40 ANNUAL OF SCIENTIFIC DISCOVERY. 



pension bridge at Niagara is only two hundred and thirty feet high, 

 and no longer than this. Some more definite idea of this immense 

 structure may be gathered from the following statistics; --rising from 

 the bed of the river are eight stone abutments, each thirty feet high. 

 On these rest the truss work of wood, extending one hundred and 

 ninety feet above the abutments. On the top of this structure stands 

 the bridge itself, which is fourteen feet high. The base of the truss 

 work is seventy-five feet in width, and the top of the bridge, twenty- 

 five feet. To furnish the timber for it, over two hundred and fifty 

 acres of land have been required. More than a million and a half 

 feet of timber, board measure, have been used in the construction, 

 together with sixty tons of iron in bolts. The work was completed in 

 eighteen months at a cost of about $140,000. The bridge was 

 designed by Mr. H. C. Seymour, and so perfect is the model, that from 

 the supporting truss-work any piece of timber can be removed, in 

 case it becomes defective, and a new one placed in its stead, without 

 affecting the strength of the work, or displacing any other timber. 

 The truss-work is composed chiefly of timbers placed on their ends in 

 an upright position, and so braced, and counter-braced, and the whole 

 structure made so firm, that it is estimated it will sustain with safety 

 twenty times the weight of any train that can pass over it. 



NOVELTIES IX SHIP BUILDING. 



THERE is now building at the Clyde, at Carts' Dyke, an immense 

 iron steamship, to be called the Atrato, of much greater capacity and 

 considerable larger, than that leviathan steamer, the Great Britain ; 

 indeed so large is the Atrato to be, that the Cunard steamship Arabia, 

 of 2,400 tons, might be put inside the new steamer, with a good deal 

 of room to spare. 



The origin of the Atrato is somewhat singular. Her builders, hav- 

 ing constructed the engines (of 850 horse power) for the Demerara, 

 which got jammed across the Severn, and had to be broken up in 

 strains she received, got an order from the West India Mail Steam- 

 ship Company, to whom the Denierara belonged, to build a vessel of 

 iron instead of wood, to which the new engines might be adapted. 

 They were permitted to modify the design of the hull so far as the 

 length was concerned, although the retention of the original paddle- 

 shafts compelled an adherence to the same breadth of beam at that 

 line as the original vessel. The result has been that the engineers 

 submitted plans which were approved of, and are now being carried 

 out in the building of the largest vessel ever afloat. The entire length 

 of the keel is laid resting on blocks. The enormous bar is in nine 

 pieces, joined by scarf-joints, and firmly riveted together. The stern 

 post is in one piece, and so is the stem, which runs for about ten feet 

 into the horizontal keel. The stem alone weighs 65 cwt. Only one- 

 half of the ribs or frames are as yet in place, and even with the long 

 length of bare keel terminated by the stem standing up some forty 

 feet or more, the enormous dimensions of the vessel can hardly be 



