The bicron was a proposed unit of length = one billionth of a meter, which would be synonymous with the current SI unit the nanometer. The proposed prefix bicro-, meaning one billionth, would be synonymous with the current SI prefix nano-. These terms, together with bega-, trega-, quega- and trico-, were introduced in an 1894 article by Edwin J. Houston and A. E. Kennelly. Their entire article is reprinted below as source note 1.

At the time, the two men were partners in an electrical engineering consulting firm. Kennelly would later become a professor at both Harvard and M.I.T.; Houston would be twice elected President of the American Institute of Electrical Engineers. In other words, the article would not have been received as the work of cranks.

Houston was a prolific author whose work ranged far beyond the professional
treatise, including high school texts in geography and algebra, and such works
as *The Wonder Book of the Atmosphere*, *At School in the Cannibal
Islands* and *The Boy Electrician, or, The Secret Society of the Jolly
Philosophers*. Among his books was a very successful dictionary of
electric terms, which by 1898 was in its fourth
edition. In his dictionary he listed the bicro- :

**Bicro**.—A prefix for one billionth, one thousand millionth, or
10^{−9}.

**Bicro-Ampere.**—The billionth of an ampere.

**Bicro-Farad.**—The billionth of a farad.

**Bicro-Henry.**—The billionth of a henry.

**Bicron.**—A unit of length equal to the billionth of a metre, and
indicated by the symbol * μμ*.

Edwin J. Houston.

*A Dictionary of Electrical Words, Terms and Phrases*. Part two: T to Z.

New York: P. F. Collier and Son, 1903.

Appendix B, page 694.

From there it was picked up by later compliers of dictionaries:

μμ.—The double Greek letter (*mu*) corresponding to *m*, used as the
symbol for bicron, a unit of length.

...

Bicro.—A prefix often used with a physical unit to designate *one-billionth
part* of that unit.

N. [Nehemiah] Hawkins.

*Hawkins' Electrical Dictionary*.

New York: Theodore Audel and Company, 1915.

Aside from its appearance in dictionaries and the work of the proposers, we have
not found any of these prefixes in the scientific literature. (If any reader
encounters them, we would greatly appreciate an email with the citation.) By 1919, a writer in
the * Encyclopedia Americana* commented:

The names “bicron” and “tricon” have been proposed, respectively, for the billionth and trillionth part of a metre, but they have not been generally adopted, and probably will not be. Etymologically, at least, they are monstrosities.

*Encyclopedia Americana*, vol **19**, page 33, under headword micron.

New York: Encyclopedia Americana Corporation, 1919.

The bicro- and the other prefixes proposed by Houston and Kennelly are significant because they exemplify the pressure the work of “electricians” put on metrologists in the late 19th century to extend the metric system to ever smaller and larger units. “Mega-” is a survival of this effort.

1

Edwin J. Houston, Ph.D., and A. E. Kennelly.

On Certain New Prefixes Proposed for Physical Unit Magnitudes.

*The Electrical Engineer*, volume **17**, no 309, (April 4, 1894). Page
301.

**On Certain New Prefixes Proposed for Physical Unit
Magnitudes**.

The increasing extent to which scientific unit magnitudes are being used in physical research, has received a check by the inconvenient size of some of the fundamental C. G. S. units, particularly the dyne and the erg. In order to lessen this inconvenience, we would propose the following additional prefixes, which we have found convenient in our own work.

For example, instead of writing “one thousand megergs” we would suggest the term, one “begerg”; and, similarly, for the expression, “one million megergs,” the term “tregerg”; and for a billion megergs a “guegerg,” – following the analogy presented by the words million, billion, trillion and quadrillion.

Again, instead of writing, “the one thousandth of a microfarad,” we would suggest the use of the term “bicrofarad,” and also the “tricofarad” as the millionth of a microfarad where necessary.

The meaning of these suggested prefixes is, therefore, as follows:

Bega = 1000 million, or a billion, or 10⁹.

Trega = one million million, or a trillion, or 10¹².

Quega = 1000 trillion, or a quadrillion, or 10¹⁵.

Bicro = 1000 millionth, or 10⁻⁹.

Tricro = one trillionth, or 10⁻¹².

The following applications of these prefixes will suggest their advantages.

From | 1 metre | = | 1. | metre | = 100 cms. |

and | 1 mm. | = | 0.001 | " | = 0.1 cm. |

and | 1 micro-metre | = | 1. | micron | = 0.000,001 metre |

= 10⁻⁶ metre = 10⁻⁴ cm. | |||||

1 bicro-metre | = 1 bicron = | 0.000,000,001 | metre | = 10⁻⁹ metre | |

= 10⁻⁷ cm. | |||||

1 tricro-metre | = 1 tricron = | 0.000,000,000,001 | metre | = 10⁻¹² metre | |

= 10⁻¹⁰ cm. |

The micron is of the order of the length of a light wave in the ether, and is a fundamental unit of magnitude in microscopy.

The bicron is a magnitude which will be useful in dealing with the mean free path of gaseous molecules according to the kinetic theory of gases.

The tricron is of the order of atomic dimensions according to the estimate of Kelvin.

From | 1 megadyne | = 10⁶ | dynes | = approximately the earth's gravitational force on one kilogram of matter. |

1 begadyne | = 10⁹ | dynes | = roughly the earth's force on one ton of matter; i.e. the weight of one ton. | |

1 tregadyne | = 10¹² | dynes | = roughly the weight of one thousand tons. | |

1 megerg | = 10⁶ | ergs | = 0.0737 foot-pound at Greenwich. | |

1 begerg | = 10⁹ | ergs | = 73.7 foot-pounds at Greenwich. | |

1 tregerg | = 10¹² | ergs | = 73,730 foot-pounds at Greenwich = 37 foot-tons approximately | |

From | 1 megohm | = 10⁶ | ohms. | |

1 begohm | = 10⁹ | ohms | = 1000 megohms | |

1 tregohm | = 10¹² | ohms | = one million megohms. | |

1 quegohm | = 10¹⁵ | ohms | = one thousand tregohms. |

A begohm is about the insulation [*sic*] of one mile of well insulated conductor.

A tregohm is about the resistance required to limit the deflection of a high grade mirror galvanometer under one volt to one scale division of one millimetre at one
metre range. Such a galvanometer might be called a *tregohm galvanometer*.

A quegohm is the limiting resistance with one volt and unit deflection, of an extremely
sensitive mirror galvanometer, which might be termed a *quegohm galvanometer*.

From 1 microfarad = 10⁻⁶ farad.

1 bicrofarad = 10⁻⁹ farad or m. microfarad.

The C. G. S. electromagnetic unit of capacity being 10⁹ farads is consequently a begafarad. The use of these prefixes, therefore, assigns a convenient name to the C. G. S. unit of capacity which would otherwise require a special denomination.

From 1 henry = 10⁶ cms

and 1 microhenry = 10³ cms.

1 bicrohenry = 1 cm.

Laboratory of Houston and Kennelly,

Philadelphia, March 9, 1894.

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Last revised: 12 October 2009.