Abstract :
The following paper is to be read at the 27th Annual Convention of the American Institute of Electrical Engineers in Jefferson, N. H., June 28–July 1, 1910. This paper is to be presented under the auspices of the Railway Committee of the Institute. All those connected with the Institute and desiring to take part in the discussion of this paper may do so by being present at the meeting; or, if this is not possible, by sending in a written contribution.
