This painting was made around 1789 or perhaps early 1790 and there is a wealth of detail in it.
The viewpoint appears to be opposite what is now the Sun Pier area. The large three-decked ship on the right hand side of the picture is the 100 gun first rate ship HMS Royal George, launched in 1788 as a replacement for the slightly smaller ship of the same name which had foundered at her mooring at Portsmouth in 1782. From the incomplete state of her masts and the fact that all the gun ports are open but no guns are run out, the ship is being fitted out, which fits the above dates. HMS Royal George was built on the No.1 slipway, which can be seen empty on the right hand side of the painting. She was the 1st first rate ship ever to be built on a slipway rather than in a dry-dock and the slipway is probably in the process of, or is about to be prepared for the start of the next project - the construction of HMS Ville de Paris.
The next vessel, shown on the No.2 slipway in frames, would be the 16 gun ship-sloop HMS Rattlesnake which would be launched in 1791.
The next vessel, a large three-decker in the No.1 dry dock would be the 100 gun first rate ship HMS Queen Charlotte. That ship is shown here in the final stages of her construction and would be floated out in 1790.
The next dry dock, No.2, contains a two-decked ship of the line whose identity is uncertain. The best candidate I can find is the 64 gun third rate ship of the line HMS Scipio. That ship is shown as having been serving as Guard-Ship at Chatham between November 1786 and November 1789, when she paid off. The ship was recommissioned under Captain Thomas Pasley in March 1790 and was fitted for sea, completing that process in May. This was presumably as part of the mobilisation of the fleet for either the Spanish or Russian Armaments Crises of that year.
The process of fitting a ship for sea after a period in harbour service would have involved dry-docking the ship for a thorough inspection of the hull and re-coppering if needed. It's therefore very likely that HMS Scipio would have been in one of Chatham's dry-docks during the time that Nicholas Pocock made this painting.
HMS Scipio spent almost her entire 16-year career as a Guard-Ship, either at Sheerness or Chatham. Built under contract by William Barnard at Deptford and launched in October 1782, the ship went to sea for the first time in August 1795 when she saw service in the Caribbean. The ship returned to the UK in September 1797 and was broken up at Chatham in October 1798. Her final commander was Captain Charles Sydney Davers, who, after paying off HMS Scipio at Chatham, was appointed to command the frigate HMS Active, then under construction in the Royal Dockyard. See here:
No 3 dry dock appears to be empty, while No.4 dry dock contains another two-decker, which from the scaffolding around her, appears to be in the final stages of being built. Given the dates, that ship could only be HMS Leviathan, a third rate ship of the line of 74 guns.
Turning now to the vessels in the river:
In the left foreground, we have what appears to be a pair of Dutch sloops in the process of either loading or unloading. In the centre foregound, just offshore is what appears to be a mooring vessel, judging by the boom over the bow and the cable going vertically into the water. Perhaps this is one of the mooring vessels built for the Dockyard by Edward Muddle at Gillingham.
Centre-right, just ahead off the port side of HMS Royal George is what appears to be a Yacht. This small, single masted vessel, which from her ornate stern carvings, the fact that she's flying a Union Jack from the end of her bowsprit and a commissioning pennant from her mast, means that she is probably HM Yacht Chatham. She was assigned to the Resident Commissioner at the Royal Dockyard and was used to carry him to and from meetings at the Navy Board offices in London and on any other official business.
Left of centre is what appears to be a frigate waiting to have her masts fitted, either having recently come out of the Dockyard or being fitted for sea after a period in the Chatham Ordinary. Moored alongside her is a two-decked ship of the line. Behind those two is another vessel, in the process of having masts fitted as evidenced by the sheer hulk moored alongside.
Further downstream there is another two-decked ship of the line and what appears to be a frigate behind her.
Also visible in this painting are the Commissioners House, the Clocktower Building and the Sail and Colour Loft, all of which are still standing.
