Let the oysters come to a boil in their own liquor. Skim well and drain. Season them with the oil, salt, pepper, vinegar and lemon juice. When cold, put in the ice chest for at least two hours.
Scrape and wash the whitest and tenderest part of the celery, and, with a sharp knife, cut in very thin slices. Put in a bowl with a large lump of ice, and set in the ice chest until serving time.
When ready to serve, drain the celery, and mix with the oysters and half of the dressing. Arrange in the dish, pour the remainder of the dressing over, and garnish with white celery leaves.