GALVANIZED IRON WIRE FOR TELEGRAPH AND TELEPHONE LINES. (Trenton Iron Co.) WEIGHT PER MILE-OHM.-This term is to be understood as distinguishing the resistance of material only, and means the weight of such material required per mile to give the resistance of one ohm. To ascertain the mileage resistance of any wire, divide the "weight per mile-ohm" by the weight of the wire per mile. Thus in a grade of Extra Best Best, of which the weight per mile-ohm is 5000, the mileage resistance of No. 6 (weight per mile 525 lbs.) would be about 9% ohms; and No. 14 steel wire, 6500 lbs. weight per mile-ohm (95 lbs. weight per mile), would show about 69 ohms. Sizes of Wire used in Telegraph and Telephone Lines. No. 4. Has not been much used until recently; is now used on important lines where the multiplex systems are applied. No. 5. Little used in the United States. No. 6. Used for important circuits between cities. No. 8. Medium size for circuits of 400 miles or less. No. 9. For similar locations to No. 8, but on somewhat shorter circuits; until lately was the size most largely used in this country. Nos. 10, 11. For shorter circuits, railway telegraphs, private lines, police and fire-alarm lines, etc. No. 12. For telephone lines, police and fire-alarm lines, etc. Nos. 13, 14. For telephone lines and short private lines: steel wire is used most generally in these sizes. The coating of telegraph wire with zinc as a protection against oxidation is now generally admitted to be the most efficacious method. The grades of line wire are generally known to the trade as Extra Best Best" (E. B. B.), "Best Best" (B. B.), and "Steel." "Extra Best Best" is made of the very best iron, as nearly pure as any commercial iron, soft, tough, uniform, and of very high conductivity, its weight per mile-ohm being about 5000 lbs. The Best Best" is of iron, showing in mechanical tests almost as good results as the E. B. B., but not quite as soft, and being somewhat lower in conductivity; weight per mile-ohm about 5700 lbs. The Trenton "Steel" wire is well suited for telephone or short telegraph lines, and the weight per mile-ohm is about 6500 lbs. The following are (approximately) the weights per mile of various sizes of galvanized telegraph wire, drawn by Trenton Iron Co.'s gauge: 14. No. 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, TESTS OF TELEGRAPH WIRE. The following data are taken from a table given by Mr. Prescott relating to tests of E. B. B. galvanized wire furnished the Western Union Telegraph Co.: JOINTS IN TELEGRAPH WIRES.-The fewer the joints in a line the better. All joints should be carefully made and well soldered over, for a bad joint may cause as much resistance to the electric current as several miles of |