June begins, the art world convenes briefly in Basel and then prepares to break for summer. But wait. An art dealerís job is never done, especially in this superheated art market. Off they go to London, to spend the summer solstice at Sothebyís and Christieís June auctions of Impressionist, modern and contemporary art, whose totals these days are within hailing distance of the big May sales in New York. Itís a great time to be an art dealer.