o2 ANNUAL OF SCIENTIFIC DISCOVERY. 



eastern end being 100 feet in diameter, and that of the western end about 133 

 IcL-t in diameter. 



The military port of Cherbourg consists of an outer harbor, 77GJ feet long, 

 by GG2| feet wide, with a minimum depth of water of 58^ feet. The channel 

 at the entrance is 20G feet wide at the narrowest point, and is usually 530 feet 

 wide. The cost of this outer harbor was estimated at nearly 080,000. Be- 

 yond it, and communicating with it by means of a lock of about 130 feet 

 long, and 58 feet 7 inches wide, is a floating basin 957 feet long by 712 feet 9 

 inches wide. There are on the opposite side of the outer harbor to this float- 

 ing basin, four fine covered building-slips for 120-gun ships, and a graving 

 dock close by a caisson, besides some uncovered slips for building smaller 

 classes of ships. The building-slips for vessels of the line are 383 feet long, 

 by 78 feet 8 inches Avide. The graving-dock is 245 feet long, by about 78 feet 

 wide, with a depth of water over the sill of about 27 feet 6 inches. 



The inner floating harbor has been inaugurated. It is parallel to the first 

 floating basin, and will communicate both with the outer harbor and the 

 basin. It is about 2788 feet long by about 1312 feet wide, and is entirely 

 excavated out of the solid rock, a member of the transition series, ex- 

 tremely hard and tough. All round this marvellous sheet of water is a series 

 of graving-docks and building-slips, of remarkable beauty, so far as we may 

 judge of them by their present state, at least; and immediately beyond the 

 qua} r s are the various magazines, storehouses, sail-lofts, shops, etc., which, 

 when complete, will render Cherbourg one of the most complete arsenals in 

 Europe. 



THE VICTORIA (ST. LAWRENCE) TUBULAR BRIDGE. 



The present year will witness the completion of, perhaps, the greatest 

 engineering work of our time, viz., that of the great bridge across the river 

 St. Lawrence, of which the Britannia Bridge over the Menai Straits proves 

 to have been but the precursor, as to Americans it will hereafter seem but as 

 the shadow. The enterprise has been carried out under the auspices, and as 

 a part of the " Grand Trunk Railway," w r hich forms the connecting link 

 between Montreal and the United States. In order that this road might be 

 kept open in winter, a bridge across the St. Lawrence, near Montreal, was 

 absolutely necessary; but the difficulties of crossing the river at this point 

 seemed at first almost insuperable. Its width, even at the most available 

 point is very formidable; its current is very rapid, its depth not insignificant. 

 Besides this, the navigation of the river, not merely by steamboats and other 

 vessels, but by enormous timber rafts, had to be provided for; so that un- 

 usual elevation, and unusual width between the piers, were both required. 

 There was another obstacle, more formidable far more formidable than 

 all. In the winter season, the St. Lawrence presents a field of ice from 

 three to five feet thick. Whilst it is thus frozen, the river rises sometimes as 

 much as twenty feet above its summer level. This rise of water might be 

 provided for; but how was accident to be avoided, at the annually recurring 

 period when the breaking up of the ice, with almost resistless power, sweeps 

 almost every obstacle before it ? 



Could any bridge be devised to withstand these formidable difficulties ? If 

 possible, how was such a bridge to be constructed? The Directors of the 

 Grand Trunk Railway, to whom these questions were so vitally important, 

 look a course which will probably be thought to redound greatly to their 



