4 ANNUAL OF SCIENTIFIC DISCO VICKY. 



very slight angle, and the bevelled parts lapped over each other, and 

 attached with glue. These joinings are so arranged that only one of 

 them ever occurs in the same cros^ section of the bridge, and they are 

 neither bolted nor clamped, but depend entirely upon the glue for their 

 adhesion. Each of these stringers has about nine feet bearing on the 

 abutments, to which they are firmly attached by iron bolts. 



SUSPENSION BRIDGE AT NASHVILLE. 



THE suspension bridge recently erected across the Cumberland 

 River at Nashville, Tenn., is, according to the Nashville Whig, 672 

 feet long. The other dimensions are as follows : Distance between 

 the towers, 538 feet ; width of superstructure, 28 feet ; base of pier, 

 60 by 30 feet; height above low water, 110 feet. There are 16 

 cables, each composed of 200 strands of No. 10 wire. The whole 

 work is calculated to bear a we*ght of 2,400 tons. 



ARCH-GIRDER. 



MR. JOHN BEVAN, of New York, has invented a " patent arch- 

 girder for bridges, roofs of buildings," &c. As applied to bridges, 

 it consists of a curved beam or girder, formed of two beams bolted to- 

 gether, with blocks between to keep open a space. Each beam is com- 

 posed of leaves or plates of wood or metal of convenient length ; these 

 are firmly secured to each other, the outer layer of plates breaking 

 joints with the inner layer. At the ends of the girder are fastened 

 cramp-iron pedestals, in which pulleys work. On the top of the girder 

 are also pulleys at short intervals. A wire rope passes over the girder, 

 resting on the pulleys, is brought over those at the ends of the girder, 

 and secured at the centre of the arch by clamps and a right and left hand 

 screw. As the length of the rope is less than twice that of the girder, 

 the latter cannot be straightened unless the rope is first broken. The 

 recommendations of this bridge are its simplicity and lightness, the 

 length of span of which it is susceptible, and the ease with which 

 portions of it may be repaired without interrupting the use of the rest. 

 Scientific American, June 29. 



ROTARY ENGINE. 



MR. F. R. DELANO, superintendent of the Carondelet Mills at St. 

 Louis, writes to the Scientific American for October 26, that in De- 

 cember, 1849, he went to Tyrees Spring, Tenn., for the purpose of 

 examining a rotary engine, which had been in use there three years, 

 the invention of Mr. J. A. Stewart. It consists simply in having two 

 cog-wheels, running into each other, and so brought into contact with 

 the caps and end-plates as to render them air and steam tight, without 

 any packing. It is made entirely of cast-iron, except the pillow- 

 blocks, which are lined with Babbitt metal. The steam is admitted 

 from above, between the two cog-wheels, and is confined there by a 

 cap and two cheek-pieces, \vhich embrace the upper portion of the 



