PREFACE. IX 



kind and friendly assistance which I have received 

 from Mr. Jeffreys, Mr. Hincks, Mr. Philip Carpen- 

 ter, Mr. D. Cooper, Mr. Carter, and especially from 

 Mr. Thompson of Belfast, and Mr. Alder of New- 

 castle, who have kindly sent me specimens for com- 

 parison and figuring. Some apology is, perhaps, clue 

 to those who have been expecting the new edition of 

 the work which has been so long advertised :. this has 

 partly been occasioned by the delay in the comple- 

 tion of the plates, and partly by numerous engage- 

 ments, which have only allowed me to pay attention 

 to the subject at leisure moments, when not occupied 

 by my official duties. 



Eliot Vale, Blackheath, 

 Feb. 12. 1840. 



