Geology Site Account

Site name: Elm Grove Summer House, in the grounds of Elm Grove, Saffron Walden.

Grid reference: TL 5398 3828

Brief description of site:

Elm Grove is a development of flats and bungalows for older persons which were built on land which was formerly the rear garden of a large property in Audley Road, also called Elm Grove (later known as Walden Grove) which has long since been demolished. Against the eastern flint boundary wall is a small structure built as a summer house or grotto in the former garden. The summer house is remarkable as it is built almost entirely from erratic boulders brought to Essex by an ice sheet during the Ice Age. The largest boulder of all is a giant Hertfordshire puddingstone 2.6 x 1.2 x 0.8 metres (8.5 x 4 x 2.5 feet) in size, which may be the largest puddingstone boulder in Essex.

Access only available by arrangement with the Elm Grove Estate Manager.

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Introduction

The summer house is remarkable as it is built almost entirely from erratic boulders. Erratic boulders are stones that have been transported by ice and these particular examples were carried to Essex by the great Anglian Ice Sheet which covered almost the whole of Britain during the coldest period of the Ice Age, some 450,000 years ago. Boulders such as these would have been frequently found in clay pits and gravel pits which were common around Saffron Walden in Victorian times. They would also have been encountered in fields whilst ploughing.

There are at least 20 boulders here of different rock types, some of which are distinctive rocks from the north of England and Scotland. The study of erratics can provide valuable clues to the flow of ice across the country and the nature of the landscape during the Ice Age.

History

The former house known as Elm Grove was built in 1828 by Jabez Gibson (1794-1838) but he never lived there. Jabez Gibson was a well known local figure and contributor to the prosperity of the town. In 1830 he set up the town's own waterworks company and in 1832 was a co-founder of the town's Literary and Scientific Institution and the Natural History Society, which ran the town's new museum. It is likely, therefore, that he would have had an interest in what was then the very new science of geology and gathered these boulders from surrounding farmland for use in the garden, although the actual date the summer house was constructed is not known.

The boulders

At least 20 boulders have been used in its construction and at least 6 different rock types are represented. The rocks are derived from near and far, for example there are large blocks of local calcrete, a rock consisting of hard chalk fragments cemented together and two weathered boulders probably from Derbyshire: one of Carboniferous limestone (with crinoid fossils), and one of millstone grit. Of particular interest are the septarian nodules which have been cut in half to reveal the calcite-filled cracks and positioned to make the rear wall. These would have originally have been polished which would have provided a spectacular effect.

Built into the south wall is a sarsen stone about 1.2 metres (4 feet) square known as the "hangman's stone" or "sheepstealers' stone". This stone was taken by Jabez Gibson from land at nearby Littlebury that was owned by Lord Braybrooke of Audley End (Rowntree 1954). In his paper on Essex boulders, Salter (1914) states that the Littlebury sheepstealers' stone "has disappeared", clearly unaware of its new role. There is a fanciful story to account for the name of this stone (Gumbrell 1989) but it has no basis in fact. The stone is, however, of some geological interest as it has a hole passing through it that was almost certainly formed by a root of a tree that was living on the sandy ground in which the sarsen was formed, some 55 million years ago. The largest boulder of all is a giant puddingstone 2.6 by 1.2 metres (9 feet by 4 feet) in size at the base of the south wall, which may be the largest puddingstone in Essex. Part of this stone contains no pebbles and is therefore similar to a sarsen.

The only part of the structure that is not of erratic boulders is the roof, which consists of sawn slabs of imported York stone, a sandstone from Yorkshire. It is possible that this was added later.

Other information

Elm Grove was demolished in the early 1970s. The summer house is not the only structure in the garden to survive the subsequent redevelopment. In the centre of the grounds is the prominent ruin of a delightful flint 'folly' which was once used as a tiny museum.

Elm Grove is private property and permission for access must be obtained from the Estate Manager. The summer house is marked on the large scale 1919 Ordnance Survey map but inexplicably it is not marked on the most recent 1: 2,500 scale maps.

The Elm Grove Summerhouse as it is today. Photo: G.Lucy