Py..

Natural cement cost less than portland cement in the 1890's, so they tended to use portland where they needed the higher, faster strengths.

Ken is right about the lighthouses being controlled by Totten - Corps of Engineers took over the lighthouses due to corruption and poor illumination resulting in shipwrecks. Totten personally designed at least one that I know of, and we have been finding natural cement in mortar analyses and Historic Structures Reports for lighthouses from the 1830's on along the east coast.

The 1835 Pemaquid Point lighthouse in Maine was recently restored using natural cement mortar and a natural cement whitewash:
http://www.wcsh6.com/news/article.aspx?storyid=71268  (There's a video too). I think our mineral coating looks pretty good too.

Mike E

..how was natural cement used in the forts at this time (1890) was it used to encapsulate and protect the lime portland as  the natural  was too expensive for the bulk of the pour ....or was its use case by case as i suspect
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> ..lastly is there any evidence that the light house engineers were the one and the same with the army corps engineers ...did they not share the same specs ?