69 



to the olive, arc now picked up under the clifiFg lietweon Whit 

 stable and Old Haven Gap, in which the vegetable matter has 

 been transformed into pyrits. It is commercially used for making 

 protosiilphate of iron and oil of vitriol. On the coast of 

 Sheppey I have picked up large pieces of fossil wood bored 

 through by the Toredina personata, the Eocene representative 

 of the present Teredo or ship-worm. The wood has been 

 changed into a silicate of lime and alumina. The bore holes 

 made by the mollusc are lined with a calcareous cement, 

 a means which the creature adopted for making his habi- 

 tation comfortable, similar to that wliich wg have made 

 use of in the plaster that covers the ^^-alls and ceilings of 

 GUI' rooms. Not that man is merely a copyist, but because 

 the one Creator has given reason to man and the power 

 of adaptation to lower beings, so that a similar requirement is 

 attained by like means, in the same manner that the touch of a 

 great artist is observable through many anil various works and 

 his style transmitted to his jiupils thouf?h their productions may 

 be inferior. The nodular masses of silicate of lime and alumina 

 so abundant in this formation, remind one of the flints in the 

 chalk. From the pecidiar reticTilated planes of calc spar that 

 pass through them, thej^ have received the name of Septarieoe. 

 In one of these nodides I obtained from the Isle of Shej)pey, I 

 found some very curious foliated crystals of siUphate of baytes, 

 and in another from the Bognor beds which I was so fortunate 

 as to break oi)en, was disclosed the shell of a Pectunculus 

 brevirostrum containing four small oysters. (See anuuol report 

 for 1877, page 44.) The large mollusc must have arrived at 

 maturity and died ; the gaping shells were then taken possession 

 of by four lively youug oysters, who there settled down for life 

 and that but a brief one, for they were like the young princes in 

 the Tower, smothered in their bed, and for countless ages have 

 been enclosed in a beautiful little coffin. Tlie London Clay of 

 the Isle of Sheppey is covered in some places by the Bagshot 

 sands, thus enabling the geologist to determine the thickness of 

 the clay, without wliich it would be impossible to make out how 

 much had been removed by denudation. It is estimated at four 

 hundred and fifty feet. Leaving out the Old Ilaven beds which 

 vary fi-om a few inches to thirty feet, and taking the Wool- 

 wich beds at fifty feet, and the Thanet Sauds at a hundred, 

 we have a thickness amomiting to six hundred feet of tertiary 

 beds. The age of the great reptiles which we glanced at in the 

 Wealden draws to a close in the cretaceous period and the reptile 

 is no longer the leading feature of the animal creation when we 

 pass from the secondary to the tertiary rocks. A few and scat- 

 tered remains in the London Clay of the Isle of Sheppej' of tlu'ee 

 specimens of Pach3-dermata (mentioned in Lyell'.? Elements, 



