Rees (251) explains the term as follows:
“Mechanics” were not technicians but simply labourers at or near the very bottom of the social scale. The institutes … were charitable establishments where these people were taught to read and write and where the rudiments of Victorian education were instilled. A variety of penny publications was brought out weekly by several organisations dedicated to the purpose, and there were of course the “penny readings.” Alexis’ speech commencing with “I hope so …” is a parody of the wide range of subject matter offered in these places to largely uneducated and frequently illiterate audiences. It is really all a matter of terminology: Bottom the weaver and his companions in A Midsummer Night’s Dream, a carpenter, a joiner, a bellows-mender, a tinker, and a tailor, were all “mechanicals.”
George Grossmith, the original D’Oyly Carte comic baritone, started his career as an entertainer in mechanics’ institutes. In his autobiography (146) he offers a good description of them. Bosdêt (43) adds that the institutes were established with funds donated by Queen Adelaide, wife of William IV (who reigned from 1830 to 1837).