146 



NA TURE 



[Dec. 



187; 



of African oak, placed longitudinally upon these, thus 

 forming a rude railway. Rollers consisting of the un- 

 worked tubes of guns were then obtained from the gun 

 factories, and laid across the planks. A sleigh, composed 

 of two massive bars of wrought-iron turned up in front, and 

 attached together by baulks of timber, was then placed 

 upon the rollers, and surmounted first by the cast-iron plate 

 to be carried, then by a movable or revolving crane. The 

 sleigh being drawn forwards by a crab-winch and tack- 

 ling, as the rollers were successively passed over the crane 

 lifted up those that were behind, and, swinging round, de- 

 posited them in front, presenting a fresh rolling surface 

 upon each occasion. Thus the plates were each slowly 

 moved from the foundry to the foundation pit. But there 

 was another difficulty. As it was necessary to have 

 "joggles," or projections npon the summit of several of 

 the plates for the superincumbent ones to rest within, and 



in open castings it was impossible to cast them upon an 

 upper surface, the joggles had to be formed upon the lower 

 surface, and the plates to be reversed in position after- 

 wards. This was done by casting trunnions upon the 

 edges of the plates, nearer one end than the other, and 

 then swinging the plates over the foundation pit by these 

 trunnions, until the heavier half descended, drawing back 

 the heavier portion by a crab-winch, and finally permitting 

 the lighter portion gradually to descend, the trunnion 

 supports being withdrawn, and the edge of the plate 

 resting on the ground forming a fulcrum. The trunnions 

 do not appear in our engraving, but the joggles may be 

 seen upon the three upper sets of castings. 



We will now revert to the laying of the foundations. 

 Over the whole extent of the lower plates a thin layer 

 of rock-elm planks was laid, this being the most inde- 

 structible kind of v^'ood known, it being necessary to 



I, Proposed floor ; 



, Present ground Iln 

 6, Tv 



Foundations for 30-ton Steam Ha 

 : 3, Single block weighing 98 tons: 4, T 

 ) blocks of 75 tons each ; 7, Oak baulks cri 



produce a perfectly even surface for the baulks of timber 

 which come next. These were of oak, thirty feet long, 

 and a foot square. Upon the baulks of oak rest two 

 more plates of cast-iron, twenty-seven feet long, and 

 thirteen feet si.K inches wide, and weighing each seventy- 

 five tons. Tliey are connected by huge dove-tails cast 

 into the metal itself, as are also the two lower ones, and 

 all the other plates v,'hich are in the same horizontal plane. 

 A liquid called "grouting," formed of very thin watery con- 

 crete, is poured in between the joints of the plates so as to 

 fill up all interstices, and holes are made in several places 

 through the castings, so as to admit of the grouting 

 freely percolating everywhere. Upon the two plates 

 are more planks of rock-elm, and then a layer of 

 oak stumps two feet three inches long, placed upright, and 

 surrounded by a band of wrought-iron, six inches wide 

 by two inches thick. All the remainder of the foundation 

 pit was filled in with concrete as the work gradually pro- 

 ceeded upwards. Upon the oak stumps are two plates, 



weighing each si-xty-five tons, and forming a square 

 of twenty-four feet. A thin layer of rock-elm planks 

 separates them from a huge single casting, twenty-two 

 feet square, and weighing very nearly loo tons. Wedges 

 within the joggles of the 65-ton plates fix firmly the 

 single one above, and it in its turn supports the enor- 

 mous anvil block weighing 103 tons, over which will come 

 the anvil itself, but that is not yet in position. The anvil 

 block was cast in a closed mould, which rested upon a 

 substratum of coke and bricks with passages left filled 

 with straw for the exit of the gas generated ; it took, 

 nevertheless, six months to cool, and could not be re- 

 moved until after the manufacture and removal of several 

 subsequent castings. Such is a short review of the 

 principal features in the construction of these foundations ; 

 all other information as to details in dimensions, iS:c., 

 may be obtained from the accompanying engraving. 

 About 660 tons of metal have been made use of in com- 

 pleting them. 



