London — Its eyes on a future in which North Sea oil will be only a memory, Britain is beginning to probe and gently exploit the resources of geothermal energy lying deep beneath the surface of the land.
Focus of one important investigation is a tiny quarry shaft in Cornwall above the vast granite "spine" of England's southwest. Engineers at Rosemanowes near Camborne have begun boring a 6,000-foot hole.
The aim is to build a shaft down which cold water will be pumped. At the bottom it will hit hot granite, and then be pumped to the surface again at temperatures of up to 80 degrees C. (176 degrees F.).
If the technology works satisfactorily, a deeper shaft will be sunk. Eventually water heated to 175 degrees C. (347 degrees F.) and in the form of steam for power generation will hiss to the surface.
Scientists believe southwest England promises to be a highly productive source of geothermal steam, a form of energy that an oil- and coal-rich nation has been slow to exploit.
Other countries, less well-endowned with other energy resources, have been faster. Italy uses geothermal steam to produce electricity. In Hungary it is used to heat buildings. In France half a million houses will be heated geothermally by the end of this decade. Reykjavik, the capital of Iceland relies almost entirely on geothermal energy.
While the Cornwall experiment goes ahead, Southampton, in southern England, is beginning a project that will use hot water, already lying in large quantities beneath the city, as an important source of heat for buildings.
A deep bore-hole is being sunk, and hot water bubbling to the surface at around 75 degrees C. (167 degrees F.) will heat a large shop and office complex, a factory, a civic center, and swimming pools.
The Southampton scheme will generate only a modest quantity of heat -- about three megawatts. But if it proves successful, engineers will begin turning their attention to other parts of the country where quirks of geology offer hope of significant energy exploitation.
The east Midlands and central Scotland are among areas where scientists believe heat could be unlocked and turned to man's use.
Workers on the Cornwall project concede that the capital cost of a full complex of hot rock bore-holes would be high, but against this they point out that North Sea oil will probably be running out at the end of the century.
The environmental impact of hot rock energy extraction is said to be moderate.
An important attraction of hot rock energy is its suitability for harnessing to secondary industrial activity immediately adjacent to the heat source.
The project in Cornwall is comparable to work on hot rocks currently under way at Los Alamos, New Mexico.