The manuals published by W. & L.E. Gurley, one of America's leading producers of mathematical and scientific instruments, have been used by generations of engineers and surveyors. In this manual Gurley describes all of its various instruments: how they are calibrated, used and maintained. The remainder of the book is devoted to a catalog of the instruments being offered. The 1874 edition is especially valuable since it is one of the earliest complete catalogs and rarely found in the original. With an introduction by David C.Garcelon. 256 pages................ sale ... $17.00