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The same thing applies to the bar scale(s) on nautical charts. On some of the earlier charts (i.e. 19th c), as many as three such scales are shown: Statute Miles, Nautical Miles, and Scale of yards. In the first two instances, the gradations to the right of the zero are out to "5" and the gradations to the left of "0" are divided into four parts. By placing a pair of navigator's "dividers" onto the scale either side of "0", it is then an easy matter to transfer that information to a plotted course line or "whatever" (like the nearest rock so as to avoid going aground). Fair winds and following seas, Charles -----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Bill Warren Sent: Tuesday, August 25, 2009 6:50 PM To: Discussion group for map history Subject: Re: [MapHist] Bar Scale Data ? I would agree with Francis. It is quite common for a scale bar to read to the right of zero in units of, say, ten. Then to the left of zero will be a ten space exactly equal in length to the ten space to the right, but calibrated in units of one. Hence if you wish to find exactly 14 miles one would make a tick on a piece of paper laid next to the scale at the ten mile mark to the right and a similar tick four units (miles) to the left of zero. You now have a measuring device you can lay on the map to determine exactly 14 miles. The units are immaterial, they could be miles, kilometers, leagues, whatever, the process is unitless. Bill Warren, who plays with maps at the Huntington Library 1109 Linda Glen Drive Pasadena, CA 91105 (626) 792-9152 [email protected] ---------------------------------------------------------------------------- -- From: Vladimiro Valerio <[email protected]> To: Discussion group for map history <[email protected]> Sent: Tuesday, August 25, 2009 3:35:33 PM Subject: Re: [MapHist] Bar Scale Data ? This is a MapHist list message (when you hit 'reply' you're replying to the whole list) o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + Very good, Francis, It is just whst I too suspected but, a great BUT, Kin Edwin wrote: "This interval to the left of 0 is also the same distance as those intervals on the right side of the 0." This description doesn't apply to your (my) hypothesis. May Kim send us an image? vladimiro Il giorno 25/ago/09, alle ore 20:00, Francis Herbert ha scritto: > This is a MapHist list message (when you hit 'reply' you're replying to the whole list) > o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + o + > > I suspect that you are describing a fairly common feature of many > graphic map scale-bars in whatever measures. The extending of the bar to > the left of the '0' is usually made to supply more detailed > marked/ticked sub-divisions to those fewer and general ticked scale-bar > divisions to the right (and/or vice-versa). Thus, if the left-hand > extension is in individual unit ticks of 1 (up to 10) miles it > facilitates the calculation of 'abnormal' mileage distances - such as > even-numbered 12 or 16 miles - when combined by reading off the > right-hand generalized distances (if, e.g., they are multiples of > odd-numbered 5-mile unit ticks). Not so easy to explain over the > internet; but find a text book or manual on map-reading - or even Ed > Redmond . . .:) > > Francis Herbert (former curator of maps somewhere) > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Kim H. Edwin > Sent: 25 August 2009 17:48 > To: [email protected] > Subject: [MapHist] Bar Scale Data ? > > Dear Mapsters, > > While working on some Pictorial Maps, I found a couple from the 1940's > which have bar scales extended left of the traditional 0 distance. This > interval to the left of 0 is also the same distance as those intervals > on the right side of the 0. > > Would someone please let me know what this is called and why it is done? > > Kim Edwin, Library Technician > Library of Congress, Geography & Map Division > 202-707-6277 > > _______________________________________________ > MapHist: E-mail discussion group on the history of cartography > hosted by the Faculty of Geosciences, University of Utrecht. > The statements and opinions expressed in this message are those of > the author and do not necessarily reflect those of the University of > Utrecht. The University of Utrecht does not take any responsibility for > the views of the author. > List Information: http://www.maphist.nl > > Maphist mailing list > [email protected] > http://mailman.geo.uu.nl/mailman/listinfo/maphist _______________________________________________ MapHist: E-mail discussion group on the history of cartography hosted by the Faculty of Geosciences, University of Utrecht. The statements and opinions expressed in this message are those of the author and do not necessarily reflect those of the University of Utrecht. The University of Utrecht does not take any responsibility for the views of the author. List Information: http://www.maphist.nl Maphist mailing list [email protected] http://mailman.geo.uu.nl/mailman/listinfo/maphist
_______________________________________________ MapHist: E-mail discussion group on the history of cartography hosted by the Faculty of Geosciences, University of Utrecht. The statements and opinions expressed in this message are those of the author and do not necessarily reflect those of the University of Utrecht. The University of Utrecht does not take any responsibility for the views of the author. List Information: http://www.maphist.nl Maphist mailing list [email protected] http://mailman.geo.uu.nl/mailman/listinfo/maphist
