Professor W. R. Johnson found that † This supposes the joint and chair to rest upon a tie; but when long chairs are used, with a view of placing the rail-joint between two ties laid near each other, there will be 8 spikes to a joint; or 1,760 per mile more than above; equal to 880 pounds; making in all, per mile single track, say 12,000 spikes, or 6,000pounds, or 40 kegs.

* The price of spikes, and of cut nails, in Philadelphia, in 1873, about 5 cents per pound. Rivets 16 cents.

‡ This allows that turnouts and sidings amount to about 1 mile of extra track On 15 miles of road >a plain spike '375, or $ inch square, driven 3 3/8 inches into seasoned Jersey yellow pine, or unseasoned chestnut, required about 2000 pounds force to extract it; from seasoned white oak, about 4000; and from well-seasoned locust, about 6000 pounds. Bevan found that a 6-penny nail, driven one inch, required the following forces to extract it: Seasoned beech, 667 pounds; oak, 607; elm, 827; pine, 187.

Recent careful experiments in Hanover, Germany, by Engineer Funk, give from 2465 to 8940 pounds (mean of many experiments, about 3000 pounds) as the force necessary to extract a plain ½ inch square iron spike, 6 inches long, wedge-pointed for one inch (twice the thickness of the spike), and driven 4½ inches into white or yellow pine. When driven 5 inches, the force required was about 1/10 part greater. Similar spikes, 9/16 inch square, 7 inches long, driven 6 inches deep, required from 3700 to 6745 pounds to extract them from pine; the mean of the results being 4873 pounds. In all cases about twice at much force was required to extract them from oak. The spikes were all driven across the grain of the wood. Experience shows that when driven with the grain, spikes or nails do not hold with much more than half as much force.

Jagged spikes, or twisted ones (like an auger), or those which were either swelled or diminished near the middle of their length, all proved inferior to plain square ones. When the length of the wedge point was increased to 4 times the thickness of the spike, the resistance to drawing out was a trifle less.

When the length of the spike is fixed, there is probably no better shape than the plain square cross-section, with a wedge point twice as long as the width of the spike, as per Fig. 44.

Fig. 44.

Boards of oak or pine, nailed together by from 4 to 16 tenpenny common cut nails, and then pulled apart in a direction lengthwise of the boards, and across the nails, tending to break the latter in two by a shearing action, averaged about 300 to 400 pounds per nail to separate them; as the result of many trials.