Cream together oil and sugar. Add potatoes and continue creaming. Mix in molasses. Sift together the flour, soda, spices, and salt. Stir into the first mixture. Drop the batter by tablespoonfuls onto greased baking sheets. Flatten to a thickness of 0 cm, using a greased flat bottomed glass. Bake at 350 degrees until the cookies are lightly browned, about 15 minutes. Remove from the baking sheet and cool. Makes about 30 cookies.