Along with daily ship positions, the log contains details of the capture of various slave ships beginning with the HENRIQUETA. Renamed BLACK JOKE, entries explain the vessel was taken into service as a tender to HMS SYBILLE in December 1827.

A table entitled "List of Slave Vessels captured by H. M. S. Sybille & Tender from May 1827 to May 1829" indicates a total of 16 ships and 3970 enslaved Africans. There is an account of the language used by some slaves, entitled “Accou Language used by Slaves from the Kingdoms of Haysa & Hio: generally taken in vessels from Whydah and Badapry” and consisting of a list of phrases and the English translation.

There are entries regarding the famous action between BLACK JOKE and the Spanish slave ship EL ALMIRANTE, wherein the latter vessel was captured. These include a list of the officers and crew on board BLACK JOKE during the action and a description of the damage the vessel sustained. Downes provides two transcriptions of letters between himself, Collier and the Admiralty in regards to the capture of EL ALMIRANTE as well as one between the Captain of EL ALMIRANTE and his Mate. An account of the action is included entitled “Memoranda. Observations and Information collected from Crew of "El Almirante" after the action" followed by a song commemorating the bravery of the BLACK JOKE’s crew entitled "Song by Thomas Eason one of the Black Joke's crew on 1 Feb 1829". A table entitled "Specimen of slave trade by Spanish brig EL ALMIRANTE at Sagos commencing Aug 25 28" lists' types of slaves' / enslaved peoples and socalled 'values in dollars'.

At the back on the log are Captain Collier's Orders to the Officers of the Sybille [written in a different hand, possibly Collier's], signed T. Collier with one dated 14 May 1827 and the second dated 12 September 1827.

One of the loose leaves appears to be part of the song by Thomas Eason and the other is a pricing list for stock.

Administrative / biographical background
Following the Abolition of the Slave Trade Act 1807, the Royal Navy was used to supress the Atlantic slave trade. British naval squadrons were set up to patrol the coast of West Africa and the Caribbean looking for illegal slavers. HMS SYBILLE, commanded by Commodore Francis Augustus Collier, and its tender HMS BLACK JOKE, commanded by Lieutenant Henry Downes, were involved the capture of various slave ships, the latter being the former slave ship HENRIQUETA captured by the Royal Navy in September 1827.