Troy, N.Y. W. & L. E. Gurley 1899. Cloth folder 6 5/8 x 6 1/2 inches. Gilt titling. Some wear to the central fold, with some separation starting head and tail. Still sound and usable. Inside front shows great illustration of a Gurley surveying instrument with some nice advertising copy. Inside rear has a volvelle (circular slide rule) in paper with brass grommet and brass movement ring. Inside ring is labeled Difference of Elevation. Soiling from use. Very Good. 
A wonderfully graphic example of a working surveyor's tool. Includes directions for use. While at first glance 1899 might seem early for the use of the term "computer" applied to an object instead of a person, the term was first used on a volvelle by Aaron Palmer in 1843. Gurley is recognized as one of the most successful surveying instrument makers in the United States. Their instruments and related material are avidly collected by those interested in the "pre-digital" age of surveying.
Stadia is a method of surveying in which distances are read by noting the interval on a graduated rod intercepted by two parallel cross hairs (stadia hairs or stadia wires) mounted in the telescope of a surveying instrument, the rod being placed at one end of the distance to be measured and the surveying instrument at the other. (dictionarycom)
Not often found in the marketplace. Four listings in OCLC as of this writing.