250 THE BOOK OF THE LANDED ESTATE. 



blocks from five to twenty feet cube. The colour of this stone is a 

 whitish grey. The following are the constituents of the Craigleith 



stoue : 



Silica, . ..'... .:': ' 95 - 725 



Carbonate of lime, 1.065 



Iron alumina, 2.150 



Water and loss, . . . i . 1-060 



100.000 



The average weight per cubic foot is about one hundred and forty- 

 two Ib. 



We have many examples in this country of the durability of sandstone 

 in buildings. In Yorkshire we have the example of Eivaulx Abbey, 

 which was built in the twelfth century of sandstone found in its vicinity, 

 and the stones are in fine preservation, even showing the original chisel- 

 markings. 



3. Limestones. Limestones are found over many parts of Great 

 Britain in different forms. They are of very great importance in build- 

 ing, being very durable, easily worked, and altogether they much surpass 

 the sandstones as a building material. They are chiefly composed of car- 

 bonate of lime, mixed up with some metallic oxides. They are sometimes 

 found in a pure state, and then they are of a white colour. As a cement 

 for uniting stones they are well known. We have many examples of 

 the durability of the limestone in buildings. Byland Abbey, oii^Major 

 Stapylton's estate, Wass, was erected in the twelfth century. The inner 

 walls were built of a silicious grit, and the outer walls of a compact 

 oolite, got from the Wass quarries about half a mile distant. The front 

 of the building was built of the oolite, and is in very good condition, 

 and the original chisel-markings are still entire. 



St Paul's Cathedral, London, was built of oolite from Portland in 1700, 

 and the markings on the stone are still very distinct. 



Marble is usually taken as a limestone, and the term is applied to 

 those limestones which take a high polish. There are different kinds 

 of marbles, but the difference chiefly lies in the colour of the stone. 

 Some of the best are bird's-eye, conglomerate, and veined. These are much 

 used now in the erection of chimney-pieces. 



It is not always easy to find out the quality of a stone by its appear- 

 ance, but there are things to be seen outwardly which should tend to 

 condemn the stone for building purposes such as cavities and cracks, 

 and an over-abundance of iron in the stone. These are defects which 

 will cause the stone to be coarse-grained and weak. The chief points in 

 selecting good stone is to find them of compact texture, fine-grained, and 

 of a dark colour. 



