increasing in a geometric ratio. To take a single instance; the Astronomische Nachrichten established about 1825, now the oldest and most reputable astronomical journal of the world, began by supplying practically all the needs of astronomers for a medium of communication, by issuing perhaps one volume in a year. With every decade the number of volumes went on increasing until, in recent years, three or four volumes have been issued annually, and the one hundred and seventieth volume is soon to appear. But this is not all. Even with this continually increasing number, the publication has fallen short of the requirements of astronomical investigators, so that fresh media of communication have from time to time been opened. New scientific societies including astronomy, and new astronomical societies, are from time to time founded. The American Astronomical Journal founded by Dr. Gould in 1849, and revived in 1885, takes the place of the Astronomische Nachrichten in this country. The Monthly Notices of the Royal Astronomical Society have continually grown until the annual volume has become of alarming thickness. New astronomical societies add to the mass, and as if these were not sufficient, several great observatories have commenced series of their own. The result is that an astronomer can hardly know more than a small fraction of what is being done in his own field, and, if an attempt were made to subdivide this science into its minutest specialties, one would hardly know where to stop.
What is true of astronomy is true not only of all the older sciences, but of the new ones, which are from time to time being opened up, and of the various specialties into which every branch of science is divided. Dictionaries can not keep pace with the new -ologies, -ographies and -onomies,—and he is a scholar indeed who, on hearing the name of any science, could on the moment accurately define its field. Depressing indeed would be the prospect if scientific investigators could look forward only to an unending increase of this process of subdivision. When the number of serials becomes so great that a mere catalogue of them makes a book, as is now the case, and when the volumes of a serial mount up into the thousands, as they must before many generations pass, who shall be able to know what is contained in them? Most happily, we can see the possibility of an opposite process—the addition of integration to the indefinite differentiation with which we are so familiar. As we go deeper into all the laws of nature, we are led nearer and nearer to the belief that the fundamental principles on which her operations are carried on may be few in number, and that what seems to us a great diversity of laws may consist in the action of one and the same law under a variety of different conditions. It is true that the process of reducing all natural operations, even those of inanimate nature, to their first principles, is