Page:The New International Encyclopædia 1st ed. v. 17.djvu/312

ROOT TtJBERCLES. 284 BOPE. in turn, supply nitrogen to the host plant. (tSee Symbiosis.) In this way if the soil contains sufficient available nitrogen for the nia-Kimuni ilevelopnient of the plant, few tuber- cles will be developed, but well supplied with soil organisms, tubercles will be develiJi)eil in abundance. The failure of Boussingault and otliers (o observe any increase in nitrogen was due either to the absence of the micro-organisms or to a large amount of available nitrogen in the soil, since the organism {Bdcilhis radicicoUt) is not always present in the soil. Two means for securing them have been developed. One, called soil inoculation, consists in scattering soil rich in these organisms over a field to be planted, and the other in the use of cultures of the organ- isms distributed on the seed or over the soil. This last method is in some ways preferable and has resulted in the conmiercial preparation of a 'nitrogen.' See Clover; LEGUMiNO.s.i; ; Green llANi'Hi.Nd: Nitrogen. BOPE ( AS. rap, Goth, raips, OHG. reif, cord, Ger. licif, ring; of uncertain etymology). Tech- nically, cordage one inch or more in diameter. The term cordage is used in a collective sense to include all sizes and varieties of cords and rope from harvester twine to the largest cables. It is probable that rope-making was among the very earliest of human industries. The materials first used for the ]iurpose were probably the fibres of various plants, the inner bark of trees, and the hides of animals cut into thongs and twisted together. Sculptural representations of rope- making are found upon ancient Egyptian manu- scripts, showing that they made use of flax and the fibres of the date tree as well as of rawhide. ' Herodotus states that the Persians manufactured cables 28 inches in circumference of flax and papyrus with wliioh to aid in constructing the bridge of boats upon whidi the army of Xerxes crossed the Hellespont. Peruvians used fibres of the maguey for rope and twisted cables of suffi- cient strength to carry the primitive suspension bridges. Prior to the year 1820, hand labor, aided only by the clumsy wheels and other imperfect con- trivances pertaining to the old-fashioned rope- walk, was exclusively employed in the manufac- ture of rope. In that year some machines were constructed in England for twisting hand-spun yarn into strands, and a few were imported mto the l.'nited States. The next step was the intro- duction of machines for spinning the thread.s from the raw material. The first machinery for this purpose was constructed in Massachu- setts in 1834. American machines are now ex- tensively employed in Europe, and American cordage is held in such high estimation that it is exported to all parts of the world. Materials. The materials employed for rope- making include hemp, flax, cotton, manila, sisal, jute, and other vegetable fibres. Russian hemp for tarred rigging has long maintained a reputa- tion for superiority ; its great strength and dur- ability are wttributed to the method of retting the fibre under water in lieu of the mode usually adopted with American hemp, called dew-retting. Italian hemp is also of excellent quality, and for some uses is unsurpassed. Manila hemp is per- haps more extensively used in the manufacture of cordage than any other matsrial, as its great pliability and strength particularly adapt it for the running rigging of vessels and for a multi- plicity of ordinal)' uses. Russian and American hemp are jireferred for standing rigging, because they will absorb a great amount of tar and will withstand the weather without shrinking or stretching. Sisal, from Yucatan, and East In- dian jute, are largely used for the nmnufacture of the cheaper grades of cordage. See Flax; Hemp; Jute; Sisal. Rope-Walk Rope-Making. The old walk was usually from 1,000 feet to 1,400 feet long. Fibres of hemp were hackled or straightened out by drawing the material through a steel-toothed coml). The workman then wound a bundle of liemp about his body, attaching one end to one of a- series of hooks on a "whirl' or looper. draw- ing out the fibres from the bundle with one hand and compressing them with tlie other, ex- ))erience teaching the number of fibres to draw out and how to twist them so as to hold firmly to the hook. He then walked slowly backward down the walk, making his .yarn as he went, the spinning being done by the wheel or 'whirl' turned by an assistant, the spinner seeing that the fibres were equally supplied and joining the twisted parts at the ends. Two or more spin- ners might be going down the walk at the same time and at the end two would join their yarns together, each then beginning a new yarn and re- turning on the walk to the end where the second spinner again took his yarn off the 'whirl' and joined it to the end of the first spinner's yarn, so that it continued on the reel. When a suffi- cient number of yarns were spun they were twisted into strands and the strands into ropes, horse power being usually employed. A CABLE-LAID ROPE. The next improvement was the introduction of machines for twisting the yarn into strands and laying the strands into cables. The nature and operation of these machines can best be explained by describing a modern rope-walk plant, the reader taking care to remember, however, that, at first, hand-spun yarn was employed instead of the present machine-spun yarn, ilost large rope, such as towing lines and ship cables, is walk- laid rope. The first operation is to wind the yarn on large bobbins. These bobbins are put on a framework of wood located near one end of the