His lectures, delivered gratuitously at Torquay, were very popular, and were attended by large audiences. The fame of them spread, and he was called to other places--Exeter, Exmouth, and larger towns and farther off, and to the great learned societies--where he lectured, always with success, and to the satisfaction and delight of his audiences. "Those persons living, and they are many," says Mr. F. S. Ellis in the preface to Hester Pengelly's biography of her father, "who had the good fortune to hear Pengelly lecture will bear ready witness to the complete mastery he always had of his subject, and of the faculty of imparting his knowledge. Even when speaking upon abstruse subjects to a mixed audience, he would make the matter perfectly clear without in any degree appearing to talk down to the capacity of those he was addressing.... His manner was no less pleasing and attractive than the language in which he clothed his ideas was grateful to the ear." Geology and astronomy furnished the subjects of the lectures. It would be impracticable in a brief sketch to follow the detail of Pengelly's geological investigations previous to his engaging in systematic cave exploration. They embraced fields chiefly in Devonshire and Cornwall, and afforded subjects for correspondence and discussion with many of the most eminent British geologists, and some of other countries than England. A study of some fossil fish, first observed by Mr. Charles W. Peach in Cornwall, furnished the occasion for one of his first recorded papers, On the Ichthyolites of East Cornwall, in the Transactions of the Royal Geological Society of East Cornwall, 1849-'50; and a single volume--the seventh--of these Transactions contains nine of his papers. Another subject of interest was the beekites, curious formations of chalcedonic silica on the limestone fragments in the New Red Sandstone of Devonshire, first observed by Dr. Beek, of Bristol, concerning which he read a paper at the Cheltenham meeting of the British Association, the first which he attended, in 1856. In 1860 he completed the formation of a collection of Devonian fossils from Devon and Cornwall, which was presented by the Baroness Burdett-Coutts to the new museum of the University of Oxford, in connection with the foundation of a geological scholarship, and was named "the Pengelly Collection."