INTRODUCTION. 
The general arrangement and preparation of the work has been confided 
to Lieutenant Larcom, and I cannot speak too highly of the indefatigable 
exertions he has made to render it as correct and as perfect as possible; at his 
request I also acknowledge the assistance he has derived from Mr. George 
Downes. And in closing these introductory observations, I have to express my 
approbation of the zealous exertions which all those employed have made in their 
various departments to contribute their aid wherever it has been requisite. 
THOMAS COLBY, 
Lieutenant Colonel Royal Engineers. 
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