How & A Kelly PREFACE. THE Society for the Promotion of Useful Arts have thought it proper to denominate the present 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 incorporation by that name having expired, a new one was obtained reviving its corporate powers under the present title. Several years have intervened between 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 following sheets were read before the Society at its two last sessions-many important essays communicat |