An improved method of uniting or locking stones together in building light-houses, and for other like purposes, by which the necessity of using mortar is entirely superseded, has been invented by John P. Avery, of Stoning-ton, Ct,, who has taken measures to secure a patent. The method consists in dovetailing together the sides of the stones used for the foundation, and joining them again in a similar manner with others, so that it is impossi-sible to separate them without first breaking the stones in pieces. In order to unite them more firmly, a bolt or key is employed tor pressing the dovetails firmly in their corresponding slots, or pieces ot stone or other material may be employed for this purpose, and the crevices filled up with mortar.