One-inch Map Research Articles

Survey of India : Annual Report

THE Survey of India has issued a Civil Activities Report covering the period April 1, 1945–March 31, 1946, which replaces the detailed General and Geoderic Reports which have been in abeyance since 1939 but are to be introduced for the year 1946–47. Much of the work of the Survey during the year was directed towards the furtherance of a number of long-term projects, such as the Kosi, Mahanadi and Tista irrigation schemes. For these schemes somewhat rigid priority assessments had to be made owing to the shortage of men and instruments, and new and cheaper survey expedients were adopted to provide preliminary information. Even so, the routine topographical programme received scant attention. With the widespread resumption of civil surveys, the concentration of resources in Dehra Dun has been reversed, and the Eastern Circle controlling work in Assam, Bengal, Bihar and Orissa has been re-established in Shillong. The Southern Circle has been re-created ; but map publication is still largely concentrated in Dehra Dun, where also the projects officer is located. No new or revision topographical surveys or forest surveys were carried out during the year ; but two settlement surveys were undertaken in the hilly districts of Kulu and Almora. Considerable progress has been made in replenishing stocks of quarter-inch maps corrected up to date ; but for one-inch maps the present policy is to reprint the maps uncorrected pending the opportunity for surveying the necessary corrections. The series comprises 4,100 sheets, and in issuing corrected editions a start will be made with the most developed regions.

I.— The Teschenite-Picrite Sill of Saltcoats, Ayrshire

1. Introduction. The Carboniferous rocks at Saltcoats, Ayrshire, are intruded in the vicinity of the harbour by a complex of sills and dykes. Of the sills, the two largest are composite intrusions composed of teschenite and picrite, together with allied rock types. They form two promontories, on one of which is built the quay, and on the other the bathing station and pavilion. The sill which underlies the latter buildings has hitherto lacked a detailed examination, and as the exposures showed clearly the composite nature of the intrusion it was thought that an investigation would be merited. To distinguish it from the smaller sill which underlies the quay and terminates seaward in the Inner Nebbock, it is herein referred to as the Saltcoats Main Sill. The original mapping of the area by the Survey was done by the brothers Geikie, the one-inch map being issued in 1870 and the memoir in the following year. At a later date the relationship of the sill to the underlying coal was described by one of these authors (Geikie, A., 1897, fig. 255). The area was revised by the Survey after 1911, and the results published on the one-inch and six-inch maps. A brief description of the sill is given in the Memoir to Sheet 22 (Anderson & MacGregor, 1930, pp. 267-268). These workers regarded it as the faulted continuation of the Castle Craigs sill at Ardrossan, a mile to the west. This intrusion had already been described by Falconer (1907, pp. 605-607). The This 250-word extract was created in the absence of an abstract

The New Edition of the One-Inch Map: Review

The New Edition of the One-Inch Map: Review

XXVI.— An Occurrence of Late-Glacial Clays at Ormaig, Loch Craignish, Argyllshire

In the summer of 1941, while engaged in archaeological research in the Craignish district of Western Argyllshire, the writer came upon an exposure of shelly clays in the left bank of the Eas Mor, a small stream entering Loch Craignish at Ormaig farm, and about 50 ft. from its mouth (Ordnance and Geological Survey One-Inch Map, Sheet 36). As this occurrence has not previously been noted it seems desirable to place a short account of it on record. The locality is easily found, situated as it is close to the boundary wall between Ormaig and Old Poltalloch estates, about 3 miles north-west of Kilmartin village. The writer’s attention was first drawn to the occurrence by the discovery of large masses of shelly clay in the bed of the stream, and further investigation showed that the source of these was an 11-ft. vertical face in the left bank. The succession at this point was:— The shelly clay, estimated to lie 5 ft. to 10 ft. above high-water mark, yielded numerous entire shells, clusters of complete Balani, and some Balani adhering to a stone. Specimens collected during the summers of 1941 and 1942 have been identified as follows:— The succession of beds at Ormaig is closely This 250-word extract was created in the absence of an abstract

The Cambrian Rocks of Arvon

Some eight or nine tracts are now recognized. At Bangor there are two, and an isolated one at Carnarvon;the rest are in the Tregarth country. On the older one-inch maps, all of this was coloured as Cambrian, but during the “25-inch” survey, the greater part of it had to be transferred to Arvonian, reducing the Cambrian to a group of outliers.

