Abstract: Presented is a new type of heat engine and process cycle utilizing, through the medium of superconductivity, a singular high temperature heat reservoir as a source of motive fuel directed into a low temperature region, the net effect being to cyclically process a superconductive substance magneto-calorically in H-T space so as to convert a thermal energies input directly into an available work energies output, without any need for a pressed, externally derived temperature variation, nor low temperature reservoir, for absorption of waste heats, to accomplish same, and which process is adaptable for both the direct generation of mechanical energy or electrical energy, in either mode being called a "Keefengine". The process of such conversions of ambient heat into utilizable work being called "Thermosynthesis", and being the product of the thermodynamic cycling of an "Envelopment", consisting of any number of mutually insulated "Segments" of size "d", where .sqroot.5.lambda.(T)<d<.xi.