I was flicking through the online 1819's Ackermann's Repository of Fine Arts - as you do - when I came upon this fascinating snippet so I had to read more to find out what I could.
Alas, there is nothing much else I could find to add to this! It has been 'recently built and completed with entirely new and substantial materials' which as I believe this was in the June issue suggests it was completed over the spring and early summer of 1819. Fortunately the text is nice and clear! I like the idea of being able to make the depth of the bath greater or less - the latter for the more nervous bather no doubt, and for ladies who generally did not swim - which as a one-time swimming instructor I would have found very useful in the many, and often built to a compromise, baths in which I have taught. The big bath is pretty small by the standard of most swimming pools, at 24' x 8' [about 7.5m x 2.5m] of course, and the private baths at 10' x 8' little more than big puddles. However the chance of private bathing might have overcome such paucity of room to swim properly, especially perhaps for ladies who did not wish the 'incommodious and indecorous practice of public exposure in the Thames'.
What I find fascinating is the description of the Thames as 'a noble river filled with the purest and most wholesome waters in the world' which isn't the way I tend to think of the Thames, and one is tempted to raise a cynical eyebrow and wonder if this is just so much advertising hype unsullied by laws against false advertising - until one recalls the poem 'Composed upon Westminster Bridge' by William Wordsworth in 1802:
Dull would he be of soul who could pass by
A sight so touching in its majesty:
This City now doth like a garment wear
The beauty of the morning; silent , bare,
Ships, towers, domes, theatres, and temples lie
Open unto the fields, and to the sky,
All bright and glittering in the smokeless air.
Never did the sun more beautifully steep
In his first splendour, valley, rock, or hill;
Ne'er saw I, never felt a calm so deep!
The river glideth at his own sweet will:
Dear God! the very houses seem asleep;
And all that mighty heart is lying still!
O Thames! that other bards may see,
As lovely visions by thy side
As now, fair river! come to me.
Oh glide, fair stream! for ever so;
Thy quiet soul on all bestowing,
‘Till all our minds forever flow,
As thy deep waters now are flowing.