The Middle Jurassic rocks of Yorkshire : A petrological and palaeogeographical study

I. I troduction I n Yorkshire the rocks of Middle Jurassic age consist largely of non-marine sandstones and shales usually spoken of as the Estuarine beds. Middle Jurassic times commenced and concluded with marine conditions and there were three marine invasions during the period. In these invasions the sea apparently did not extend over the whole area; hence, although the marine beds divide the Estuarine beds into as many as four divisions, in some places two or three of these divisions merge into one (Table I). In the present paper the Cornbrash is not dealt with, and the Dogger is referred to only in so far as is necessary for an understanding of the sediments above it. Although the term Middle Jurassic is usually understood to include these beds, I have ventured, for want of a better term, to use it in this paper so as to imply the exclusion of them. Where precision of statement is called for, the contractions shown in Table I will be used. The Estuarine beds with their marine divisions attain a maximum thickness of nearly 700 feet in the neighbourhood of Ravenscar. Their outcrop on the " solid " map (Geological Survey one-inch map, sheets 33, 34, 35, 42, 43, 44, 52, 53, 54, 63, 72) covers about 380 square miles; but as the outcrop is very irregular in shape, the area over which reasonably safe conclusions as to the conditions of deposition can be drawn is not less than 1500 square miles. Stratigraphy and palaeogeographical

XIII.— The Triassic Rocks of the Annan Basin, Dumfriesshire

1. Introduction. The Annan Basin of Triassic rocks has an area of approximately fifty-five square miles, lying in Sheets 6, 10 and 11 of the One-inch Map of Scotland. It stretches from the River Annan eastwards to the Esk; on the south it is bounded by the Solway Firth, and its northern margin is an irregular line running roughly eastwards from Springkell to Canonbie (Fig. 1). The rocks of the basin are continuous with those of Cumberland on the east, but the relationship to the south below the waters of the Solway is uncertain. The area here referred to as the Annan Basin is the Scottish portion of the wide Solway Basin. The drainage of the area goes to the Solway Firth by the Rivers Annan, Sark and Esk and the Kirtle Water. The country rarely reaches 400 ft. above sea-level and, except for a few peat mosses, is given over to agriculture. There is an almost continuous cover of glacial deposits, and consequently rock exposures are practically confined to the rivers and the numerous disused quarries. Building-stone of excellent quality was formerly produced at many quarries, but only one, at Corsehill near Annan, is now working. Previous Literature. A list of publications referred to in the following paragraphs is given on page 179. The last paper dealing in detail with the rocks of the Annan Basin was that by Horne and Gregory, published in 1916 in the Transactions of the Geological Society of Glasgow; this paper gives a statement This 250-word extract was created in the absence of an abstract The writer wishes to record his indebtedness to Professor A. E. Trueman for helpful discussions of critical sections in the field and to Mr. V. A. Eyles for information about a boring in the Lower Carboniferous near Corsehill Quarry.

The geology of Helvellyn and the southern part of Thirlmere

Since the official examination by the Geological Survey in the seventies of the nineteenth century, more recent work on various portions of the Lake District, carried out by Mr. E. E. Walker, Mr. J. F. N. Green, the late Professor Marr, Dr. G. H. Mitchell, and the present author, has shown that acid rocks are widespread throughout the area and, as foreseen by Sir Archibald Geikie, that their outcrops furnish important facts which any interpretation of the structure of the district, to be convincing, must explain. The original object of the present communication was to describe the development of this type of rock in the neighbourhood of Helvellyn, an area which, since the time of Clifton Ward and J. J. H. Teall, has received only passing and incidental mention. As the work progressed, however, it was found necessary to extend the investigation and to include the mapping and description of the whole of the Borrowdale Volcanic Series as found in this particular area. J. C. Ward, who described the Helvellyn range very thoroughly, fully recognized that an unusual type of rock was present in this locality. He discussed it in detail in his memoir (1876, p. 24), but, led astray by his views as to its metamorphic origin, he failed to map it in detail. He made no attempt to separate these flows of acid lava, but included them with other rocks on the one-inch map, indicating them by a symbol representing “mostly altered ash”. This vital omission excludes from

The composite dike at Brockhill, Worcestershire (With Plate XXIII.)

