KEY. CHESTER DEWEY, D. D., LL. D, LATE PEOFESSOK OF CHEMISTRY AND NATURAL PHILOSOPHY IN WILLIAMS COLLEGE. Sir : As one of the earliest Teachers of Geology and Natural History in this country, as a lover and successful cultivator of these departments of learn ing, as one of high scientific attainments and moral worth, and especially as a friend, the author feels that you deserve a higher testimonal of his regards than the dedication of this work; still, he hopes that it may be received as a mark of esteem, and an ex pression of his appreciation of your kindness and friendship continued through many years. Albany, Sept. 20th, 1855.