RIVETING. 



BQAD. 



124 



thiu united by a natural water communication flow in the same 

 direction, or nearly so. But in South America, two Urge rivers, the 

 Orinoco and the Amaxonas, are united in this way in a part of their 

 extensive courses, where the Orinoco runs west and the Amazonas 

 mrl The branch of the Orinoco by which this natural water 

 communication is effected is called the Cassiquiare. [ORINOCO, in 

 OatM. l>iv.] This phenomenon is otherwise described as the bifur- 

 eatio* of a river high up ita course, of which the Mareb, one of the 

 tributaries of the Nile, already mentioned, affords another example. 



It is a kind of established rule, that the whole course of a river 

 should bear the same name, and that this name should be continued to 

 that branch or head-stream whose sources are farthest from the mouth. 

 But practice is frequently at variance with this rule, and in a manner 

 atrtStV* another. The inhabitants of a country preserve the name of 

 w-t river which does not undergo any deflection of its course. At the 

 confluence of the Mississippi and the Missouri, the latter is the larger 

 river, and has had a course of above 1000 miles more than the former, 

 but it does not deflect the course of the Mississippi by its junction, and 

 the name of the last-mentioned river is preserved. The same occurs in 

 South America as to the Amazonas and Madeira, where we find that 

 the last-mentioned river changes the direction of its course to meet the 

 A^-^r. M whose name is preserved. In Europe, the Rhine is joined 

 by the Aar in Switzerland, above Laufenburg. The Aar is the larger 

 river, and brings down a greater volume of water ; but the Rhine, where 

 it i* joined by it, continues its westerly course, and its name is preserved. 

 There are also two rules for determining which of the various head- 

 streams of a river is entitled to be regarded as its upper course, and 

 consequently to bear the name borne by the united stream lower 

 down : the one rule is at the same time theoretical and natural ; the 

 other is practical or conventional. By the former, the greater length 

 and size, and the general direction of the valley or basin of the river, 

 are the main considerations. By the latter, it is the first acquaintance 

 which the inhabitants or discoverers of the valley of the main stream 

 may nuke with one of ita branches (or the converse) that causes the 

 name of the former to be extended to the hitter. 



The extent of a few river basins is here given in round numbers, 

 but they must only be considered as rough approximations : 



Biven. Square Miles. 



6,500 

 60,000 

 89,000 

 108,000 

 270,000 

 312,500 

 410,000 

 443,000 

 653,000 

 707,500 

 742,000 

 1,100,000 

 1,200,000 

 2,000,000 

 2,380,000 



According to Humboldt the area of drainage of the Amazonas 

 measures 8,000,000 of square miles ; but in this he, in all probability, 

 includes that of the Tocantins [BRAZIL, in GEOO. Drv.] which Mr. 

 Wallace, correctly in our opinion, regards as a distinct river. 



UIVKTIN'G, considered in its simplest form, is nothing more than 

 the hammering of an iron bolt through a hole punched in two iron 

 plates ; but in the vast engineering operations of the present day, where 

 ire used, not merely by the thousand, but by the million, the 

 rapid and exact management of the operation become important 

 matters. The Britannia tubular bridge over the Menai was the first of 

 these great examples of rivet-fastened plates ; the Hreat Eastern steam- 

 ship was a second ; and the Victoria railway bridge over the St. 

 Lawrence, at Montreal, is a third. The rivets themselves may be 

 "imply pieces cut off from iron rods, and heated in a forge to a state fit 

 for hammering ; but under NAIL MAMIFAOTUHK will be found a notice 

 of certain machines which are equally suited for making nails, rivets, 

 nuts, and spikes. 



At a meeting of the Institute of Mechanical Engineers, in 1857, 

 Mr. Harvey made the following observations on rivets and riveting : 

 "In the manufacture of steam-boilers, the operation of riveting is 

 mostly effected by hand-labour ; and in order to bring the heads of the 

 rivets to a proper form and finish, much of the hammering takes place 

 when the rivet has approached to a nearly cold state. The tendency 

 of this is, to destroy, to a certain extent, the fibrous character of the 

 rivet. The case of a rivet-head, starting off under the operation of 

 proving the boiler, although seldom occurring, has revealed the fact 

 that a crystalline character miixt be more or less assumed by the iron 

 in all rivets worked hi the usual manner; and hence, besides ariving at 

 economy by the use of steam for riveting, it is very desirable that the 

 rivets should be finished in as short a time as possible, and without 

 that succession of blows by which the fibrous character of iron is 

 always more or less injured." In hand-riveting, it may be added, the 

 head is made conical by the shape and action of the riveting hammer; 

 whereas in steam-riveting the bead becomes convex, which is better. 

 Nevertheless, steam-riveting machines, though many have been 



Thames 



Atbara, the fertilising tributary of the Nile 



Rhine 



Euphrates, Including the Tigris . 



