SECTION III., 1901 [3] Trans. R, $. C. 
IA New Extensometer. 
By Henry T. Bovey, M.Inst. C.E., F.R.S.C., Etc. 
(Read May 22, 1901.) 
The purpose of the present paper is to describe a new extensometer, 
which has been designed with the object of determining the amount of 
the longitudinal extension or compression of any given length, parallel 
to the axis, in a horizontal beam loaded transversely. 
SPEGIMEN 

Fig. B. 
The device by which the actual deformation is measured consists 
of a small mirror, suitably mounted on a roller, which is held between 
the faces of two overlapping longitudinal steel bars (Fig. A). These bars 
are designed to have a capacity of 8 to 12 inches in length. Each bar is 
slotted nearly the entire length and, at one end, is bent at right angles 
and passes into the slot of the companion bar. At its other end, each 
bar is also slotted transversely, and pass over pivotted knife edge 
terminals, held in the desired positions on the face of the specimen, by 
means of spring fingers. Any extension or compression of the specimen 
between these knife edge points produces a corresponding movement 
of the bars, thus causing the partial rotation of the mirror, and so 
