of the University of Cambridge, and to Snow Harris, Esq., of Plymouth, for obliging replies to questions proposed to them. Likewise, acknowledgment is willingly made of the readiness with which Mr. E. Palmer, of 103, Newgate Street, afforded the use of his diagrams, and permission to draw from original instruments. From these sources, from the best treatises, as well as from experiments in hours of recreation, the author has derived his facts and illustrations; and he has much gratification in committing them to a Society whose rules demand a religious application, consonant with those spiritual truths of the gospel, the dissemination of which forms the primary design of all its publications.