Emily Dickinson Lexicon

THER-MO-TEN'SION, n. [Gr. θερμος, hot, and L. tensio, a stretching.]

Literally, a stretching by heat. This word is applied by Professor Johnson, to a process of increasing the direct cohesion of wrought iron. It consists in heating the metal to a determinate temperature, generally from 500 to 600 degrees of Fahrenheit, and in that state, giving to it, by appropriate machinery, a mechanical strain or tension in the direction in which the strength is afterward to be exerted. The degree of tensile force applied is determined beforehand by trials on the same quality of metal at ordinary atmospheric temperature, to ascertain what force would, in that case, have been sufficient to break the piece which is to be submitted to thermotension. If this process should succeed, it may be of great use in giving strength to chain cables.