and conditions, is regarded as true. In view of which I here subjoin a notice of certain discoveries, cut from the pages of "Appleton's Journal":—
"The proposition, that knowledge is progressive, is common- place, but it nevertheless has an inexhaustible meaning. It implies successive conquests of the unknown, light behind and darkness before, and each age engaged with the definite work to which the past age has brought it, and which must be accomplished before future questions can be reached or future victories made possible. The intellectual work of an age is far from being what that age chooses. Past results are data; past effort is training; past experience, a preparation for researches which stand next in the logic of Nature's intellectual order. The historic epochs of inquiry are in definite sequence and intimate dependence.
"In the sixteenth century men first groped round the planet, and, grasping the conception of its form, dimensions, and of people on the other side, began to form definite notions of the world they lived in. This prepared for the work of the seventeenth century, which was, to ascertain the relations of the planet to the universe, and to determine the laws of motion in the heavens and on the earth, by which the foundations of physical science were laid. From the aspect of the universe in its vastness, and the properties of masses of matter, the eighteenth century passed to the study of nature in the opposite extreme of minuteness,—to the inner constitution and composition of material things, and the establishment of the science of chemistry. The discipline and results of physical inquiry, the art of experimenting, and the slow perfection of implements of research, were preliminary to the more subtile and refined investigation into atomic and molecular phenomena.
"With this scientific apprenticeship of three hundred years, the nineteenth century passes on, and enters upon the investigation of the great problem of life. The pioneering minds of the world are now absorbed in biological inquiries. Columbus before Newton, Newton before Lavoisier, and Lavoisier before Cuvier, Liebig, and Darwin, symbolize the sequence of discovery and indicate the problems that predominate in our own time. While physical and chemical inquiries are still pursued with greater intensity than ever, they have opened the gates of a still loftier research into
