WHEN scientists, a cautious lot, are on the frontier of knowledge, they are fond of the word "perhaps." At Los Alamos Scientific Laboratory they like the word so much that they named one of their most exciting machines the Perhapsatron S-3. Perhaps the Perhapsatron and its descendants will win from the world's oceans enough energy to fill man's electric power needs for as long as the solar system exists. For the latest steps in taming the H-bomb for peacetime power, see SCIENCE, Toward H-Power.

THE cover subject of TIME'S fourth issue, back in 1923, was Turkey's late, great Mustafa Kemal Ataturk. Since then, TIME has followed Turkey's drive to become a modern nation with many a continuing story, this week stops for a comprehensive look at the man many consider the greatest Turk since Ataturk. See FOREIGN NEWS, The Impatient Builder.

AS unarmed schoolboys hurled stones at police lorries and civilian freedom fighters stood up to machine-gun fire, Venezuelan Dictator Marcos Peerez Jimenez toppled with a crash that rattled the Americas' few remaining strongmen. Struggling to avoid a similar end at the hands of mountain guerrillas who have been battling for his overthrow, Cuba's President Fulgencio Batista relaxed his grip on civil rights, prepared to set up what he hoped would be a well-controlled election. And Guatemala, following its second try at presidential elections in three months, hovered at the brink of violence while Congress tried to decide who won. For a rundown of the week's loud bangs and smoldering fuses, see THE HEMISPHERE.

CONTENTED cows used to get that way on their own; now they are put on tranquilizers. As for old dogs, they are taught new tricks, according to the latest scientific principles of geriatrics and psychology. In the last two decades, veterinary medicine in the U.S. has made giant forward strides paralleling human practice ever more closely in medication and surgery. For an account of how vets and pets are getting along, see MEDICINE, Veterinary Revolution.

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