In March 1788 he became assistant to Adair Crawford at the Royal Military Academy, Woolwich, at a salary of £30 a year.

[9] Some authors credit Cruickshank with first suspecting an unknown substance in a Scottish mineral, strontianite, found near Strontian, in Argyleshire.

Other authors name Adair Crawford for the discovery of this new earth, due to the mineral's property of imparting a redding color to a flame.

[13] Circa 1800, Cruickshank invented the Trough battery, an improvement on Alessandro Volta's voltaic pile.

[14] Shortly after learning of Alessandro Volta's discovery of the Voltaic Pile in 1800, Cruickshank conducted a number of experiments involving electrolysis.