Brahmaputra 



Danube 



Indoi 



Ganges 



Volga 



Kile 



Yan-Ur-kiinK 



MitMsdppi 



Plata 



Objr 



Amatonas 



invented, have not hitherto come much into use. Some are found to 

 be too complex, and likely to get out of order. Some require a pres- 

 sure of steam of SO Ibs. on the square inch, with either a separate boiler 

 or a large steam-cylinder, which renders them too costly. Some have 

 a defect arising from the peculiar mode in which they act ; a cam, 

 moving through a fixed distance, and acting through a combination of 

 levers, with a fixed distance for the travel of the riveting die, is unable 

 to adapt itself to irregularities in the lengths of rivets which may 

 occur in general work, and which must occur when rivets go sometimes 

 through two, and at other times through three thicknesses of plates. 

 Messrs. Whitelaw and Harvey have endeavoured to surmount some of 

 these difficulties in a riveting-machine of recent introduction. The 

 steam-cylinder is 15 inches in diameter by 24 inches stroke. A 

 system of levers and eccentrics carry a shearer, a punch, and a die ; 

 for the machine is intended to perform all three operations of cutting 

 iron plates, punching holes in them, and then driving rivets into 

 the holes. The machine is not wholly self-acting ; it is momentarily 

 stopped by hand after every stroke. The effective action of steam is 

 upwards; the downward movement is the effect of the weight of 

 the moveable parts of the apparatus. Between the piston and tlm 

 bottom of the cylinder a portion of the exhausted steam is iv 

 as a cushion, to bring the piston softly to rest. Steam of 201b. to 

 the inch has pressure enough for this machine. It has power tn 

 punch a hole three-quarters of an inch diameter through a cold iron 

 plate three-quarters of an inch thick, and to effect the cutting and the 

 riveting for the same plate. In riveting, the action upon the rivet-held 

 is a pressure, not a blow ; this pressure becomes more and more i i 

 as the process advances, until just before the head of the rivet is finally 

 shaped, it amounts to something like 30 tons. 



In riveting, whether by hand or by machine, it is necessary to 

 furnish a pressure against one end of the rivet to assist the action at 

 the other. In the hand method, one man holds a hammer forcibly 

 against one end of the rivet in the hole, while another strikes the 

 other end. In the machine method, the action is like the pressure of 

 a die and counterdie. 



RIVULIN. A mucilaginous matter found in a species of fresh- 

 water plant, the Rirula tubulosa. 



ROAD. Under this head it is proposed to embrace road-inaking, 

 with a brief sketch of the history of roads, referring for more detailed 

 statistical information to the GEOGRAPHICAL DIVISION of this work, 

 and to WAY and TURNPIKE TRUSTS for an explanation of the laws 

 respecting the formation and maintenance of the highways in this 

 country. 



The importance attached to roads by the great nations of antiquity 

 is abundantly testified by historians, though, except in the case of the 

 Roman roads, there are few remains existing. The Carthaginians are 

 said to have been the inventors of paved roads, which were much used 

 by the Romans, who were distinguished by the vast extent and solid 

 construction of their highways, of which several thousand miles were 

 made in Italy alone, while every country which was brought under 

 their sway was more or less intersected by these channels of com- 

 munication. Though formed mainly to facilitate military movements, 

 the Roman roads were productive of the greatest civil benefits. Being 

 made by a power whose resources were almost unlimited, these military 

 roads were usually laid out in straight lines from one station to 

 another, with little regard to natural obstacles, which were frequently 

 passed by means of very extensive works, as excavations, bridge 

 in some instances, tunnels of considerable length. The solidity of 

 their construction was fully equal to the boldness of their design ; a 

 fact proved by the existence 'of many that have borne the tr, 

 near two thousand years without material injury. The Roman 

 engineers were very particular in securing a firm bottom, whieli v,a 

 done when necessary by ramming the ground with small 

 fragments of brick, &c. On this carefully prepared foundation a 

 pavement of large stones was firmly set in cement, the stones being 

 occasionally squared, but more commonly of irregular shapes, though 

 always accurately fitted to each other. For this purpose many 

 varieties of stone were used, but the preference seems to hav< 

 given to basalt, where it could be had, it being used in many situa- 

 tions in which other suitable materials might have been procured with 

 less labour and expense. Where large blocks could not be con- 

 veniently obtained, small stones of hard quality were sometimes 

 cemented together with lime, forming a kind of concrete, of which 

 masses extending to a depth of several feet are still in existence. The 

 Koman roads were generally raised above the ordinary surface of the 

 ground, and frequently had two carriage tracks separated by a raised 

 footpath in the centre. 



In some parts of the continent of Europe, especially in Italy, the 

 Roman system of road-making has been imitated, particularly in city 

 pavements ; but in Britain the attempts to follow the Roman model 

 appeal 1 to have been very limited, and road-making has been very imper- 

 fectly practised till within the last half century. Many of the existing 

 highways were originally mere paths or tracks from place to place, their 

 course having been determined more by accidental circumstance- 

 by a due attention to the properties of a good road. Thus deviat inns 

 were made from the direct course in order to cross rivers at fordaMu 

 points, and the road was conducted over a hill in preference to a more 

 level course round its base, to take advantage of natural drainage. As 



