July 16, 1987

LEAD: In the cavernous ballroom of the Prince George Hotel, four boys were shooting pool, talking as tough as any New York pool sharks. One wore just his shorts, and another's face was smeared with sweat. With the boys as old as 12, they might have seemed wise about the streets - except that two of them were sucking their thumbs.

LEAD: ON their first vacation together, David and Ellen Jacoby discovered which one of them packs lots of clothes; (he does, she does not). Who likes breakfast; (he does, she does not). Who dawdles in museums; (he does, she does not). Who sends lots of postcards; (he does, she does not). Who worries that the airline will lose the luggage; (they both do).

LEAD: Despite the vast military spending by the Reagan Administration over the last six years, the armed forces today are so short of spare parts that they must cannibalize some airplanes to keep others flying.

LEAD: The Hongkong and Shanghai Banking Corporation, one of the world's largest banking organizations, offered yesterday to pay $677 million for the 49 percent of Marine Midland Banks Inc. that it does not already own.

LEAD: THE English national passion for gardening has been focused on rescuing and conserving great gardens of the past. Britain is the first country anywhere to have a Government-sanctioned register of its important historic gardens; it is being compiled by the garden historian Christopher Thacker.