An improvement on the rotary pump has been lately invented by John Laing, of Brooklyn, N. Y., who has taken measures to secure a patent. In this improved pump the piston is made to work in a recess or slot let into the circular head on the top of the shaft, the circular head being placed eccentric with the bore of the cylinder, which is fashioned of a slightly elliptical form. By this arrangement the length of the piston does not require to be varied, which would ba the case if the bore of the cylinder was made circular. In order that the pump may draw as soon as it is worked, a reservoir or water chamber is placed beside it, with which the supply and feed pipes communicate. The piston, as it rotates, forms a vacuum in the lower part of the cylinder whenthe water rushes in through the supply pipe, which is separated from the discharge pipe by means of the circular head on one side of the cylinder, and the action of the piston bearing against it on the other. The end of the piston, when it passes the orifice of the supply pipe, forces the water around the cylinder into the discharge pipe, and when it has passed this latter, the other end of the piston goes through a similar operation, which is performed alternately by either end as the piston rotates.