CREATE TABLE table_36243 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT)

What was the district Incumbent Julius Kahn was in that was smaller than 1906?
SELECT "District" FROM table_36243 WHERE "First elected" < '1906' AND "Incumbent" = 'julius kahn'
SELECT "District" FROM "table_36243" WHERE "First elected" < '1906' AND "Incumbent" = 'julius kahn'