At Brockhill in Worcestershire, some 11 miles west of Droitwieh, in the valley of the river Teme, a small dike of igneous rock is intruded into the red marls and sandstones of the Downtonian Series.The dike was figured and described by Phillips in 1848. On the Old Series one-inch Sheet 55 N.E. it was indicated as having a very limited outcrop on the eastern side of the river Teme; but a report of an excursion to Brockhill in 1874 records the presence of igneous rock on the opposite bank. The intrusion was examined during the resurvey on the six-inch scale of the New Series one-inch map, Sheet 182 (Droitwich), and is of interest both on account of its petrographic character and its remoteness from other igneous rocks. It has recently been traced by magnetic methods for a distance of over three-quarters of a mile.

V.— The Outlier of Carboniferous Rocks at Bridge of Awe, Argyllshire

During an inspection of sections exposed in the recent road-widening operations between Taynuilt and Loch Awe, an opportunity was taken to re-examine the small outlier of Carboniferous rocks near the Bridge of Awe at the west end of the Pass of Brander (Geological Survey One-inch Map, Sheet 45). It was hoped also that the investigation would yield some points of comparison with the Carboniferous strata of Inninmore on the Sound of Mull (1). The Bridge of Awe sediments seem to have been first noticed by Macculloch in 1817 (2). The red colour of the beds and the fact that they outcrop in the midst of lavas of Lower Old Red Sandstone age led observers to regard them as belonging to the same formation. They were assigned this age in the ‘Summary of Progress of the Geological Survey for 1897’ (3), but in the following year Mr. D. Tait obtained from shales a little north of Bridge of Awe a few fragmentary plant remains which definitely proved the sediments to be Carboniferous (4). The accompanying sketch-map indicates the approximate limits of the outlier. It is largely concealed beneath alluvial deposits and the only sections are those exposed on the banks of the River Awe. The actual junction with the underlying lavas can be seen on the right bank below the bridge and at two localities on the left bank above it. The exposures above the bridge, however, can only be properly examined when the river is low. The writers were fortunate This 250-word extract was created in the absence of an abstract The authors desire to acknowledge the help given by Professor J. W. Walton and Dr. R. Crookall in the examination of material and the assistance of Mr. W. Manson in the field.

The Geology of the District around Llansantffraid ym Mechain, Montgomeryshire

The area to be discussed, lying to the south-west of Oswestry, Shropshire, is bounded on the north and east by Carboniferous and newer rocks. It adjoins on the south-west the Meifod area, described in 1928 by Professor W. B. R. King, and on the south the Welshpool area, dealt with by Dr. A. Wade in 1911. No detailed account of this district has previously been given, but all except the most southerly portion is included in sheet 137 (Oswestry) of the Geological Survey one-inch map, and described in the accompanying memoir (Wedd and others 1929). In the latter, references will be found to published earlier work. As a result of the present reinvestigation of the Llansantffraid district, the map (Pl. XXXIX), differs considerably from the solid edition of the Oswestry sheet. This is particularly so to the north of Llansantffraid, where Ashgillian rocks have been shown to outcrop over a considerable area previously mapped as Caradocian. The limestones south of Llansantffraid have been shown to be the local base of the Valentian. The object of this paper is to describe the stratigraphy of the Llansantffraid area, with particular reference to the zonal classification of the Upper Ordovician rocks and the nature of the Ordovician-Silurian boundary. Mr. B. B. Bancroft worked out a detailed succession in East Shropshire (1928 a , pp. 33–41), and claimed that a part of the same succession was present in the Caradocian rocks at Bala, Meifod, Welsh-pool and Glyn Ceiriog (1928 a , pp. 40–1; 1933, tables). It has been

Three Tectonic Problems of the Lulworth District: Studies on the Middle Limb of the Purbeck Fold

Of all the folds thrown up across the Chalk plains of North-West Europe during the Alpine orogeny, the most interesting and the most perfectly exposed is the Purbeck anticline. In the cliffs of the Dorset coast the sea has laid bare all parts of the structure, from the core or crestal region, through the vertical and overturned middle limb and the “foresyncline” (Busk 1929, p. 29), into the foreland, where the Upper Cretaceous rocks are seen reposing with sharp unconformity upon a previously folded and eroded Jurassic foundation. The general and some special aspects of the fold and its associated faults have been discussed in a previous paper (Arkell 1936). The present paper results from a study of the middle limb, where it is dissected by the sea cliffs of the Lulworth district. These cliffs have long been renowned for their beauty, but their marvellous tectonic features, both great and small, have been neglected, with the result that their value to students of tectonics has not been fully utilized. The first three parts of the paper attempt a solution of the three most outstanding problems : contortions in the Purbeck Beds, the Purbeck Broken Beds, and the abnormal attenuation of the strata towards Durdle Door. The fourth part offers an interpretative essay and synthesis. The area dealt with is included in sheet 342 of the Geological Survey one-inch map and sheet 141 of the Ordnance Survey one-inch map. The contortions in the Purbeck Beds at Stair Hole are illustrated in

