The engraving shows an invention designed to remedy this defect in air compressors and pumps, to provide a device which will enable the compressors and pumps to operate with equal pressure on both sides of the delivery valve. The invention consists of an auxiliary valve arranged outside of the cylinder, where it is not subjected to back pressure, and connected with the delivery valve by a hollow valve stem. In the engraving, which is a sectional view, the cylinder of an air compressor is represented, on the end of which there is a ring containing delivery ports, through which the air from the cylinder is forced into a receiver or conducting pipe. This ring is provided with an inner flange or valve seat on which rests the delivery valve. These parts are similar to those seen in some of the air compressors in common use, and with this construction and arrangement one hundred pounds pressure to the square inch in the cylinder is required to open the valve against eighty pounds pressure in the receiver or in the conducting pipes. [Illustration: AUTOMATIC BALANCE ATTACHMENT FOR DELIVERY VALVES OF AIR COMPRESSORS AND WATER PUMPS.] A drum having an open end is connected with the cylinder head by inclined standards, and contains a piston connected with the valve by means of a rod that extends centrally through the cylinder head. On the outer end of this rod is screwed an adjusting nut, by means of which the piston may be adjusted. This rod is bored longitudinally, establishing communication between the compressor cylinder and the drum containing the piston. It will be seen that the upper face of the piston is exposed so as to be subjected to atmospheric pressure only, and when the compressor is in operation a portion of the air in the compressor cylinder passes through the hollow rod into the space beneath the piston, and there exerts sufficient pressure, in combination with the pressure on the inner face of the valve, to open the valve against an equal pressure in the receiver or conducting pipes, so that when the pressure in the cylinder equals the pressure in the receivers the valve is opened and held in place until the piston in the cylinder starts on the return stroke, when the pressure under the piston is immediately relieved through the hollow rod and the main valve closes. The space between the valve and its seat is made as shallow as possible, so that the space may be quickly filled and exhausted. The piston may be adjusted to regulate this space. This invention was recently patented by Messrs. Samuel B. Connor and Henry Dods, of Virginia City, Nevada. * * * * * IMPROVED SAFETY VALVE.