Large crinoline skirt with two bodices. A long-sleeved bodice with a demure neckline and long flared sleeves trimmed with black bows, and a low-cut evening bodice with a Chantilly lace bertha around the neckline,
tiny puffed sleeves, and black jet braid. The skirt would go over quite a large hoop. This was probably made around 1861 as social mourning, following the death of Prince Albert. Because there is an evening bodice, it wouldn't have been family mourning as if a relative had died, you wouldn't be going to balls or dances. It was probably worn by quite a young lady, or a recently married woman, as the bodices are quite simple.
to see a photo of a lady from c. 1861 wearing a similar dress in the same fabric.
(Dress from the Milford-Cottam collection, photo L. Hidic)