I had the opportunity to tour these caverns a few years back.  The Park Service
was running some interesting environmental monitoring programs on both Lincolnd
and Jefferson.  I was running one on a very tiny building in Western Pennsylvania
with similar issues if not on the same scale...in fact if there is such a scale,
this is the opposite end.  Anyway, I'm sure the guys in the funny hats would be
able to give you much more uptodate information on the cause and character of
these caves than 1968.

Wow!  Thank you Tom Potter!  (He told me that my roll o dex was the most
important thing to take from one position from the next and now it pays off!)
Our tour guide was Audrey T. Tepper, Historic Preservation Architect, NPS.  She
was about to take a leave, but she was running the project and certainly knew
those "caverns" well enough to write an update to your 1968 article!

It was very cool.  But long after I've forgotton the caverns I will look at my
right hand and remembering it being close enough to touch the inside top of the
dome at Jeffeson.  Is this a cool profession/obsession or what?

-jc

Ken Follett wrote:

> STALACTITES UNDER THE LINCOLN MEMORIAL, Science & Mechanics, August 1968.
>
> (This is the same issue that carried Part 2 of the series, _Ithaca's
> Terrifying Flying Saucer Epidemic_, featuring Jimmie Orr in the swampy area
> behind the house of Mrs. Anna "X", that is, before he became a local cop. I'm
> looking for a July 68 copy of S & M.)
>
> Few, if any, of the hundreds of thousands of annual visitors to the Lincoln
> Memorial realize that just a few feet below them, within the underground
> concrete foundation of the Memorial, is a scene reminiscent of the scenic
> caverns of the world.
>
> Scientists of the Department of the Interior's National Park Service, and
> Geological Survey report that stalactites -? deposits of calcium carbonate
> normally found in caves -? are growing down from the foundation ceiling.
> Also, short, stubby stalagmites rise a few inches from the foundation floor.
>
> According to William Newman and Charles Withington, geologists of the U. S.
> Geological Survey, and Maurice Sullivan, and Ellsworth Swift, naturalists of
> the National Park Service, "the icicle?white stalactites range in length from
> a few inches to as much as five feet or more. Their diameters are generally
> less than an inch; most are a half inch or less. A few of the stalactites
> have grown sufficiently long to connect with their corresponding stalagmites,
> forming a continuous mineral link between ceiling and floor."
>
> The best display of stalactites is in the farthest reach of the foundation,
> particularly in the general area beneath the surface steps that rise from the
> roadway. "The foundation area, however, in which the phenomenon is observed,
> is not open to the public," the, Park Service said.
>
> "Although the growth rate no doubt varies from year to year, and from place
> to place beneath the Memorial (completed in 1923), some stalactites appear to
> be growing at an average rate of more than an inch a year," Newman and
> Sullivan said.
> Explaining the processes that form the "dripstone" features, geologist Newman
> said that "the stalactites and stalagmites beneath the Lincoln Memorial form
> in a manner similar to those found in natural caverns in many parts of the
> world. Water, carrying calcium carbonate in solution, percolates through
> cracks in the concrete slab and support?works upon which the Memorial rests.
>
> "As the water drips along the cracks and evaporates," Newman continued,
> "calcium carbonate is deposited around the margin of the drop in the form of
> a zing. Successive drops make additional minute deposits which grow downward
> to form a hollow tube. If a stalactite is sliced into disks, the cross
> sections show concentric growth rings that resemble the layered structure of
> an onion."
>
> The source of the calcium carbonate, according to ?the Survey and Park
> Service spokesmen, is difficult to pin down, but there are several
> possibilities: the marble flooring and the trim of the Memorial itself, or
> the mortar used in its construction; the concrete forming the massive
> underground foundation; or the cement matrix of the cobbled steps and walkway.
>
> Continuing studies by naturalist Ellsworth Swift, of the National Park
> Service, are being made to determine accurately the growth rate of the
> curious stone "Icicles."
>
> ===========
> ][<en