554 ON THE STRATA OF LINCOLN. 



3. Called the Blue bed, a hard limestone, wherein spar and 



crystalline cockles are found. 



4. Knobbly or Boss rubble ; — contains casts of shells. 



A layer of marie lies underneath. 



5. The Shell bed ; — stone cockles in great variety are found 



in this bed. 



A layer of marie lies underneath. 



6. The Blue Limestone bed ; — contains the Mactra, a kind 



of muscle. 



7. Three beds of the Grey Limestone, each bed intercepted 



with marie ; — oysters, Murex, the lobster- tailed nautilus 

 or miller's thumb, and the Chiton, [? — Ed.] are found 

 in these beds. 



8. Three beds of fractured limestone, each bed intercepted 



with a layer of marie, 



9. A strong limestone bed called the Roof bed, under which 

 the ancient builders excavated or rather mined, for supe- 

 rior stone for building the Cathedral, which may account 

 for the numerous caverns and subterraneous places to a 

 great extent. A very large portion of the upper part of 

 Lincoln, and nearly the whole of Eastgate, is thus un- 

 dermined. 



10. Three thin knobbly beds intercepted with marie. 



11. The Oolite Freestone bed; — calc spar occurs here in 

 rhombic and prismatic crystals. Large Ammonites, and 

 the Teredo or Lapis Syringoides, and fossil wood, are 

 found in this bed. 



12. The Silver bed ; — it abounds with cornbrash and Archi- 



medes shells ; it is allied to the forest-marble, and when 

 faced, is used for chimney-pieces and for floors of pas- 

 sages ; it decomposes oily matters, and is a durable stone 

 for buildings in dry situations ; — prismatic and rhomboid 

 calc spar is found in this bed. 



13. A bed of good building stone, superior to the silver bed, 



about sixteen inches in thickness ; — this bed abounds in 

 some parts with cornbrash and Archimedes shells, the 

 same as the silver bed ; in other parts it is free from 

 cornbrash. Between the fissures in this bed, the agaric 

 mineral occurs in delicate opaque crystals. The dag- 

 ger shells, razor-sheath, and various other shells, are 

 found in this bed. 



14. Two beds of good stone, with oolite disseminated, useful 

 for foundations and building purposes. In the first bed 

 fossilized branches of trees sometimes occur, lying hori- 

 zontally. Prismatic calc spar in bold crystals occurs in 

 this bed. 



