Parry was appointed President of the Edinburgh Medical Society, and helped to procure its Royal Charter.

In October 1816, Parry suffered a stroke, which paralyzed the right side of his body and impaired his speech.

Parry dedicated the work to Lord Bathurst of Cirencester, a close friend of his father.

Parry also devoted attention to the improvement of agriculture and studied the subject on a farm he had acquired near Bath.

He wrote in 1800 a tract on The Practicability and Advantage of producing in the British Isles Clothing-wool equal to that of Spain, and in 1807 an Essay on the Merino Breed of Sheep, which obtained a prize from the Board of Agriculture.

Parry's papers appeared in the Transactions of the Bath and West of England Society of Agriculture, from 1786 onwards, and in the Farmers' Journal for 1812.