volved, it is desirable that the individual wires should be fairly large, so that the outside wires shall not wear through too quickly. For standing rigging, a wire core is admissible, while for running rigging of all kinds, a hemp core is absolutely necessary. If a rope is to be exposed to the weather it must be galvanized; otherwise, not. It is important, in ordering wire-rope, to specify the purpose to which it is to be applied and as many of the conditions of its use as practicable. Plate 17 shows various types of wire rope suitable for different purposes. As a rule these types are made in the following grades of material, with tensile strength in the wire used, approximately as indicated. 1. Wrought iron, 85,000 lbs. per square inch. 2. Crucible Cast Steel, 150,000-200,000 lbs. per square inch. 3. Extra Strong Crucible Cast Steel, 180,000-220,000 lbs. per square inch. 4. Plow Steel, 200,000-260,000 lbs. per square inch. 5. Monitor Steel, 220,000-280,000 lbs. per square inch. The types illustrated are those specified for use in the United States Navy but they are standard commercial types and cover practically all the demands of seafaring practice in general and all but a few highly specialized demands of industrial practice on shore. Naval specifications call for a minimum strength in all types, of 220,000 lbs. per square inch in the wire from which the rope is made. The grades used are 3 and 4 above. 6 X 19 Type (Fig. 1). This is the stiffest and strongest type manufactured for use on ship-board. It is especially suitable for standing rigging, guys, boat slings, topping lifts, etc. It may be used over sheaves of large diameter where the speed is moderate, but has not the flexibility required for running rigging in general. This type is issued to the Navy both galvanized and ungalvanized. 6 X 37 Type (Fig. 2). This type combines strength with flexibility to a degree which makes it especially valuable for work on shipboard. It is much more flexible than the 6 × 19 type and much stronger than the 6 X 12 or the 6 X 24 type. It may be used over sheaves smaller than those for which the 6× 19 type is practicable, and is especially suitable for cranes and other machines where sheaves are necessarily rather small and where heavy weights are to be handled. It is the best rope for heavy towing, whether with or without an auto matic towing machine. When designed for towing it is galvanized and should be fitted with a thimble eye at each end. As more than 50 per cent. of the wires in a strand are on the inside, it follows that the outer wires may be considerably worn before the strength of the rope as a whole is seriously impaired. This type is issued to the Navy both galvanized and ungalvanized. 6X12 Type (Fig. 3). This is the most flexible rope made for ordinary purposes, but has only two thirds the strength of the 6 X 19 and 6 X 37 types. It is used for most of the running gear which is made of wire (except as already specified for the 6 × 37 type) and for life-lines, guys, ridge-ropes, etc. It is used also for mooring hawsers in cases where no great strength is required. It is sometimes used for towing but is not recommended for this unless with an automatic towing machine, and not then for heavy work. 6 X 24 Type (Fig. 4). This type, while inferior in strength to the 6X37 type, resembles the latter in that it represents a convenient balance of strength and flexibility. It is designed primarily for mooring hawsers to be used where greater strength is needed than that of the 6 X 12 type. It has also an advantage over the latter in that it is better fitted to stand the abrasive effect of snubbing through chocks and around bollards, because 30 per cent. of its strength is in the inside layers of its strands. Armored Wire Rope (Fig. 5). In this type each strand is wrapped spirally with flat strips of steel which protect the wires from abrasive wear. The wrapping contributes nothing to the strength of the rope but by deferring the time when the strands begin to wear, prolongs the life of the rope in some cases by as much as 50 to 75 per cent. The increase in weight and the reduction of flexibility are unimportant. Fibre Clad Rope (Fig. 6). In this type each strand is served with tarred hemp marline, which protects the wire from wear and from corrosion. It has about one-third the diameter of Manila rope of the same strength and is only slightly less flexible; admitting of coiling, belaying, and knotting, without danger of kinking. This makes it suitable for running rigging, especially for boat and crane falls, anchor gear, etc. The Manufacture of Wire Rope. The manufacture of wire rope follows closely the process already described for fibre ropes, the individual wires corresponding with the yarns of hemp and manila. The wires are twisted into strands and the strands into rope, by methods which do not differ materially from those illustrated in Plate 16. The wire used for rope is made from special ores, which are reduced by the open-hearth process to eliminate as thoroughly as possible all traces of sulphur and phosphorus, both of which impurities make for brittleness. In the various processes which follow, the metal is subjected to carefully controlled heat-treat matic towing machine. When designed for towing it is galvanized and should be fitted with a thimble eye at each end. As more than 50 per cent. of the wires in a strand are on the inside, it follows that the outer wires may be considerably worn before the strength of the rope as a whole is seriously impaired. This type is issued to the Navy both galvanized and ungalvanized. 6 X 12 Type (Fig. 3). This is the most flexible rope made for ordinary purposes, but has only two thirds the strength of the 6 × 19 and 6 X 37 types. It is used for most of the running gear which is made of wire (except as already specified for the 6 X 37 type) and for life-lines, guys, ridge-ropes, etc. It is used also for mooring hawsers in cases where no great strength is required. It is sometimes used for towing but is not recommended for this unless with an automatic towing machine, and not then for heavy work. 6 X 24 Type (Fig. 4). This type, while inferior in strength to the 6X37 type, resembles the latter in that it represents a convenient balance of strength and flexibility. It is designed primarily for mooring hawsers to be used where greater strength is needed than that of the 6 X 12 type. It has also an advantage over the latter in that it is better fitted to stand the abrasive effect of snubbing through chocks and around bollards, because 30 per cent. of its strength is in the inside layers of its strands. Armored Wire Rope (Fig. 5). In this type each strand is wrapped spirally with flat strips of steel which protect the wires from abrasive wear. The wrapping contributes nothing to the strength of the rope but by deferring the time when the strands begin to wear, prolongs the life of the rope in some cases by as much as 50 to 75 per cent. The increase in weight and the reduction of flexibility are unimportant. Fibre Clad Rope (Fig. 6). In this type each strand is served with tarred hemp marline, which protects the wire from wear and from corrosion. It has about one-third the diameter of Manila rope of the same strength and is only slightly less flexible; admitting of coiling, belaying, and knotting, without danger of kinking. This makes it suitable for running rigging, especially for boat and crane falls, anchor gear, etc. The Manufacture of Wire Rope. The manufacture of wire rope follows closely the process already described for fibre ropes, the individual wires corresponding with the yarns of hemp and manila. The wires are twisted into strands and the strands into rope, by methods which do not differ materially from those illustrated in Plate 16. The wire used for rope is made from special ores, which are reduced by the open-hearth process to eliminate as thoroughly as possible all traces of sulphur and phosphorus, both of which impurities make for brittleness. In the various processes which follow, the metal is subjected to carefully controlled heat-treat |