Length.

No. to lb.

4 inches, . .

. 8

5 "...

. 437

6 "...

. 4.2

7 "...

. 275

8 "...

. 174

9 "...

. 1.55

10 "...

. 1.15

Professor W. R. Johnson found that a plain spike "375 inch square, driven 3 3/8 inches into seasoned Jersey yellow pine or unseasoned chestnut required a force of about 2,000 lbs. to extract it; from seasoned white oak, about 4,000 lbs.; and from well-seasoned locust about 6,000 lbs.

Everyone is familiar with the fact that a piece of rusty iron, wrapped in cotton or linen cloth, soon destroys the texture of the fabric. A rusting nail, for example, if laid upon a few rags, will soon produce large holes in them; or it will, at least, render every point that it touches so rotten that the cloth will readily fall to pieces at these points, and holes will be produced by the slightest hard usage. From this well-known fact we may draw the conclusion that iron, during the process of rusting, tends to destroy any vegetable fiber with which it may be in contact. This explains, to a certain extent, the rapid destruction of the wood that surrounds the nails used in outdoor work, whereby the nail is soon left in a hole much larger than itself, and all power of adhesion is lost. Part of this effect is, no doubt, due to the action of water and air, which creep along the surface of the nail by capillary attraction, and tend to produce rottenness in the wood as well as oxidation in the iron. But when we compare an old nail-hole with a similar hole that has been exposed during an equal time, but filled with a wooden pin instead of an iron nail, we find that the wood surrounding the wooden pin has suffered least; and we may, therefore, fairly attribute a destructive action to the rusting of the iron. It might, at first sight, be supposed that, as the oxide of iron is more bulky than the pure iron, the hole would be filled more tightly and the nail held more firmly to its place. But, although this effect is produced in the first instance, yet the destruction of the woody fiber and the pulverization of the oxide soon overbalance it, and the nail becomes loose. Of course, the iron itself being also destroyed, its strength is diminished; and we have, therefore, a double incentive for preventing or diminishing the action that we have described. The only way to prevent this action is to cover the nail with some substance that will prevent oxidation. This might be done by tinning, as is common with carpet-tacks, which are now extensively tinned for the purpose of preventing them from rusting, and thus rotting holes in the carpets. Coating them with oil or tallow would be efficient, if the act of driving did not remove the protecting matter entirely from a large portion of the surface. But, even then, it will be found that the oil or fat is stripped off the point and gathered about the head in such a way as to prevent the entrance of air and moisture into the hole.

The most efficient way to coat nails with grease is to heat them to a point sufficient to cause the grease to smo':e, and then pour the grease over them, stirring them about in a pot or other vessel. When the nails are hot, the melted grease will attach itself to them more firmly than it would have done if they were cold. Indeed, so firmly that it will require actual abrasion of the metal to separate it. In erecting fences, laying plank or board sidewalks and the like, it becomes an important matter to secure the nails against the influence that we have mentioned, and vet the work must be done rapidly and cheaply. Nails may be readily prepared as described, or they may simply be dipped in oil or paint at the moment when they are driven in. And we have found, by experience, that in cases where it is not advisable to paint the whole fence, it is, nevertheless, a good plan to go over the work and touch the head of every nail with a brush dipped in oil or paint prepared so as to be of the same color as old wood.