Thames Head or Seven Springs?

1910: Thames Valley Villages by Charles G Harper

The Critical Review, Or, Annals of Literature By Tobias George Smollett, 1801 -

Like the source of the Nile, the position of the original fountain of the Thames has been variously assigned, and its birth place has been almost as much contested as that of Homer, by divers contributing springs on the borders of Glocestershire and Wiltshire, through which its several early branches hasten to form their union previous to their reaching Oxfordshire.
Cricklade in Wiltshire is the central town of this district ;
and some attribute, the honour of forming the head of the Thames to a clear fountain in its vicinage, which has long borne that title, and been considered almost as a consecrated spot by the veneration of the surrounding villages ;
while others prefer a stream issuing from the vicinage of Kemble, marked by its neat spire;
others again take the rivulets which advance from Swindon and Highworth in Wiltshire (one of which is called the Rey) ;
and many argue for the Churn of Glocestershire, which rises in the hilly tract of the Cotteswold, encircling the vale of Cheltenham, and flows to the south-east, by Cirencester, and through the extensive woods of lord Bathurst, to Cricklade.
The dispute is not of consequence, as none of these fountains, in their origin, differ materially from a common rivulet, and each county may innocently enjoy the fancied distinction, while the subjects of their contention unite near Letchlade, and creep in obscurity through the plain of Oxfordshire, attended for some distance by the parallel canal, which has been lately made, with immense expense, to join the Severn with the Thames, and so to form what should seem to be the most important inland navigation of Great Britain, by transporting the influx of foreign as well as internal wealth to and from the capital.
This canal ... perforates the long subterraneous tunnel of Saltperton in Glocestershire; but even when it advances to the river, does not form its junction immediately, but pursues a similar course to Letchlade, on the west of which place the Coin descends from the pleasant villages of Bibury and Barnsley; and on the east, the Lech, from North Lech, adds its tributary forces ; after which the combined streams bear together the classic name of the Isis. Here the navigation of this river probably commences ; but it is understood to be long very imperfect, from its winding course and its prevailing shallows ...

What is the source of a river?  There is no obvious one right answer. In the end we are not dealing with a scientific issue but in the broadest sense a spiritual issue.
1869: The Saturday Review, part of a Report of a Lecture by Professor Huxley -

... The source is said to be at Thames Head, but the sources are countless, and are all round the basin of the Thames, in the springs that rise at the edge of the hills that enclose it.
The springs led him to consider the rain, snow, and hail – clear enough for a child to understand, and interesting enough for a man to listen to. At last, he passed into almost eloquence as he showed how the sea supplies the air with the vapour of water, how the vapour of water passes into rain, how the rain supplies the springs, and the springs the river, and how the river in its turn supplies the sea.
"The source of the Thames comes from nowhere; it turns round in a circle."

The editor was unable to resist moralising on this:

He might have remembered, however, that a thousand years before the Thames was heard of, this truth had been known, and that the Preacher had said:
"All the rivers run into the sea; yet the sea is not full;
onto the place from whence the rivers come, thither they return again."

The Thames has two sources for which claims are made:

Stone at Thames Head
The Stone at Thames Head
Old Father Thames was here for 14 years.

Stone at Seven Springs
The Stone at Seven Springs.
"Here, O Father Thames, is your sevenfold Spring".

Thames Head is the currently dry spring at the head of the river, marked on maps as The Thames or Isis, a mile or so north west of Kemble.  It is at about 300 feet above sea level.  Two fields further down is Lyd Well, an active spring, from which the river flows.  The river wanders rather tentatively through flat meadows. And eventually into the Cotswold Water Park with its 150 acres of water.
Seven Springs is a much more impressive place.  It is at about 700 feet above sea level.  It is at the head of a real valley with steep hills.  The River Churn really does flow from the Springs and immediately forms a small lake.  It leaps down the valley and then joins the Hilcot Brook.  The lovely Rendcomb valley begins to flatten until it approaches Cirencester.  It eventually also comes to the Cotswold Water Park and joins the other stream a few yards downstream of Cricklade Bridge.  Seven Springs feels much more like the source that Father Thames would be proud to own.

1692: Baskervile is on the side of Seven Springs -

Criclad Bridge -
... The Bridges and Casway to go into Glocester shire from Cricklade are 580 paces or yards long, to the farther side of ye bridge over that stream which comes from Cyrencester [ i.e. the River Churn].
The other stream runs by Ashton Canes comes in by Cricklad Town.
The 2nd Bridges viz That Bridge over Ashton Canes stream,
and that bridge over Tems or Cyrencester stream and ye casway between,
have 12 arches for water to pass.

[ So Baskervile calls the “Cyrencester Stream” “Tems”,
and the other source “the Ashton Canes Stream”.

1845: The Penny magazine of the Society for the Diffusion of Useful Knowledge

Spenser's account of the origin of "the noble Thames" was only a poetic version of the opinion generally adopted in his day by sober geographers and antiquarians :—

"Him before there went, as best became,
His ancient parents, namely the ancient Thame;
But much more aged was his wife than he.
The Ouse, whom men do Isis rightly name."

