British naval surgeon who worked at the Naval Hospital in Chatham and travelled to South Africa, the Comoro Islands and India. He corresponded with academics including Sir Hans Sloane and sent plants to a number of contemporary botanists including L. Plukenet and S. Doody. Sloane acquired the herbaria of Doody and Plukenet and these were subsequently bequeathed as part of the founding collections of the British Museum in 1753. The familiar horticultural plant Stag's Horn Fern (Platycerium alcicorne (Sw.) Desv.) is based on a specimen of Adair at BM-SL (H.S. 102, f. 194) from the Comoros.