CREATE TABLE table_30839 ("By-election" FLOAT, "Electorate" TEXT, "Date" TEXT, "Incumbent" TEXT, "Reason" TEXT, "Winner" TEXT)

When james seaton is the incumbent what is the reason?
SELECT "Reason" FROM table_30839 WHERE "Incumbent" = 'James Seaton'
SELECT "Reason" FROM "table_30839" WHERE "Incumbent" = 'James Seaton'