No coin nor oath required. For personal study only.
A. b." of the Seetio~'s Classification.)
This conduit is constructed of highly glazed terra cotta, in sections two feet in length, with a tap joint on tile top and ends, and is bedded on a cast iron or terra eotta base plate.
Its interior is fitted with iron frames, placed at suitable distances apart, which clamp large plates of some suitable insulating material, such as glass. If bare wires be used, they may be drawn directly through the holes, but where insulated wires are employed, the openings should be fitted with short sleeves of porcelain or glass, to prevent the insulation being injured.
Some of the sections are fitted with tubular prq}ections for tapping the wires, wherever required, for house-t0-house supply.
Cast iron manholes are placed at suitable intervals. The slack of the wires is taken up every fifteen feet, and the wires are then clamped.
All the joints are carefully cemented in order to exclude moisture. It is stated that about one hundred yards of this system has been under trial in Fourth street, Camden, N. J., and that the cost will not exceed one dollar per foot run.
No provision is made for overcoming the effects of induction in telephone wires. After the duct has been laid and filled with wires, no addition or alteration to the wires can be made without laying open the street down to the level of the base of the conduit and remaking all the joints.
๐ SIMILAR VOLUMES
Graham Bell, a displaced Scotsman and professor of vocal physiology at Boston University, was not trying to invent the telephone. He was trying to teach deaf people to hear. His experiments involving the transmission of sound by electricity failed to accomplish his lifelong goal-a hearing prosthesis
Book Notices. 469 a thorough knowledge of the elementary portion of the subject with a brief account of the principal rocks and a ready method for their determination." To do this, it combines, to a large extent, the definitions as given in Lawrence's Co/ta (" Rocks Classified and Described"), with