Abstract: For automatically creating intermittent disturbances in slurry digesters, natural waters and the like, there is provide a device (c) to be immersed below the surface of fluid in the digester, below water level and adjusted to collect generated or supplied gas, the device being pivoted to swing about axis (P) from the collecting position to a gas discharge position and the collecting space being shaped adjacent its mouth so that, as it fills with collected gas, the line of action of the buoyant upthrust on the device moves relatively to the swinging axis until the upthrust causes swinging of the device to allow the gas to discharge as a massive bubble, and after discharge to return to a collecting attitude.

Abstract: To improve the performance of four-stroke internal combustion engines, the piston P of each cylinder C is connected by a connection rod to an intermediate point of a floating link, which point is constrained, for instance by a tracking arm, to travel substantially rectilinearly, and the ends of the floating link are joined by connection rods to primary and secondary crank shafts which are coupled together to rotate at a selected ratio of different rotational speeds, the ratio best being 2:1. The arrangement is such as to give a longer power stroke than induction stroke. Further the cylinder may be provided both with a normal valve-controlled exhaust port and with exhaust ports which are only uncovered at the end of the power stroke.