PREFACE. 
The Society for the Promotion of Useful 
Arts have thought it proper to denominate the pre¬ 
sent volume the third of their transactions—Their 
first was published under the title of Transactions 
of the Society for the Promotion of Agriculture , 
Arts and Manufactures; but the act of incorpora¬ 
tion by that name having expired, a new one was 
obtained reviving its corporate powers under the 
present title. Several years have intervened be¬ 
tween the appearance of this volume and the second 
—The Society hope in future to publish a half 
volume annually. 
Most of the papers to be found in the follow¬ 
ing sheets were read before the Society at its two 
last sessions—many important essays communicat- 
