One of our exchanges mentions an experiment which was made twenty-seven years ago, of dipping shingles into hot linseed oil prior to nailing them on the roof: and although they have not been painted, they are said to continue perfectly sound as when first put on. They were of the common pine, and as much exposed as roofs in general. This instance may be sufficient to establish the fact that shingles thus prepared, will last longer without painting than they could possibly be preserved by painting in the usual way. As a security against fire, however, we should recommend that they be first dipped in a hot solution of common salt; and afterward, when dry, be dipped in the hot oil. The expense will be trifling, and there can be no doubt of their durability, and there will be no danger of their taking fire from sparks or cinders.