I came across this remarkable observation mentioned in Sir Robert Ball’s “Story of the Sun” (1893)
On 7th October 1892 M. Trouvelot observing from Meudon observatory records observing a black protuberance. He describes the spout of of ejected material as inky black, the temperature of its constituents, whatever their nature, having been probably much below that possessed by the ordinary luminous prominences. He also states, similar phenomena have been noticed by him on certain other days.
Bearing in mind what we know today, what do you think he saw? A shadow of a prom? Has Hinode or SDO ever seen such a thing?
I had to look up how this could have been observed, as there was no solar eclipse. Appears Young’s slits were in use, and i had the pleasure of a tour at the Late Commander H Hatfield’s observatory which employed this method in the 1970/80s. My suggestion is that it could be caused by the Doppler shift making a prom appear fainter and darker perhaps.