36 ANNUAL ADDRESS, MDCCCLXXIII. 



system Jurassic, from the Jura mountains, where its 

 limestones are grandly developed, and Oolitic from the 

 peculiarity of some of its limestones being formed of 

 granulated particles of an egg-shaped form, or like the 

 roe of fishes. Bath and Caen stones represent this struc- 

 ture. The thickness and number of beds of limestone 

 in this formation are very considerable. Fossils abound 

 in them, from the great saurian reptiles of Lyme Regis 

 and Barrow, to the beautiful forms of the lily encrinite. 

 Specimens of liassic limestones and fossils lie on the 

 table. The lias limestones are dark-coloured and earthy: 

 they form, when burnt, what is called water lime, which 

 has the property, when made into mortar, of hardening 

 under water. Bath and Caen stone occur in this forma- 

 tion, and are extensively used in carving and internal 

 architectural decoration. They are so soft as to be easily 

 sawn, but harden considerably on exposure. 



From the Jurassic we ascend into the Cretaceous or 

 Chalk formation. This is the uppermost or newest mem- 

 ber of the Secondary system. The appearance of chalk 

 is too well known to need description. It is a limestone 

 like the others, save in appearance. It is divided into 

 chalk without flints, 600 feet in thickness ; chalk with 

 flints, upwards of 1,000 feet thick ; and Maestricht or 

 pisolitic chalk and Faroe beds, 100 feet thick, in which 

 are the extensive and celebrated caverns at Maestricht in 

 Holland. Chalk is most extensively developed in England, 

 and covers more ground than all the other limestones put 

 together. From Flamborough Head, in Yorkshire, it ex- 

 tends to the south-east coast, and as far westward as 

 Sidmouth, being sometimes covered by Tertiary rocks. 

 The fossils are very numerous, seventy species being 

 characteristic of it. When a piece of chalk is carefully 



