Did engineers like I.K. Brunel and his contemporaries employ calculus in their constructions? Or did they work just with 'rules of the thumb' and useful 'laws' like the square-cube...? What was the level of maths (beyond simple algebra and trigonometry) used by engineers in those times?
Augustin-Louis Cauchy (1789-1857) graduated in civil engineering and in 1816 was appointed professor at École Polytechnique.
The seminal Cours d'Analyse was published by Cauchy in 1821 as Cours d'Analyse de l’École Royale Polytechnique.
On this ground, we have to presume that the calculus was part of Brunel's professional knowledge.