HAMMER, a well-known tool uſed by mechanics, conſiſting of an iron head fixed croſswiſe upon a handle of wood. There are ſeveral ſorts of hammers uſed by blackſmiths; as, firſt, the hand-hammer, which is of ſuch weight that it may be wielded or governed with one hand at the anvil; ſecond, the up-hand ſledge, uſed with both hands, and ſeldom lifted above the head; third, the about-ſledge, which is the biggeſt hammer of all, and held by both hands at the fartheſt end of the handle, and being ſwung at arms' length over the head, is made to fall upon the work with as heavy a blow as poſſible. There is alſo another hammer uſed by ſmiths, called a riveting hammer, which is the ſmalleſt of all, and is ſeldom uſed at the forge unleſs upon ſmall work. Carpenters and joiners have likewiſe hammers accommodated to their ſeveral purpoſes.