Abstract: This invention relates to lawn spreader markers generally, and more specifically to an intermittent manually controlled marking apparatus which delineates the area covered by the spreader hopper opening and which utilizes foam as the marking material.

Abstract: A solar energy conversion unit having a collector forming a focal area in which is disposed a core assembly including a governor arranged for varying the surface area of fluid carrying tubes partly forming the core assembly that is exposed to solar radiation so as to maintain a desired fluid pressure within the conversion unit. At such time as the solar radiation impinging the collector becomes substantially less than that necessary to maintain suitable pressure in the fluid system of the unit, an auxiliary heater provided as part of the core assembly can be employed to supplement or replace the solar radiation.