Pengelly was one of the prime movers and a leading spirit in the organization, in 1862, of the Devonshire Association for the Advancement of Science, Literature, and Art, at Plymouth, and was its president in 1867-'68. The objects of the association were "to give a stronger impulse and a more systematic direction to scientific inquiry in Devonshire, and to promote the intercourse of those who cultivate science, literature, or art in different parts of the country." It worked according to the methods of the British Association, with literature and art added to its objects, besides giving some attention to history and archæology. The first meeting was held under the presidency of Sir John Bowring. In 1872 the president was the bishop of the diocese, Dr. Temple, now Archbishop of Canterbury. In 1863 Pengelly was elected a Fellow of the Royal Society. From 1856, when he read a paper at the Cheltenham meeting, Mr. Pengelly was almost a constant attendant upon the meetings of the British Association, and gained, as the years advanced, a prominent position among its leading members. He was president of the Geological Section at the Plymouth meeting, 1877. At the jubilee meeting of the association, held at York in 1880, he made the acquaintance of Prof. Asa Gray, which ripened into a friendship and resulted in a visit of Professor Gray and Mrs. Gray to Torquay. He met another distinguished American man of science, Prof. O. C. Marsh, recently deceased, at the International Geological Congress in London, in 1888. In 1801 he received a visit from Prof. G. F. Wright. He opposed the transference of the meeting of the British Association to Montreal in 1884, on account of the expense and the sacrifice of time which he thought many who would like to attend could not afford, and did not go himself. In March, 1874, he was visited at Torquay by Professor Phillips and others in behalf of a number of members of the British Association, and presented with an illuminated parchment containing the signatures of the contributors and a check, as a testimonial "in recognition of his long and valued services to science in general, and more especially for the exploration of Kent's Cavern. Replying to the addresses, he said he had done the work in connection with Kent's Cavern simply because he liked it.... He had experienced intense pleasure in it, and he could assure them that, on his finding a _Machairodus latidus_, after seven years and a half exploration, the discovery of that one tooth, in his opinion, was worth all the money that had been spent in the exploration of the cavern." Besides geology, Mr. Pengelly had a living concern with astronomy, on subjects of which he lectured and read papers, and in folklore, and was "extremely interested" in the religious history of Cornwall. He became a member of the Society of Friends about 1853, and married his second wife, Lydia Spriggs, in that body. She assisted him in his scientific work, preparing diagrams.