ENGINEERING. (To WING STEAMERS, ST. CLAIR RIVER TUNNEL.) 



283 



and boilers are all below deck, so that the space 

 usually occupied by them is saved for passengers 

 and teams. The estimated saving in these re- 

 spects amounts to about 20 per cent., the room 

 being chiefly gained for trucks and carriages. 

 The absence of the side wheels also opens the 

 passenger cabins throughout the length of the 

 boat, the troublesome narrow passage between 

 the cabins fore and aft being done away with, 

 increasing the capacity for passengers about 35 

 per cent. Many attempts have previously been 

 made to employ boats with propelling screws at 

 both ends, but heretofore they have not been 

 very successful. The " Bergen " has been in use 

 for some months, and appears to fulfill all that 

 was expected of her. It has been found that 

 one of the chief obstacles to ferry navigation in 

 this latitude is the accumulation of ice in the 

 ferry slips. This ice, when it is ground up into 

 small and partly spherical pieces, forms to a 

 great depth in the slips, and paddle wheels are 

 often powerless to overcome its resistance. It 

 has been customary for the ferry companies to 

 keep tug boats with screw propellers on purpose 

 to drive the ice out of the slips, so that the 

 paddle-wheel boats could do their work. The 

 new boat with a screw at either end, both work- 

 ing in the same direction, creates powerful sub- 

 marine currents, which carry the ice toward the 



coal and iron from the west Superior region 

 down to the lower lakes. Capt. Alexander 

 McDougall is the designer of what are known 

 as whale-shaped freight carriers, a considerable 

 number of which are already in service on the 

 lakes. He has lately constructed a tow steamer 

 especially designed for handling these barges. 

 She is similarly shaped and carries a powerful 

 engine, and it is estimated that in fair weather 

 she can tow as many as 100 of the barges referred 

 to. Should these expectations be sustained, this 

 may revolutionize the coal and iron-ore trade of 

 the lakes, since it would probably largely under- 

 bid the present steel and wood'en ships in this 

 line of business. 



The St. Clair River Tunnel. The enor- 

 mous increase of traffic -over the Grank Trunk 

 Railway, of Canada, and the connecting lines in 

 the United States, made it obvious several years 

 since that other means of transit than a steam- 

 car ferry were necessary across St. Clair river. 

 Surveys were made contemplating the construc- 

 tion of a bridge ; but, owing to the extreme flat- 

 ness of the country on both sides, this was found 

 impracticable, because of the great height neces- 

 sary to allow free navigation in the river. More- 

 over, the current is so swift (eight miles an hour, 

 at times,) that any possible structure in the na- 

 ture of a bridge would be liable to damage when 



ST. CLAIR RIVER TUNNEL. 



stern of the boat and empty the slip of ice in a 

 few minutes. A series of preliminary experi- 

 ments, comparing the efficiency of this new type 

 of boat with the old side-wheelers, gave results 

 favorable to the new type, both in consumption 

 of coal and in speed. An additional advantage 

 may perhaps be taken into account as suggested 

 in a paper read by Capt. Zalinsky before the Naval 

 Institute, in which he emphasizes the utility 

 of ferry boats for harbor defense, saying that 

 the pneumatic dynamite guns may be mounted 

 on them. Their light draught, great strength, 

 and good speed would render them very effective 

 for coast-wise operations. The wide, overhanging 

 guards would render it possible to introduce 

 armor of some kind, so that the boats could be 

 protected against torpedoes. The typical ferry 

 boat was used extensively during the civil war, 

 and proved highly efficacious for river service. 



Towing 1 Steamers. It is within compara- 

 tively few years that it has been discovered that 

 a steam engine of given power can do a great 

 deal more efficient work when set up in a tow 

 boat than when placed independently in a large 

 vessel. The development of towing has made 

 rapid progress in the Great Lakes of late years, 

 and tow barges of a new model have been intro- 

 duced, devoted mainly to the transportation of 



the ice broke up in the spring. At length the 

 construction of a tunnel was decided upon, to 

 cross the river from Port Huron, Mich., on the 

 American side, to Sarnia, on the Canadian side. 

 A company was formed in 1886, test borings 

 were taken on both sides of the river, and at- 

 tempts were made to begin the main tunnel by 

 sinking large preliminary shafts. These shafts 

 soon entered a stratum of soil that seemed to be a 

 mixture of clay and quicksand. It was so very 

 difficult of management, and the pressure on the 

 sides of the shafts was so tremendous, that at last 

 they had to be.abandoned and filled up with sand 

 in order to prevent dangerous subsidence of the 

 surface under adjacent buildings. Excavations 

 were then begun to approach the tunnel en- 

 trance by a gently inclined plane, and when a 

 sufficient depth was reached Beach hydraulic 

 shields were introduced, and the work proceeded 

 with remarkable dispatch. These shields were 

 designed by Alfred E. Beach, of the " Scientific 

 American," and patented in 1869. The first ex- 

 cavation was made under the steeets of New 

 York, with a view to an underground railway ; 

 but that design was abandoned, and only an ex- 

 perimental tunnel was constructed. The St. 

 Clair Tunnel has now so nearly approached 

 completion that it may be counted as one of the 



