18 ANNUAL OF SCIENTIFIC DISCOVERY. 



tube, for the purpose of firmly connecting every set of plates to that 

 which on each side adjoins it. This work is performed by what is 

 termed " a set of riveters," composed of two riveters, one " holder-up," 

 and two rivet-boys. 



As soon as the first two have ascended the scaffolding on the out- 

 side of the tube, and when the holder-up, sitting on a board suspended 

 by ropes from the roof, has exactly opposite to them taken up his 

 position on the inside, one of the boys quickly abstracts from a travel- 

 ling furnace, conveniently placed for the purpose, a red-hot bolt, 

 which by a circular swing of his pincers he hurls inside the tube to- 

 wards the other boy, who, as actively as possible, with a similar in- 

 strument snapping it up, not only runs with it towards the holder-up, 

 but as long as he can reach the rivet-holes inserts it for him. As 

 soon as this is effected, the holder-up presses against it an enormous 

 iron hammer, which forces it outwards until it is stopped by its own 

 head. The two riveters then hammer it on the outside, so that a head 

 is formed there, and it becomes now a rivet, which, by contracting as it 

 cools, binds together the plates even more firmly than they had al- 

 ready been almost cemented by the irresistible coercion of three sledge- 

 hammers; indeed, they are so powerfully drawn together, that it has 

 been estimated that it would require a force of trom four to six tons to 

 each rivet to cause the plates to slide over each other. 



The bolts for the upper holes of the interior, which, being about 

 thirty feet high, are of course completely out of the rivet-boy's reach, 

 are dropped by him into a concentric iron ring, which, by a wire and 

 cord passing over a pulley attached <to one of the uppermost plates, is 

 rapidly raised, until the holder-up is enabled by pincers to grasp the 

 fiery iron, which, on being inserted into its hole, he then instantly, as 

 before, presses with his hammer. By the operations above described, 

 " a set of riveters" usually drive per clay about 230 rivets, of which in 

 each plate there are about 18 per yard in two rows, averaging only 2 

 inches of clear space between each bolt-head. On the large tubes 

 alone there have been employed at once as many as 40 sets of rivet- 

 ers, besides 26 " platers," or men to adjust the plates, each having from 

 three to four men to assist him ; and when this well-regulated system 

 is in full operation, it forms altogether, not only an extraordinary, but 

 an astounding scene. 



But by far the most curious part of the riveting process is to be 

 seen on the flat roof or top of the tube. This immense deck, which 

 we have already stated to be 472 feet in length, is composed of a 

 pavement of plates to be connected tog-ether by eighteen longitudinal 

 rows of rivets, the heads of which are to be only 24- inches apart. Be- 

 neath this surface, at a depth of only 1 foot 9 inches, there is, to give 

 additional strength, a similar stratum of plates, the space included be- 

 tween both being divided into eight compartments called flues, 21 

 inches deep by 20 inches broad, exactly resembling those of a com- 

 mon stove. After the horizontal bottoms and upright sides of these 

 eight flues have been firmly connected together by the battering pro- 

 cess we have just described, the upper stratum of plates is loosely 

 laid down, and, being thus by the superincumbent weight of the iron 



