This fascinating little oil painting by celebrated Scottish engineer, astronomer and artist James Nasmyth (1808-1890) depicts an 18th-century gentleman absorbed in a book.

Seated heavily in an upholstered armchair, he rests his forehead against one hand while the other lies across the open pages. His pale coat, waistcoat, stockings and powdered wig catch the light against a deep olive-green interior.

Around him is the private world of an educated man. A landscape painting hangs above a miniature portrait, while a handsome chest supports a candlestick, glass vessels and various objects. At his side stands a small table with further glassware, and a large portfolio leans casually against the chair. The room is quiet enough that one can almost imagine the ticking of a clock somewhere beyond the picture.

The composition appears to have been inspired by the celebrated French painter Jean-Louis-Ernest Meissonier (1815-1891), whose small historical interiors featuring solitary readers were enormously admired during the 19th century.

Born into a remarkable family of Scottish artists, Nasmyth was taught to draw by his father, the landscape painter Alexander Nasmyth. His elder brother Patrick became a successful professional landscape painter, while James chose engineering and ultimately became famous for inventions including the steam hammer.

But drawing and painting never disappeared from his life. Nasmyth believed that drawing was a form of thought. He described it as being "as familiar to me as language" and used it continually - to record landscapes, explain machinery, reconstruct geological ideas and eventually visualise the mountains and craters of the Moon.

He also possessed a lively antiquarian imagination. During quieter evenings he produced elaborate drawings of old castles, alchemists, antiquaries and fictional interiors, often placing solitary figures within imagined historical worlds. The Reader belongs naturally to that side of him.

Painted on 10 April 1874, it dates from an extraordinary period in Nasmyth's life. He had long since retired from commercial engineering and was devoting himself to drawing, photography, astronomy and scientific experimentation. The same year saw the publication of his celebrated study The Moon: Considered as a Planet, a World, and a Satellite, produced with James Carpenter.

Nasmyth spent his life studying how things worked - here, however, the machinery is entirely internal. A man sits in a chair with a book - and thinks.

On the reverse, he's included a coloured illustration of his steam hammer as a pictorial monogram. It's also signed, titled and dated on the reverse. Held in a later frame.

Read our essay: James Nasmyth, The Engineer Who Never Stopped Drawing.