Abstract: A method of providing useful work utilizing the difference between higher and lower elevations and an attendant difference in temperature. The method includes the step of providing a working medium comprised of more than one component, the components having different temperature values at which they vaporize and condense. Vapors of the working medium are condensed at the location of the higher elevation, and are directed under the force of gravity to means at a lower elevation capable of utilizing the medium in liquid form to produce useful work. The working medium in liquid form absorbs heat at the lower elevation and produces the vapors for the condensation step, the vapors being directed from the lower elevation to the higher elevation for condensing. The composition of the working medium is adjusted to response to changes in ambient temperature to provide a system having maximum efficiency in extracting work from the working medium.

Abstract: A method and apparatus are disclosed for simultaneously determining thickness and uniformity of a supported film which is at least partially translucent by directing a beam of radiation at the film at an angle thereto, reflecting a portion of the radiation from the interface of the film and substrate back through the film, splitting a portion of the reflected radiation into a first beam portion which is monitored to determine uniformity of film thickness, and a second beam portion which is chopped and split again into a reference beam and a thickness determining beam which are filtered and transduced so that the resulting signals can be compared to determine film thickness.