CREATE TABLE table_18478 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

John W. Heselton was first elected in what year?
SELECT MAX("First elected") FROM table_18478 WHERE "Incumbent" = 'John W. Heselton'
SELECT MAX("First elected") FROM "table_18478" WHERE "Incumbent" = 'John W. Heselton'