in the Neighbourhood of Ferrybridge, in 1826-1828. 407 



quarries, another layer of limestone rubble more mixed with 

 pebbles from a distance. Sand and pebbles generally over- 

 spread the whole. The most curious circumstance relating to 

 the arrangement of the diluvium is, that the rubbly limestone 

 fragments are so deposited as to have their flat surfaces ob- 

 liquely sloping toward the east, which could only have been 

 occasioned by the continued action of a westerly current. Such 

 a current is indicated by the nature of the sandstone and 

 limestone boulders, which evidently belong to rocks in the 

 western part of the county. 



No. 1. — Alluvium. 



The valley of the Aire is filled in its upper part with a va- 

 riety of substances brought down by the stream and deposited 

 in its flood way. Broken trees, pebbles, sand and clay, are 

 met with in sinking on its banks. Nearer the sea this river 

 flows through a flat country of silt or fine clay deposited by 

 the tide, and protected by banks. The alluvial deposit at 

 Ferrybridge and Knottingley is situated at the point to which 

 the sea formerly flowed, and has probably been produced by 

 land-floods and muddy tides. Its substance is a fine rather 

 tenacious clay or silt, such as commonly subsides from agitated 

 water. 



The excavation for the new canal was continued for some 

 length in this alluvium, and afterwards extended through the 

 Knottingley limestone. When it approached the limestone, 

 the workmen were surprised to find, at the depth of twelve feet, 

 a quantity of hazel branches and roots, with abundance of nuts, 

 some hawstones, green moss, bones, and shells. Their asto- 

 nishment was increased when the hardness of the branches 

 proved that they had become stone. Mr. Richardson collected 

 the most interesting specimens, and presented duplicates to 

 the Yorkshire Philosophical Society. The following is an 

 enumeration of the varieties. 



Shells. — None but freshwater kinds ; as Lymncea putris, 

 Cyclas cornea, Planorbis comens. 



Nuts, in extreme perfection. Most of them were soft when 

 first extracted, but they hardened by exposure. They were 

 generally empty and light. But some few heavy specimens 

 had undergone a singular change: the kernels were con- 

 verted to solid white carbonate of lime, while the brown pel- 

 licle of the kernel remained unaffected, and the shells were 

 not at all petrified. Sometimes crystallized calcareous spar 

 was seen in the space between the pellicle and the inside of 

 the shell. 



Wood, believed to be chiefly hazel roots. Some of it is un- 

 altered in substance, the rest more or less impregnated with 



carbonate 



