Armstrong was a physician. He published many prose and poetical miscellanies, though none of them display either the fire of genius or the elevation of pure moral sentiment, and his literary fame rests almost exclusively upon his Art of Preserving Health.
This poem has given him deserved celebrity. He is original, both in the choice of his subject and the manner of treating it. His moral associations are dignified and sometimes sublime, and his versification, though it wants strength and nervous harmony, is yet free from harshness, and is uniform in its flow.
"On the whole," says Campbell, "he is likely to be remembered as a poet of judicious thoughts and correct expression; and, as far as the rarely successful application of verse to subjects of science can be admired, an additional merit must be ascribed to the hand, which has reared poetical flowers on the dry and difficult ground of philosophy."