Definition of "atramentous"

The second way whereby bodies become blacke, is an atramentous condition or mixture, that is a vitriolate or copperose quality conjoyning with a terrestrious and astringent humidity […]

1650, Thomas Browne, Pseudodoxia Epidemica: […], 2nd edition, London: […] A[braham] Miller, for Edw[ard] Dod and Nath[aniel] Ekins, […]

Perdido Street Station was the centre of the city, even more than Parliament, the atramentous keep now empty of functionaries […]

2004, China Miéville, Iron Council, Trade paperback, published 2005, page 464