in advance with the theodolite.  No time is lost; as in chaining, since the marks may be made wherever and as often as convenient.  In work where high accuracy is required this instrument is well adapted for filling in, and where a rough idea of the nature of a given curve is required, the mirror being adjusted for any three points upon it, the various elements may be read off on the scales.  A telescope is provided, but the errors not being cumulative, it is rarely required.  The curve ranger weighs 1 lb. 10 oz., and is manufactured by Messrs. Elliott Bros., St. Martin’s Lane, London.  It is the invention of Mr. Alex.  P. Trotter, Westminster.—­The Engineer.

* * * * *

THE RAIL SPIKE AND THE LOCOMOTIVE.[1]

  [Footnote 1:  Abstract from the History of the Camden and Amboy
  Railroad.  By J. Elfreth Watkins, of the National Museum,
  Washington, D.C.]

Early in October, 1830, and shortly after the surveys of the Camden and Amboy Railroad were completed, Robert L. Stevens (born 1787) sailed for England, with instructions to order a locomotive and rails for that road.

At that time no rolling mill in America was able to take a contract for rolling T rails.

Robert Stevens advocated the use of an all-iron rail in preference to the wooden rail or stone stringer plated with strap iron, then in use on one or two short American railroads.  At his suggestion, at the last meeting held before he sailed, after due discussion, the Board of Directors of the Camden and Amboy Railroad passed a special resolution authorizing him to obtain the rails he advocated.

ROBERT L. STEVENS INVENTS THE AMERICAN RAIL AND SPIKE.

During the voyage to Liverpool he whiled away the hours on shipboard by whittling thin wood into shapes of imaginary cross sections until he finally decided which one was best suited to the needs of the new road.

He was familiar with the Berkenshaw rail, with which the best English roads were then being laid, but he saw that, as it required an expensive chair to hold it in place, it was not adapted to our country, where metal workers were scarce and iron was dear.  He added the base to the T rail, dispensing with the chair.  He also designed the “hook-headed” spike (which is substantially the railroad spike of to-day) and the “iron tongue” (which has been developed into the fish bar), and the rivets (which have been replaced by the bolt and nut) to complete the joint.

A fac-simile of the letter[2] which he addressed to the English iron masters a short time after his arrival in London is preserved in the United States National Museum.  It contains a cross section, side elevation and ground plan of the rail for which he requested bids.

The base of the rail which he first proposed was to be wider where it was to be attached to the supports than in the intervening spaces.  This was afterward modified, so that the base was made the same width (three inches) throughout.