M. Liandiere, a locksmith of Paris, has contrived a new form of iron plate for floors, roofs, bridges, 'c., which promises to be hereafter generally employed for such purposes as neither keys nor bolts are required for joining, and the plates can be put up very easily, in a'very short time. The advantages are less manual labor, perfect solidity, less space an,d less thickness in the flooring, no tear of fire, 'c. 1852 SCIENTIFIC AMERICAN, INC