This, we are informed, they have done, with the most satisfactory results, during the last five or six months; and they have a set of springs which ran during that time between 2,000 and 3,000 miles, besides which there are several of these spring engines in daily use.--_Iron_. [Illustration: FIG 1. IMPROVED SPRING TRACTION ENGINE.] [Illustration: FIG. 2] * * * * * TABLE SHOWING THE RELATIVE DIMENSIONS, LENGTHS, RESISTANCES, AND WEIGHTS OF PURE COPPER WIRE. DIAMETER | AREA | B.W.G Inch. Milli- | Circu- Square Square No. metres | lar inches. Milli- | Mils. metres. | 0000 .454 11.5313 | 206116 .161883 10.4435 000 .425 10.795 | 180625 .141862 9.152 00 .38 9.6518 | 144400 .113411 7.3165 0 .34 8.6358 | 115600 .0907922 5.8573 1 .3 7.620 | 90000 .070686 4.5602 2 .284 7.2134 | 80656 .0633472 4.0867 3 .259 6.5784 | 67081 .0526854 3.3989 4 .238 6.0451 | 56644 .0444881 2.8701 5 .22 5.5879 | 48400 .0380133 2.4523 6 .203 5.1561 | 41209 .0323655 2.088 7 .18 4.5719 | 32400 .0254469 1.6417 8 .165 4.1909 | 27225 .0213825 1.3794 9 .148 3.7591 | 21904 .0172034 1.1098 10 .134 3.4035 | 17956 .0141026 .9096 11 .12 3.0479 | 14400 .0113097 .7296 12 .109 2.7701 | 11881 .00933133 .60199 13 .095 2.4129 | 9025 .0070882 .4573 14 .083 2.1082 | 6889 .00541062 .34906 15 .072 1.8288 | 5184 .00407151 .2486 16 .065 1.6510 | 4225 .00331831 .21407 17 .058 1.4732 | 3364 .0026421 .17045 18 .049 1.2446 | 2401 .00188574 .12165 19 .042 1.0668 | 1764 .00138544 .0894 20 .035 0.8890 | 1225 .000962115 .06207 21 .032 0.8128 | 1024 .00080425 .05188 22 .028 0.7112 | 784 .000615753 .03972 23 .025 0.635 | 625 .00049087 .03167 24 .022 0.5588 | 484 .000380133 .02452 25 .02 0.508 | 400 .00031416 .02027 26 .018 0.4571 | 324 .000254469 .01642 27 .016 0.4064 | 256 .000201062 .01297 28 .014 0.3556 | 196 .000153938 .00993 29 .013 0.3302 | 169 .000132732 .00856 30 .012 0.3048 | 144 .000113097 .007296 LENGTH AND WEIGHT B.W.G Pounds Pounds Pounds Pounds Feet Yards 1.000 feet Miles No. per per per 1.000 per per lb. per lb. per lb. per lb. foot. Yard ft. mile.