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Varves and Summers, As the geologists fanned and mopped themselves in a temperature of 91°, Dr. Ernst Valdemar Antevs, who was born in cool Sweden and now lives in cool Maine, blandly told them they were enjoying a period of cool summers which began 4,500 years ago and would last 6,500 years more. Germany's Dr. Rudolf Spitaler first suspected that the northern hemisphere has warm summers when the eccentricity of earth's orbit swings it close to the sun during the northern summer.
This condition, he found, obtains for periods of roughly 11,000 years, then lapses for an equal period while the southern hemisphere takes its turn. Confirmation of this astronomical hypothesis Dr. Antevs had last week in varves: layers of sediments deposited, one layer a year, by melting glaciers. The varves are light-tinted when glacial ice melts fast (hot summers), dark-tinted when it melts slowly (cool summers). Dr. Antevs counted and deciphered 35,000 varves, found a cycle of alternately cool & warm summers in close agreement with the Spitaler calculations.
First Continents, More than 100,000,000 years ago the hideous, ungainly reptiles which were then the lords of life roamed two vast continents, ''Gondwanaland" in the southern hemisphere, "Laurasia" in the northern. A globe-girdling ocean, the "Tethys Deep," divided them. Mighty Gondwanaland shuddered, cracked and sundered. Its fragments drifted to form South America. Africa. Australia, Peninsular India, Madagascar. Mighty Laurasia similarly broke to form North America and Eurasia.
This dramatic cataclysm was prosaically described last week in an effort to show that it was true. Its describer was Dr. Alexander Du Toit of Johannesburg who, defending the widely held ''displacement hypothesis," brought into court recent studies of fossils, glacial records and sedi mentary rocks of southern lands now separated by water. So much alike are these records at corresponding stages, urged Dr. Du Toit, that they must have been deposited in one undivided land. But the geological record of the southern hemisphere as a whole is utterly different from that of the northern—which would show that mighty Gondwanaland and mighty Laurasia were divided by some such mighty barrier as the "Tethys Deep."
How the "Tethys Deep" was bridged by Central America was indicated by Yale's Dr. Hellmut de Terra. With the cooling and shrinking of earth's underlying shell of magmatic (semifluid) rock, the northern and southern land masses drew toward each other. Pinched between them, the bottom of the "Tethys Deep" wrinkled, bulged upward, finally, as the pressure increased, emerged from the water to form a bridge.*
Cosmic Ripples. Dr. Arnold Heim. famed oil & mining consultant, attended the I. G. C. as a delegate of the Swiss Government and the Swiss Academy of Science. Landing in Manhattan last month, he made news by promising to disclose a new theory to explain the twitchings that have changed earth's face. Last week he kept his promise. First with merciless logic he assailed the old thesis that earth's crustal movements represented the spending of terrestrial energy.