PRESIDENT SPEAKS ON BELGIAN INVASION. WASHINGTON, D.C. MAY 10. PRESIDENT ROOSEVELT TONIGHT ADDRESSED THE EIGHTH AMERICAN SCIENTIFIC CONGRESS AT CONSTITUTION HALL AFTER ONE OF THE BUSIEST DAYS IN HIS ADMINISTRATION FOLLOWING THE GERMAN INVASION OF BELGIUM, HOLLAND, AND LUXEMBOURG. SEEMING WEARY, HE TOLD THE GROUP THAT THE UNITED STATES WAS SADDENED BY THE WAR, BUT THAT HE WAS PROUD THAT IT WAS SAD