That the upper part of the river was properly called the Isis, and that the name Thames arose from its junction with the Thame at Dorchester, a few miles below Oxford, seemed to be admitted without question, not only in Spenser's time, but long afterwards, and is still commonly asserted..
It is however a mistake. Isis is only a scholarly name given to it, probably from the termination of its Latin form, Tamisis. In none of the ancient documents in which it is mentioned does the name Isis occur. The credit of having been the first to notice this is usually given to Camden, but that excellent old antiquary appears not to have suspected the truth of the common notion. The Latin poem called the 'Marriage of Thame and Isis', in which the union of the streams is celebrated with all the fulness a marriage producing such issue deserved, is even attributed to him by his biographer..
It was Bishop Gibson, in his 'Additions to Camden,' who pointed out the error, and cited the various authorities in proof that it was an error, and the mistake of attributing it to Camden no doubt arose from the manner in which the additions are mixed up with the original text. The following are his words (Gibson's Camden's ' Britannia,' i. 194, ed. 1772) :—.
"Upon this first mention of the river Thames, it will not be improper to observe, that, though the current opinion is that it had that name from the conjunction of the Thame and the Isis, it plainly appears that the river was always called Thames, or Tems, before it came near the Thame.
For instance, in an ancient charter granted to Abbot Aldhelm, there is particular mention made of certain lands upon the east part of the river, 'cujus vocabulum Temis, juxta vadum qui appcllatur Summerford' (the name of which is Thames, near the ford called Somerford), and this ford is in Wiltshire. The same thing appears from several other charters granted to the abbot of Malmsbury, as well as that of Evesham; and from old deeds relating to Cricklade. .
And, perhaps, it may with safety be affirmed, that in any charter of authentic history it does not ever occur under the name of Isis, which, indeed, is not so much as heard of, but among scholars; the common people all along from the head of it to Oxford calling it by no other name but that of Thames.
So also the Saxon Temese (from whence our Tems immediately comes) is a plain evidence that that people never dreamt of any such conjunction. But further, all our historians who mention the incursions of Ætholwold into Wiltshire, A.D. 905: or of Canute, A.D. 1016; tell us that they passed over the Thames at Cricklade.
This may suffice as to the name of the river: but we are not yet in a condition to speak of its source, for that has been also a moot point, and is hardly now a decided one. Most rivers are at their head separated into a number of small streamlets, of which some one has generally the pre-eminence conceded to it, from its superior size, or its being the remotest from the mouth of the river. As this is the principal stream, its spring is called the source. .
Two streams contend for the honour of the parentage of the Thames. Both rise from the southern slopes of the Cotswold Hills, but some sixteen miles apart. The source of one is known as Thames-head, of the other as Seven Springs..
The one which flows from Thames-head would seem at first sight to have the fairest claim. Its source has ever been called Thames-head by the inhabitants of the neighbourhood; and the stream itself has always been called the Thames, long before it meets the other branch, which, on the other hand, has always been known by another name. But then it must yield to its rival both as regards the distance of its source from the main trunk and its size — and whatever may have been the received opinion, the Churn is now considered by geographers as the true head of the Thames. .
We will look briefly at each, and trace them from their springs till they meet and form one river.

See the Thames Head and Seven Springs pages

1937: In the House of Commons, Mr Perkins was the Member for the Stroud constituency which included Seven Springs.
The Minister for Agriculture was the Member for Cirencester, the Constituency which included Thames Head -

Mr Perkins asked the Minister of Agriculture whether he is aware that, on the most recent edition of the Ordnance Survey Maps, the source of the River Thames is shown as Thames Head, in the parish of Coates: and in view of the fact that the source known as Seven Springs, in the parish of Coberley, is farther from the estuary, he will undertake that in the next edition of the Ordnance Survey Maps the correct source will be marked.
The Minister for Agriculture, Mr W S Morrison: I understand that it is not an invariable rule in geographical practice to regard as the source of a large river the source of the tributary most distant from its estuary. I am advised that the source of the Thames or Isis is the spring known as 'Thames Head' and that the leading authorities agree that the name of the stream which rises at Seven Springs is the Churn. In these circumstances it does not appear that the alternative suggested would be justified.
Mr Perkins: Is the right honorable Gentleman aware that the source known as ‘Thames Head’ periodically dries up -
An Honorable Member: Why don't you? Laughter.
- as in 1935, and is he also aware that the source known as Seven Springs is twice as high above sea-level as the source known as Thames head, as well as being farther from the estuary?
Mr Morrison: I am aware of these considerations, but they do not alter my view, as confirmed, that the River Thames rises in my constituency and not in that of my honorable friend ...
I think there is no doubt that the Thames rises in the parish of Coates

[ In 1937 the House of Commons had more worrying matters to deal with and this somewhat ponderous exchange is all we have from our legislators on the subject. ]

1949: Paul Gedge, Thames Journey (at Seven Springs) -

The wall bears a Latin hexameter, cut in a slab;
In other words, “Here'’s the source”.
And who can reasonably disagree?  Account Thames Head the sentimental source if you like, but to trace the True Source of the Thames to a spot where there is seldom any Thames at all, or to hail a stream issuing from a pump as London’'s river, while this clear, natural spring pours out its waters all the year round, at a considerably greater distance from the sea, is, to me, something of a reductio ad absurdum.