[Geysers] Hygeia Spring area Marshall Hotel site

[Jack Ashe]

I have the following picture of the Hygeia Spring area of the very lower Lower Geyser Basin (Marshall Hotel group) that I posted on another Yellowstone forum.  Originally I thought this feature was the same as Hygeia Spring. However, as I researched the geography more, it appears (see map link below) that there is a difference between the Hygeia Spring per se and the feature with the geyserite tub.  
If so, what is the geyersite tub called (Bath Tub Spring, Bath Spring ??).  
Also, was the "tub" (the squared section at the end) manmade or natural?
 
 
http://farm4.static.flickr.com/3315/3417054706_02b3465e58.jpg?v=0
 
Map picture of Marshall Hotel layout:

http://www.nps.gov/history/mwac/marshall_hotel/images/slide_hotel/MarshallFireholeHotel/photo1.html
 
Additional general info on the Marshall Hotel history.
http://www.nps.gov/history/mwac/marshall_hotel/hotel_arch.htm


Appreciate any help or opinions

Jack