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Over the years, several numbering systems have been employed by archivists to identify the notebooks used in the West Orange laboratory. Because these numbers frequently appear in published citations and in archival finding aids, they are included on the editorial targets appearing in the Notebook Series.
N-numbers. During the late 1930s archivists at the West Orange laboratory began assigning six-digit numbers, prefixed by the letter "N," to Edison's laboratory notebooks. Frequently this number corresponds to the first dated entry in the book. For example, a book whose first dated entry is from January 3, 1899, carries the number, N-99-01-03. Books with the same N-number are distinguished by an extension number (for example, N-01-07-01.1 and N-01-07-01.2). Although the N-number system was initially used only for standard-size (6" x 9") notebooks, archivists at the Edison National Historical Park (ENHP) have subsequently applied it to other notebooks as well.
N-numbers are not reliable indicators of the date on which a notebook was put into use. Some books were used for a long period before an entry was dated. Numerous other books contain no dated entries. Some of these undated books are indicated by the notation, "N-Undated," followed by an extension number (for example, N-Undated.35). For other undated books, a conjectured year serves as the first two digits of the N-number. For example, N-99-00-00.4 indicates one of four notebooks believed to date from the year 1899. Subsequent research has revealed that some of these conjectured years are inaccurate. Occasionally, an undated notebook bears an N-number indicating a conjectured day and month, as well as year. An example is N-01-04-16, which is a continuation of dated notebook N-01-04-15.
Not all of the standard-size notebooks and other N-numbered books appear in the Notebook Series. For example, several notebooks that were used for ore exploration, ore surveys, drilling reports, and plant operations can be found in the Edison Portland Cement Co. Records (Company Records Series). Among the items in the Laboratory Records Series are several standard-size notebooks containing project numbers and descriptive names for each laboratory project. A few standard-size notebooks do not bear N-numbers.
PN-numbers. These archival numbers are most often used to designate pocket-sized notebooks that generally measure about 3" or 4" in one direction and 6" or 7" in the other. As with the N-numbered notebooks, the six-digit number frequently corresponds to the first dated entry in the book. Undated books are designated either by the notation "PN-Undated" or by a conjectured year.
E-numbers. Until 1971 documents processed into the ENHP collections were often assigned a sequential accession number prefixed by the letter "E." These numbers appear most often on notebooks, scrapbooks, and other bound items, although they were occasionally used for batches of unbound documents.
The books in the "Notebooks by Edison" and the "Pocket Notebooks" subseries are arranged in chronological order according to the earliest date in the book, with undated books attributed by the editors to a particular year appearing after the dated books for that year. The books in the "Notebooks by Edison and Other Experimenters" subseries are arranged in ten groups, while the books in the "Notebooks by Other Experimenters" subseries are arranged in eight groups. For those groups consisting of sequentially numbered volumes or experiments, the individual books are arranged in volume or experiment order. The selected books in the other groups are arranged in chronological order according to the earliest date in the book; unselected books are listed on the targets in N-number order. The selected ore assay books in Group 10 of the "Notebooks by Edison and Other Experimenters" subseries, all of which are undated, are also presented in N-number order. The ten selected books in the "Miscellaneous Notebooks" subseries are arranged in chronological order.
Unbound notes and drawings are organized into folders by year. Within each folder, the dated items appear chronologically, followed by undated Edison material plausibly attributed to that year and then by undated non-Edison material. Following these folders is a folder of undated notes and drawings that cannot be attributed to a particular year and a folder of oversize material too large to be reproduced at the standard reduction ratio of 14:1.
Laboratory notebooks and unbound notes and drawings are indexed according to dated entries, as are notebooks and unbound notes and drawings in the Patent Series and Company Records Series. In the case of contiguous entries of the same date, the entry refers only to the first appearance of that date.
For the notebooks, the record refers to the page on which the date appears and not necessarily to the first page of the entry. The entries are of varying lengths, since some books contain numerous dates whereas others have only a few. There are also many notebooks with no dated entries; these books appear in the index under a conjectured year or range of years. In addition, some notebooks contain dated notations that were added by Edison, his laboratory assistants, or his patent attorneys after the initial entries were created. An example is Miscellaneous Notebook, E-4296, which covers the period March 1902-February 1903 but includes a few additional notations made by Edison in 1919. Because of the complex character of this material, researchers are advised to examine the pages preceding and following each indexed notebook page.
Notebooks containing daily (or almost daily) entries recording the results of repeated and repetitive testing are not individually indexed. Instead, an entry appears in the index for each month represented in the notebook. Examples include the storage battery endurance test books constituting group 2 of "Notebooks by Experimenters Other than Edison."