Eclogites from the Neighbourhood of Glenelg, Inverness-Shire

I. Introduction. References to the occurrence of eclogites in the western Highlands of Scotland are singularly scarce. Teall (1891) described an eclogite from Totaig Ferry, Loch Duich, about 5½ miles north-east of the Kirkton of Glenelg, and he observed that the existence of such a rock in the British Isles did not appear to have been previously recorded. In the Geological Survey memoir which describes sheet 71 of the one-inch map (Clough and others, 1910) many references are made to the occurrence of eclogites and eclogitic rocks near Glenelg. As is explained in the memoir, no general attempt was made to map the margins of these rocks owing to their extremely complicated character. Many of the more important occurrences are described, however, and the areas in which such rocks are most abundant are indicated on the one-inch map. Although the chemical composition of none of the eclogitic rocks was determined, an analysis was made of a garnet from an eclogite near Beinn a' Chapuill. Reference to the occurrence of eclogites in the Lewisian is made by Harker (1932) and an example from Glenelg is figured. Eclogitic rocks have also been recorded from central Sutherland by Read (1931) and An Cruachan in central Ross-shire (Peach and others, 1913). The Glenelg area, in which the rocks here described occur, is shown in the eastern portion of the one-inch map, sheet 71, and is bounded in the north by Loch Alsh and Loch Duich, in the west by Kyle Rhea and the Sound

Tholeiite dykes of the Moorfoot Hills

The object of this paper is to describe a series of tholeiite dykes that occur in the south-western part of the Moorfoot Hills. These dykes cut Ordovician strata forming part of the Northern Belt of the Southern Uplands. They lie within Sheet 24 of the One-inch Geological Map of Scotland. In the ‶Explanation of Sheet 24″ (1869) James Geikie mentions the dolerite rocks in the Craighope Burn; and a number of the dykes are recorded on the original geological one-inch map. Field Characters. The dykes have their greatest development in the headwaters of the Leithen. Isolated examples are found in the Redscarhead Burn, 2½ miles north of Peebles; at Longcote, one mile E.S.E. of Eddleston and near the source of the Hope Burn which drains to Heriot Water. In every case where the dykes are seen in situ the trend is N.W.-S.E. The dykes in the Leithen Water occur about 1½ miles N.W. of Craighope. Within a distance of 400 yards, at least five dykes are found. Unfortunately, the presence of dykes is indicated chiefly by trails of blocks, many of them being of large dimensions. Only a few doubtful exposures are found of the rock in situ. There can be little doubt, however, that these blocks mark the actual positions of underlying dykes. The stream below the dykes contains few or no boulders, and this fact, coupled with the presence of sharp rocky bluffs along the stream banks, shows that ice movement in the upper reach of this valley

IX.— The Drummuck Group, Girvan; A Stratigraphical Revision, with Descriptions of New Fossils from the Lower Part of the Group

