On which date was the class 157?
CREATE TABLE "hugh_smellie_1878_1890" (
  "class" real,
  "date" text,
  "builder" text,
  "no_built" real,
  "1919_nos" text,
  "lms_class" text,
  "lms_nos" text
);
SELECT "date" FROM "hugh_smellie_1878_1890" WHERE "class"=157;