Shipboard desalination, 1684, UK

Jim Birkett writes of a possible shipboard desalination trial by the 17th-century English navy:

Facsimile of Pepys’s letter about a shipboard desal trial, 1684 – Jim Birkett
Facsimile of Pepys’s letter about a shipboard desal trial, 1684 – Jim Birkett

'We do know that in 1684 Samuel Pepys (the diarist, then Secretary to the Admiralty Commission) wrote to a Captain Gifford of His Majesty’s Ship Mermaid, asking Gifford to participate in a desalting experiment with a device to be supplied by the Court.

'The letter reads as follows:

Whereas a Proposal has been made to Us of an Engine to be fixed in one of Our Ships for the making an Experiment of producing fresh water (at Sea) out of Salt, Our will and pleasure is, That, upon application to you by ye Persons concerned in ye said Engine, you doe receive ye same on board, and arrange it (at their Charge) to be fixed in some convenient place in Our Ship, in Order to your making ye said Experiment in yor present Voyage, and Reporting to Us yor Observations upon it, for Our Satisfaction, upon your Returne: Provided that you be first satisfyed that ye same may be put up and made use of, without any sort of danger to Our Ship by Fire or otherwise. For wch this shall bee your Warrant. Given at Our Court at Windsor this third day of August 1684.

'The letter is signed "S. Pepys" and the large hand-written "Charles R" at the top of the page indicates that the letter is official business of the King. We do not know whether or not Captain Gifford cooperated or, if he did, what the outcome was of the experiment. One may easily speculate that the still was of the Fitzgerald design (Fitzgerald had filed a patent on seawater distillation the previous year and was engaged in a dispute with another patentee, Walcot) and that the experiment was to do some field testing.'