DSC00620 (3)

39. Historlcal Nole. The fint movable nil frog w* taed in the trnck of the Killingworth nflway (an carly coal-carrying road in.the Newcastle distriet in Engłand). Thb was designed and madę by Mr. Nicholas Wood. Mcm. Insi. C. E., and was worked by a weight It was docribcd in the eecond edition of his book, "Practical Tmtisc on Raił-roads," publiabed in 1831. In the third edition of the aune book, pabiahed in 1838, he dwcribed a double spring raił frog of his design, illustrating it by a Steel engraring, which beari a marked rcsemblance to the drawing of a modern spring raił frog. Mr. Wood termed the frog a “form of Crossing," the word "frog," at thst time, not having been ippłied to raił crommgs.