I. INTRODUCTION. The Drummuck Group as defined in this paper falls entirely within the one-inch Geological Map, Scotland, Sheet 14. It forms part of the succession in the Craighead-Glenshalloch inlier. This elongate, anticlinal inlier—which comprises all the Ordovician and Silurian beds north of the Girvan valley—consists of three main blocks:—(1) Craighead Hill; (2) Drummuck and Quarrel Hill; and (3) a less well-defined north-eastern block, entirely (Lapworth, 1882, Pl. XXIV) or partly (Geological one-inch Map, Scotland, Sheet 14) divided by faulting from the Drummuck and Quarrel Hill block. II. TABLE OF STRATA IN THE CRAIGHEAD-GLENSHALLOCH INLIER. The following table embodies the findings of previous authors (Lapworth 1882, Peach and Horne 1899, Jones 1928, etc.) and also additions proposed in the present revisory paper:— III. NOTES ON PREVIOUS RESEARCH. An early contribution to the reading of this succession was that by Murchison who distinguished an ascending series consisting of (1) lavas, (2) Craighead Limestone, (3) sandstone and conglomerate of Mulloch Hill, and (4) Drummuck shales (1851, pp. 143-146). Hugh Miller, while deferring to Murchison, was not quite sure that the Drummuck beds succeeded those of Mulloch Hill (1858, Everyman Edition, p. 299). The age and stratigraphical order of the beds were not settled until Archibald Geikie wrote a substantially correct summary interpretation (1869, pp. 8-10). It remained, however, for Lapworth, as part of his paper “The Girvan Succession,” to publish, in full detail, what is still the definitive account of the inlier (1882, pp. 614-621). In this paper, which is illustrated with This 250-word extract was created in the absence of an abstract In conclusion I wish to thank all who have helped me with advice or in the field. Professor E. B. Bailey and Dr. John Weir supervised the work while it was in progress, read the typescript of the paper, and made many suggestions. I also received assistance in identifying certain of the fossils from Mr. B. B. Bancroft and Mr. J. Shirley. Through the kindness of Dr. W. D. Lang, Miss Muir-Wood, Dr. H. Dighton Thomas, and Mr. T. H. Withers I received material from the South Kensington Museum for comparison with a number of the new Girvan species. In mapping and collecting I had the help at different times of Mr. J. L. Begg, Rev. J. M. Ewing, Mr. G. T. Smith, and others, to all of whom I am very grateful. Most of the field-work was done while the writer was in receipt of a Research Scholarship under the Carnegie Trust for the Universities of Scotland. My thanks are due to the Carnegie Trustees for this, and also for a grant towards the cost of illustrating the paper. I am further indebted to the Senate of Glasgow University for their award of a Strang Steel Scholarship, for the current session, during which the work has been completed. Mr. D. M. Filshill made the photographs for Plates VII and VIII.

Report of the Ordnance Survey

THE report of the progress of the Ordnance Survey for the year 1933 (H.M. Stationery Office. 3s. net) directs attention to the slow rate of revision in the field of the large-scale plans which is at present possible. During the last three years, revision has been largely confined to the area of Greater London, adjoining counties, Devon, Cornwall, parts of the West Riding and Manchester areas. But the greater part of England has not been revised for more than ten years and much is more than twenty years out of date. Wales and Scotland have been largely un-revised for at least twenty years. Progress is reported in the preparation of the new fifth or relief edition of the one-inch map, and six more sheets were published during the year. Archaeological maps of the Trent Basin and the Old Sarum district were published. Other publications included the magnetic edition of the physical maps of England and Scot land.

The Carnmenellis Granite: Its Petrology, Metamorphism and Tectonics

I. Introduction The Carnmenellis granite and its metamorphic aureole were mapped, in 1839, by de la Beche. The area has since been re-surveyed by the Geological Survey and the results recorded in the one-inch maps, nos. 352 and 359 (New Series) and in the Survey Memoir on the Falmouth and Camborne district (Hill & MacAlister, 1906). The granite is an important unit in the chain of post-Carboniferous granite intrusions forming the backbone of the peninsula of Cornwall and Devon. The consanguinity of these intrusions has long been known, but the recognition of the composite character of individual intrusions is comparatively recent. Intrusive relationship between major composite masses was observed on Dartmoor by the members of the Geological Survey (Reid & others, 1912), Brammall (1923), and Osman (1928), and on Bodmin Moor by myself (1927). Intrusion sequences are discussed by Brammall (1923 & 1932) and Osman (1928). Important petrological contrasts between the Devonian and the Cornish granites were pointed out by Flett and Dewey (Reid & others, 1912), and problems of variation within individual complexes have since been made the basis of detailed study by Osman with special reference to the Dartmoor and Scilly Isles masses, by Richardson (1923) dealing with the St. Austell granite, and by myself in a paper on the Bodmin Moor granite (1927), and the Carnmenellis granite, the subject of the present contribution. I would add that, subsequent to the presentation of the paper to the Society, I have had the advantage of re-examining my analytical data

The Pre-Cambrian and Lower Palæozoic Rocks of the Eastern end of the St. David's Pre-Cambrian Area, Pembrokeshire

