50 ANNUAL OF SCIENTIFIC DISCOVERY. 



Pan Handle Railroad, and reaches the face of the hill (which at 

 this point is 90 feet above the level of the Pan Handle Railroad 

 track) by means of an iron bridge 160 feet long. This bridge is 

 supported by 10-inch columns, made of wrought iron a quarter of 

 an inch thick. "The vertical height of the hill at this point is 330 

 feet, giving the plane a length of 650 feet, and an inclination of 



35 degrees. The roadway consists of 2 tracks, each 5-feet gauge, 

 with 2 cars, one ascending while the other descends. The 

 cross-ties on the iron bridge are yellow pine, 7 feet by 7 feet. 

 The stringers are also yellow pine, 6 by 8 feet, and the ties on the 

 balance of the track 8 feet by 8 feet. A pine railing runs from 

 the base to the top of the incline. It is 3 feet high, and quite 

 fancy. It is to be painted probably white. The rails are of 

 the " T " pattern, and substantially fastened to the stringers. 



The cars are to be hauled up by a wire rope, and are provided 

 with a safety-cable, which runs idly except in case of the breakage 

 of the principal rope, when the drum about which the safety- 

 cable winds is held by means of a brake, thus preventing the 

 accidental descent of a car. Scientific American. 



THE NEW TUNNEL UNDER THE THAMES. 



The new tunnel does not detract from the merits of Brunei's 

 great achievement in constructing the renowned passage between 

 Rotherhithe and Wapping, but it is as great a wonder in its way, 

 and in several respects offers a marked contrast. The old tunnel 

 brickwork is 38 feet wide by 22k feet high ; the new tunnel con- 

 sists of an iron tube about 8 feet diameter over all. The old tun- 

 nel was worked by a shield weighing 120 tons, accommodating 



36 workmen ; the new tunnel has been driven by a shield weigh- 

 ing 2 tons, and accommodating at most 3 workmen at a time. 

 The old tunnel was 5 times tilled by irruptions from the river; 

 in the construction of the new tunnel the water encountered 

 might at almost any time have been gathered in a stable pail. 

 18 years elapsed between the commencement and the completion 

 of the works in one case ; less than a year has sufficed for the 

 execution of the works in the other. The descending shafts of 

 the one were 84 feet deep and 50 feet diameter ; of the other they 

 are under 60 feet deep and 10 feet diameter. The cost of the one 

 was over 600,000 ; of the other it has been under 20,000. 



At the Tower Hill shaft we found the lift in which passengers 

 are to ascend and descend fitted and at work. It is an iron 

 chamber nearty cubical in shape, and large enough to accommo- 

 date 7 or 8 persons comfortably. The entrance is by a pair of 

 sliding doors. Guide-rods are attached to opposite sides of the 

 shaft, and corresponding grooved rollers are fixed to the sides of 

 the lift. The lift is balanced by a large cast-iron weight with an 

 open centre to admit of its being loaded in accordance with the 

 number of passengers that have to be raised or lowered. There 

 is a continuous connection above and below between the lift and 

 the balance weight by chains and wire ropes, calculated for 50 

 times the strain that can ever be put upon them. These pass 



