Tube Extensometer: a special multiple extensometer for measuring the shrinkage and adhesion stresses between concrete and steel. The instrument was acquired in a red box file together with a box of glass plates and container for the extensometer.
The instrument was developed by W.H. (Sir William) Glanville FRS and described in Building Research Note No. 282 (Nov. 1929) and summarised in “Journal of Scientific Instruments” Vol. 6, no. 1:7-10 (Jan. 1929). The abstrct for the paper says:
In place of the steel bar normally used in adhesion testing the instrument makes use of a steel tube, thus enabling points of reference to be fixed internally. Strains are measured by the rotation of rollers to which small mirrors are attached. The form of the load distributions, due to the shrinkage of the concrete and to the pulling out of the tube in a testing machine, is given for two typical cases.
The associated box of smoked glass plates may or may not be associated with this instrument. A Post-it note attacheed to the box has the manuscript text “Used smoked glass ‘charts’ from vibrograph”.