42 ( ANNUAL ADDRESS, MDCCCLXXIII. 



for the most part, and carbonaceous matter 1,260 grains, 

 or nearly 3 oz. of silica, which when we put it under 

 the microscope we were delighted to find consisted en- 

 tirely of microscopic crystals of six-sided prisms, termi- 

 nated by six-sided pyramids, the usual form of rock 

 crystal. It may be accepted as a fact that in the moun- 

 tain limestone these beautiful crystals are prevalent. Mr. 

 Woodcroft has dissolved many pieces, and has always 

 round them. In the Buxton limestone they occur in 

 larger crystals, and a little worn or corroded, but in that 

 of this locality (except in the hydraulic mountain limestone 

 of Waterhouses, near Leek, in which the silica occurs in 

 an amorphous form,) they are always perfect in form, trans- 

 lucent, and very interesting objects, averaging in measure- 

 ment about the 400th of an inch in length by the 1,000th of 

 an inch in breadth. The smallest are less than 1,000th 

 of an inch long. The crystals obtained from both the 

 Buxton and Caldon limestones are under the microscopes, 

 and this bottle contains the 3oz. of crystals obtained from 

 the 30lbs. of limestone. They are at the disposal of any 

 ladies or gentlemen who may be desirous of having some 

 for microscopic objects. They are as interesting and as 

 beautiful polariscope objects as any I know of, and those 

 who have to their microscopes the accessories for polarized 

 light will derive much pleasure in their examination. The 

 encrinital slabs which seem wholly composed of fossils 

 also contain these crystals. They do not appear to be 

 present in the liassic, oolitic, or Silurian limestones. 



I shall conclude my paper by a short enquiry into the 

 origin of Limestones. How were they formed ? There 

 can be no doubt that the sea owes the limestone it con- 

 tains in solution to its solvent action on rocks containing 

 lime, and to the carbonate of lime brought down into it 



