregular cavities left by the decomposed 

 minerals. — 5. Porphyry : a paste of compact felspar, red 



