Free Chatham Dockyard by Philip MacDougall Page A

Admiralty concurred, agreeing that one dry dock should be built immediately with its construction placed under the overall supervision of Rennie. This new dock was to be of a much greater depth than the four existing docks and would be built of granite rather than timber. To be sited immediately to the north of the Old Single Dock, it would eventually be known as the No.3 Dock. At this point, some reference needs to be made to the overall numbering of docks, as the names originally used to distinguish each of the docks had ceased to have any relevance, leading to each being consecutively numbered. Thus, the original Double Dock (renamed the South Dock during the early eighteenth century) was now the No.1 Dock and the Old Single Dock was the No.2 Dock. In turn, the First and Second New Docks, situated further to the north and subsequently known as Nos 3 and 4 Docks would eventually be renumbered as docks 4 and 5, to make way for the new stone dock that was now to be built between the old Nos 2 and 3 Docks. For a time, this also meant that Chatham had five dry docks not four. This was only a temporary situation as, shortly after, the Old No.4 Dock (new No.5) was converted into a building slip. In turn, this also resulted in a consecutive renumbering of the slips, with the former dock having become No.3 Slip. From now on, therefore, all docks and slips will be referred to by the numbers that they had acquired following both the completion of Rennie’s new stone dock and the conversion of the No.5 Dock into a building slip.
    Rennie provided a description of his proposed design for the new stone dock in a letter sent to the Navy Board in August 1815:

A view of the interior of the ropery, looking along the length of the laying floor.
The size of the dock is conformable to dimensions furnished me by the Surveyor of the Navy. The floor is proposed to be 4 feet under the level of low water of an ordinary spring tide, which according to Mr Parkin’s information rises 18½ feet, thus giving 22½ feet of depth at the high water of a spring tide, which I am informed will be sufficient not only to float a first rate but also admit of the proper sized blocks under her keel. At this time therefore there will be 4 feet of water to pump out of the dock at low water Spring Tides, and about 9 feet at neap tides, and for this purpose a steam engine will be required.
    To this he added a series of estimates as regards its overall cost:
First, supposing the whole of the altars, floor and entrance to be made of Aberdeen granite. In which case the probable expense of the dock, admitting the whole to be set on piles, which from Mr Parkin’s borings I fear will be necessary, amount to £143,000. The steam engine, engine house, well and drain, amounts to £14,700; and working her for two years while these works are in hand £2,000. 2
    Work on constructing the new dock was undertaken by John Usborne and Benson, a privately owned construction company, with John Rennie given access to the work at all times. The contract was signed on 16 February 1816 with payments made by the Navy Board at the rate of £1,000 for completion of each of a series of stipulated units. A separate pump house, this to accommodate a 50hp Boulton & Watt steam engine to be used in draining the dock, was also to be constructed. Situated immediately behind the new dock and on land formerly used for the storage of timber, this building was to be constructed by the dockyard’s own workforce. Originally it was hoped that the new dock would be available for use during the early part of 1819, or even earlier, but a number of delays, primarily due to the contractors under-ordering materials and scrimping on the number of artisans employed, meant that it was not to be finally completed until 1821 and resulting in a total cost that amounted to £182,286.
    Rennie’s dry dock must be considered an important and significant feature of the yard, being the first to be built in the yard of a