The wire ordinarily used is No. 12, except for the top wire in the Kniffin training, which is usually No. 10, as the greater part of the weight is then upon the top wire. No. 9 is sometimes used, but it is heavier than necessary. No. 14 is occasionally used for the middle and upper rows in the upright systems, but it is not strong enough. The following figures show the sizes and weights of these and similar iron and steel wires: No. Diameter in inches. Weight of 100 feet. Feet in 2,000 pounds. 9 .148 5.80 pounds. 34,483 10 .135 4.83 " 41,408 11 .120 3.82 " 52,356 12 .105 2.92 " 68,493 13 .092 2.24 " 89,286 14 .080 1.69 " 118,343 15 .072 1.37 " 145,985 16 .063 1.05 " 190,476 The plain annealed iron wire costs about 3 cents per pound, and the galvanized--which is less used for vineyards--3-1/2 cents. Of No. 12 wire, about 160 pounds is required per acre for a single run on rows eight feet apart, and about 500 pounds for three runs. The cost of No. 12 wire per acre, for three runs, therefore, is about $15. The wire is secured to the intermediate posts by staples driven in firmly so that the wire will not pull through readily of its own weight, but still loosely enough to allow of the tightening of the wires. In other words, the head of the staple should not quite touch the wire. Grape staples are of three lengths, about an inch, inch and a quarter, and an inch and a half respectively. The shortest length is little used. The medium length is used for hard-wood posts and the longest for soft posts, like chestnut and cedar. These staples cost five cents per pound usually, and a pound of the medium length contains from 90 to 100 of the No. 10 wire size. An acre, for three wires, will therefore require, for this size, about nine or ten pounds of staples. In windy regions, the wires should be placed upon the windward side of the posts.