The Washington Meridian
or, the American Meridian
During a relatively brief period beginning in 1850, the "prime meridian" in the United States was not "the Prime Meridian" (i.e. the Greenwich Meridian), but rather the "American Meridian" (also known as the "Washington Meridian").
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Over the years I have made some effort to visit each of Colorado's corners, and along the way I have gleaned a bit about how the state's boundaries were defined and surveyed. So as I was preparing for a summer 2009 family trip to Washington DC, one of the places I was interested in visiting was the old Naval Observatory, since the boundaries of my state are defined in relation to this building. However, I soon learned that Bu-Med is unfortunately not open to the public**. Too bad... but I did receive something of a consolation prize: as my family was walking from the Arlington Cemetery to the Lincoln Memorial, I caught sight of a small white observatory dome off to the north. Conscious of what I was looking at, I took this photo...
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...and then, right there on the Arlington Bridge, I proceeded to give my family a brief lecture on the relationship of that building to the shape of our own state, hundreds of miles off beyond the western horizon. (Alas, it was received with rolling eyeballs and much less interest than I would've hoped.) Later on that same trip, we visited the American Meridian plaque, at the southeast corner of 24th and "H" streets:
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I have a few problems with the text of that plaque, foremost of which is the fact that all of the specified lines of longitude appear to be off by two degrees! Wyoming's east and west lines are actually 27 and 34 degrees, respectively; while Colorado's are 25 and 32 degrees. And I'm not sure Oregon's eastern border was really defined according to this meridian. In fact, I don't think any of California's or Washington's borders have anything to do with this meridian, either.
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On the sidewalk at the foot of that marker, a granite strip is inlaid among the bricks, engraved with the text "The American Meridian":
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The design of this small monument can lead one to believe that they are standing right on the actual meridian, but from what I observe on aerial photos, I am skeptical that is truly the case. Rather, it appears 24th St sits on the actual meridian. (Or, probably more accurately, the observatory was built upon the centerline of 24th Street's right-of-way, and thus 24th became the de facto meridian). Of course it wouldn't have been practical to put a marker in the middle of the street, so I imagine this site along the sidewalk was deemed to be close enough. But it has given rise to some dubious claims. For example, it has been stated that this Meridian bisects some of the buildings on the George Washington University campus. Well, 24th Street doesn't run through any buildings, so I don't think the Meridian does, either. I suspect these misconceptions can be traced back to the placement and design of this monument, and the way things are worded on the plaque.
Anyone who has had elementary-level geography should be familiar with the concept of the Prime Meridian, but it would seem far fewer people are aware of the fact that the U.S. once had a different "prime meridian" of its own. As we've seen, the position of this meridian was determined by the location of an observatory. Or, to put it another way, the meridian was not defined in relation to a whole-integer degree of longitude west of Greenwich. The American Meridian was about three arc-minutes away from 77 degrees west of Greenwich, which translates to nearly three miles. Chandler Robbins, the man who led the survey team that set the original Four Corners monument, anticipated the confusion that this offset might cause, so in a letter to the Santa Fe newspaper, he wrote the following about the west boundary of Colorado: "It seems to have been the general impression that the line was the 109 degrees of longitude west of Greenwich. Such is not the case, as the law makes it 32 degrees of longitude west from Washington, which corresponds to 109 degrees 02 minutes 59.25 seconds west from Greenwich, and which places the line a small fraction less than three miles farther west than would have been the case if it had been run as the 109 degrees of longitude." That letter was written way back in 1875. We have had plenty of time to absorb the facts. But every now and then someone notices that the Colorado/Utah stateline is not exactly on the 109th Meridian west of Greenwich. Sometimes someone in the news media latches on to this fact, and sometimes they fail to fully research the issue before announcing to their audience something along the lines of "The Four Corners Monument is off by 2.5 miles!" Claims like that are patently untrue. For one thing, the location of Four Corners (and several other state boundaries) was not defined in terms of the Greenwich Meridian -- it was never intended to be located at 109 degrees west of Greenwich. Secondly, even if a boundary monument is not located exactly where it ought to have been (which is true in just about every case, to a greater or lesser extent), once the boundary as surveyed has been accepted by the relevant jurisdictions, that becomes the legal boundary... regardless of any future claims of inaccuracy. |
But something was wrong. A 26-inch, f/16 refractor would have a focal length of almost thirty-five feet. This room was a scant twenty-five feet in diameter. As the twenty-six inch was not part of the observatory’s original equipment, it was reasonable to assume that there had been another, smaller equatorial refractor which dated from its inception. (A later trip to the Smithsonian Institution revealed a 9.5-inch lens which had once belonged to the Naval Observatory. At f/16, this lens would have a focal length of 13-feet, fitting rather nicely into the Bureau of Medicine’s modest dome.)
Further investigation revealed a likely solution to the problem. Extending south from the small dome was a narrow room, about 100 feet long. This must have been the transit room, hence the name “Old Transit House”. The Washington Meridian, which was almost selected as the Prime Meridian, must have been defined by the instruments in this room. At the southern end of the transit room is a large circular room approximately 50 feet in diameter. This would in no way cramp the style of a 35-foot telescope tube. The room is at present topped by a conical roof, and it contains a large number of file cabinets; a necessarily inefficient use of a room specifically designed for another purpose. Conversation with the workers in this room revealed that they were totally unaware of its original use. There is no indication, by historical marker or photograph, that perhaps the most unusual objects in our solar system were discovered here. Asaph Hall and Alvan Clark have been gone for many years, but to stand on this spot is to remember their achievement, and to somehow share in their great discovery. It is an experience to be recommended to everyone. |