I.Introduction This paper describes the geological structure of a strip of country lying between four and 12 miles east of St. David's, and occupying the central portion of the small peninsula of north-western Pembrokeshire. Although in a district made classical by the researches of many famous geologists, this tract has received but passing notice, and, up to the present, has remained practically unknown geologically. The area is about 30 square miles in extent, measuring rather more than seven miles from east to west and four miles from north to south. It is bounded on the east by the G.W.R. main line to Fishguard, where the line runs along the Western Cleddau valley, between Welsh Hook and Mathry Road (Heathfield). On the north it adjoins the Abereiddy-Abercastle area (Cox, 1915, p. 273) and the Pen Caer area (Cox, 1930, p. 274), while to the south is the Brawdy-Hayscastle area (Thomas & Jones, 1912, p. 374). The St. David's area (Green, 1908, p. 363) and the Trefgarn area (Thomas & Cox, 1924, p. 520) lie respectively a few miles to the west and south-east. The country here described is represented on the Ordnance Survey six-inch quarter-sheets, Pembrokeshire 15 N.E., S.E., N.W., S.W., 16 N.W., S.W., 8 S.E., and 9 S.W., and it comprises a portion of the area embraced by the Geological Survey one-inch maps, Sheet 40 (Old Series) and Sheet 209 (New Series). The district forms part of the Pembrokeshire 400-foot peneplain, and shows the monotonous topography typical of the in

Changes in Land Utilization in the South-West of the London Basin, 1840-1932

T HE Land Utilization Survey has set out to record how the surface of the country is being used at the present time, and the information, obtained by volunteer workers and recorded on the six-inch maps of the Ordnance Survey is being made available for study through its publication (by the Ordnance Survey) in the form of one-inch Land Utilization maps, giving in colours over the ordinary map a precise picture of the landscape pattern. This article is an attempt to consider one aspect of the work, that of the value of the present record for purposes of comparison with conditions at other periods. Those who, in the future, wish to examine the changes which will have taken place between our period and theirs, will have our record available for consultation. They will be able to see exactly where changes have taken place, and with the material at their disposal will be able to assess accurately the factors which have influenced and controlled changes in some areas, or which have resulted in a stability of conditions in others. We, who examine the cultural landscape of the present day, the state which is always about to change itself into the future, are less fortunate when we wish to look backwards in order, by examining the past, to understand more fully how the present landscape has been evolved, since we have no easily accessible records of land utilization in the past. There are some, of course, such as William the Conqueror's Survey, and the manorial maps, but the former is of little use since it was not recorded in map form, while the latter are often difficult to reproduce on a scale which would make them comparable with current maps, and moreover they were not made in large numbers at any one particular period. There are several valuable surveys at later dates, such as Rocque's, but they are not of widespread occurrence. Our best data for the past exist in a survey made nearly a century ago for the purpose of tithe commutation. The survey was made on a parish basis, a plan being made, with each plot of ground numbered and a schedule drawn up, which gives, among other particulars, the utilization of each field. The greater part of the data relates to the period I839-40-41, and by examining the records it has been possible to construct land utilization maps of certain parishes for that period. The Ministry of Agriculture, in whose possession the records are kept, has been good enough to allow access to the documents for this purpose. The procedure which has been adopted has been to choose certain parishes in the area to the south-west of London, and to make for them a one-inch Land Utilization map for the period about 1840, which is strictly comparable with the published one-inch Land Utilization map of the Windsor area (sheet I I4). To ensure accuracy, the tithe maps have first been reduced to the six-inch scale, the scale on which the field work of the present survey has been carried out, and then reduced to the one-inch scale. In some areas it was necessary to use the first as well as the second editions of the six-inch sheets in order to identify former fields, so great have been the changes in the landscape. In other more rural areas the arrangement of the fields, etc., has remained much the same,

Revision of Ordnance Maps

IN the report of the Progress of the Ordnance Survey for the year 1932-33 (London: H.M. Stationery Office, 1933. 3s. Qd. net), attention is directed to the difficulties and delay in revision of the sheets owing to financial restrictions. The reduced staff available for field work on large-scale plans means that revision has to be limited, more and more, to areas completely altered or built over since the last edition of the sheet. Field work thus tends to become original survey and the time needed for each sheet increases. While the yearly output of 25-in. plans was more than two thousand in 1923, it has now fallen to about seven hundred. In the earlier year the number of man-days spent in the field upon the revision of one 25-in. sheet was about eleven; it is now about fifty-two. The delay is thus progressive as time goes on, and has already become very serious. Since the revision for the one-inch sheet is based on large-scale plans, the new edition of small-scale maps is seriously impeded. Whereas in 1913 a one-inch reviser could do 96 square miles per month in open country or 40 square miles in close country, he can now do only 18 per month in country round London. Nevertheless, the new relief edition of the one-inch map is making steady if slow progress.