primary forms of distribution were hard-copy books or published tables, the sole source was obvious—the printed pages generated at NNDC. When on-line access to the databases became available in the mid-1980s, the files had to be mirrored for easier access overseas. With the advent of the World Wide Web, individuals gained the ability to manipulate the databases, which today still reside at NNDC, using overlay programs that (physically) reside at another data center, possibly in Europe.
In the future the user probably will be unaware of where the data file being accessed physically resides and will be able to link to the journal article (published by a commercial publisher, for example) in which the data originally appeared. The electronic journal article could have links to the original data tables of the authors. NNDC has evolved from a collector of evaluated data files, which were formatted into camera-ready pages for hard-copy publication, to a center that maintains on-line access to a few databases via a variety of overlay programs (no longer is there a single, static format). It is one of many centers around the world, now common in most scientific disciplines, that develops new, electronic forms of networked data dissemination.
The development and acceptance of electronic networks as a means of communicating, searching for data and information, and accessing information rapidly and directly have driven the increase in electronic publications of all types, and scientific publications in particular. 20 Although not all publishers of scientific journals are moving to completely electronic form, there is a distinct trend to provide alternative paper and electronic versions of many publications. For example, the American Institute of Physics is working to provide its library clients by early 1997 with electronic access to every one of its journals to which the library subscribes. In addition, it now offers some of its journals in CD-ROM form as a space-saving alternative or supplement to its subscribers.21 The Institute of Physics in the United Kingdom also provides subscribers with electronic access to all 33 of its journals.22
NASA is sponsoring an all-electronic peer-reviewed journal, Earth Interactions.23 It is only available electronically and allows color representations of phenomena, including time-lapsed video clips of observations to show time variations. Mathematical calculations on subsets of original data can be carried out by the reader as well, providing both in-depth understanding of the material and a check on the validity of the author's results. This new journal is the product of three professional societies—the American Meteorological Society, the American Geophysical Union, and the Association of American Geographers—with additional support from the Ecological Society of America and the Oceanographic Society of America. These societies have a combined membership of approximately 45,000, and so this form of electronic publication will soon be