Plausible Pebbles

New evidence that Africa and South America may be parts of a single continent that have drifted apart came from British geologists. They reported finding gorceixite pebbles in Africa's Sierre Leone (south of Dakar) and the Gold Coast.

Gorceixite is a rare mineral that is quite worthless except as an indication that diamonds may be found near by. But the significance of the discovery had nothing to do with diamonds. It had to do with the fact that hitherto gorceixite has been found only in Brazil, whose bulge, if slid eastward around the globe, would fit neatly into the Gulf of Guinea, against the shores of Sierre Leone and the Gold Coast.

Some competent geologists admit the plausibility of the continental drift theory, which holds that all the continents were once a single big land mass, "Angaea," surrounded by water. Angaea was presumably broken up and dispersed by 1) the centrifugal force of the planet's spinning, 2) the gravitational pull of sun and moon. The breakup is supposed to have tilted the earth's axis to its present screwy angle.

Favorite quarrel among geologists is whether or not the continents are still drifting. One school holds that Greenland and Scotland are 60 feet farther apart every year, that the distance between Paris and Washington increases a foot a year. Others insist that it will take many more years of astronomical measurement and scientific study of latitude and longitude to prove any drift at all.

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