Clerk was an exceptional amateur artist. His wealthy background afforded him the luxury of entertaining numerous careers, including medicine and business, and he also showed a considerable interest in geology. In the 1740s he began sketching alongside his brother-in-law, Robert Adam, and the artist Paul Sandby. Clerk travelled extensively throughout Scotland, recording a wide range of landscapes and ancient buildings. His sketches of Edinburgh and the surrounding areas are highly personal representations of his native countryside. Clerk's youthful fascination with the sea and the navy resulted in his famous study 'An Essay on Naval Tactics' (1790), which he developed throughout the 1790s.