Archaeologia Volume 13 Section IX is in Archaeologia Volume 13.
Account of the Fall of some of the Stones of Stonehenge, in a Letter from William George Maton, M.B. F.A.S. to Aylmer Bourke Lambert, Esq. F.R.S. and F.A.S. Read June 29, 1797.
Having lately had more leisure to make remarks on the alteration produced in the aspect of Stonehenge, by the fall of some of the stones in January last, than when I first visited the spot for this purpose, I am anxious to lay before the Antiquarian Society a more full and correct account of it than that which you did me the honour to transmit to them before.
On the third of the month already mentioned some people employed at the plough, full half a mile distant from Stonehenge suddenly felt a considerable concussion, or jarring, of the ground, occasioned, as they afterwards perceived, by the fall of two of the large stones and their impost. That the concussion should have been so sensible will not appear incredible when I state the weight of these stones; but it may be proper to mention, first, what part of the struture they composed, and what were their respective dimensions.
Of those five sets, or compages, of stones each consisting of two uprights and an impost which Dr. Stukely expressively termed trilithons, three had hitherto remained in their original position and entire, two being on the left hand side as you advance from the entrance towards the altar-stone, and one on the right. The last mentioned trilithon [a] is now levelled with the ground. It fell outwards, nearly in a western direction, the impost in its fall linking against one of the stones of the outer circle, which, however, has not been thereby driven very considerably out of its perpendicularity. The lower ends of the two uprights, or supporters, being now exposed to view, we are enabled to ascertain the form into which they were hewn. They are not right-angled, but bevilled off in such a manner that the stone which stood nearest to the upper part of the adytum is 22 feet in length on one side, and not quite 20 on the other; the difference between the corresponding sides of the fellow-supporter is still greater, one being as much as 23, and the other scarcely 19 feet, in length. The breadth of each is (at a medium) 7 feet 9 inches, and the thickness 3 feet. The impost, which is a perfect parallelopipedon, measures 16 feet in length, 4 feet 6 inches in breadth, and 2 feet 6 inches in thickness.
Note a. Marked [Black Letter Lowercase H] in Smith's Choir-G-aur. This tnlithon might, with great propriety, he caiied the weftern, as no one of the others food more nearly wef of the center of the ltrudlure.
Now, a cubic inch of the substance [b] of which the above ftones are composed, weighing, according to my experiments, 1 ounce 6 pennyweights, the ponderosity of the entire trilithon will be found to be nearly 70 tons. The impost alone is considerably more than 11 tons in weight. This stone, which was projected about 2 feet beyond the supporters, made an impression in the ground to the depth of seven inches, or more; it was arrested in its tendency to roll by the stone it struck whilst falling. The supporters, of course, have not sunk so deep; indeed, one of them fell on a stone belonging to the second circle, which I at first supposed to have been thrown down by it, but which, from recurring to plans of the prior state of the structure, I find to have long been prostrate.
Note b. This is a siliceous grit, of rather a loose texture, and of a dull whitish colour, with veins of brown, which seem to be occasioned by the oxydation of the iron contained in it. All the stones of the great oval, and most of those of the outer circle, consist of this species of rock.
Though I could not contemplate without emotions of peculiar awe and regret such an assault of time and the elements on this venerable structure, I must own these emotions were in fome measure counterbalanced by the satisfaction of being now enabled to discover the original depth of these stupendous stones in the ground. It appears that the longer of the supporters was not more than 3 feet 6 inches deep (measuring down the middle), nor the other but little more than 3 feet. In the cavities left in the ground there were a few fragments of stone of the same nature as that forming the substance of the trilithon, and some masses of chalk. These materials seem to have been placed here with a view to secure the perpen dicular position of the supporters.
The immediate cause of this memorable change in the state of Stonehenge must have been the sudden and rapid thaw that began the day before the stones fell succeeding a very deep snow. In all probability the trilithon was originally perfectly upright, but it had acquired some degree of inclination long before the time of its fall. This inclination was remarked by Dr. Stukely, though it was not so confiderable, I think, as is represented in his north view of Stonehenge. One of the supporters had lost much of its original bulk in consequence of corrosion by the weather, near its foundation; this circumstance also rendered it less secure. As both had so inconsiderable a depth in the ground, a sudden, though slight, diminution of the pressure of the latter against the inclining side must appear to have been fully sufficient, on account of the shock which the impost would suffer, to occasion the downfall of the whole.
We do not find the precise time of any alteration prior to this upon record; it is therefore probable that none may have happened for several centuries, and the late accident being the only circumstance ascertained with exactness may be considered as a remarkable æra in the history of this noble monument of ancient art.
I am, with every sentiment of respect,
Your sincere and obedient servant,
William George Maton.
London, May 30, 1797.