have done anything like equal justice to the subject, and the generous devotion which Mr. Judd has shown in giving so much valuable time to our work, after he

ceased to be a member of the Survey, deserves the most grateful acknowledgment.

ANDREW C. RAMSAY,

13th March 1875.

Director-General.

TO THE DIRECTOR GENERAL OF THE GEOLOGICAL

SURVEY OF THE UNITED KINGDOM.

SIR,

Geological Survey Office, 28, Jermyn Street, London, S.W.,

20th February 1875.

THE Country comprised in Sheet 64, which takes in the whole of the county of Rutland, was surveyed by Mr. J. W. Judd, between the years 1867 and 1871.

This Map is of special interest as being the first published by the Survey upon which the limestone, that was formerly considered to be a part of the Great Oolite, has been referred to its true position in the geological scale as a member of the Inferior Oolite, to which the distinctive name of Lincolnshire Oolite was assigned by Mr. Judd, from its great development in that county.

When Mr. Judd left the Survey, on the completion of his fieldwork connected with the above area, he disinterestedly consented to write the Memoir in explanation of the Map; and the present important work is the result of his labours.

In it, besides giving a detailed description of the geological structure of the district, Mr. Judd has discussed at length the more general and purely scientific questions connected with the subject, and has explained the grounds upon which the conclusions were founded that led him to propose an entirely new and altogether original nomenclature and classification for the Oolitic rocks of the midland district of England, which have been since accepted by the Geologists of this and other countries.

Mr. Judd has been aided by Mr. Etheridge in the preparations of the tables shewing the geographical and stratigraphical distribution of the fossils and in the palæontological portion generally. Several views of oolitic scenery have been contributed by Mr. Rutley from sketches made on the ground.

Mr. Whitaker has also assisted in the bibliographical portion; and Mr. Holloway has rendered valuable help in constructing and drawing illustrative geological sections, as well as generally in passing the work through the press.

I have the honour to be,

Sir,

Your obedient servant,

HENRY W. BRISTOW,

Director for England and Wales.

To Andrew C. Ramsay, Esq., LL.D., F.R.S.,

PREFACE.

IN obedience to a very general demand for the more rapid completion of the maps illustrating the coal-producing districts of the country, the officers of the Geological Survey of Great Britain, who were employed in tracing northwards the boundaries of the Jurassic Strata, were nearly twenty years ago transferred to the northern counties.

Thus the mapping of the Lias and Oolites remained during considerable interval in abeyance. This period was, however, marked by many important advances made by geologists in their knowledge of the rocks in question, and by the introduction of new principles and methods of classification. The views gradually elaborated by Quenstedt, Fraas, Marcou, Oppel, and others on the continent, were applied by Dr. Wright and other geologists to the rocks of this country, and the necessity for modifications of the classification, adopted in some of the former publications of the Survey, were thereby rendered manifest. In particular, we may mention the conviction arrived at by many geologists, that certain rocks supposed to be of Great Oolite age, ought in fact to be classed with the Inferior Oolite.

Having been engaged during six or seven years in preparing a geological map and description of that interesting county-so little known to geologists Lincolnshire, I had been gradually led to the adoption of the views referred to above; and in 1867, when it was determined to resume the mapping of the Jurassic rocks, I was requested to join for a time the staff of the Geological Survey, and to devote my attention to the country intermediate between Lincolnshire and the districts already mapped. It soon became clear to me that not only would the doubtful beds have to be classed with the Inferior Oolite, but, that, in consequence of the very local character of many of the formations in the district, a new classification and nomenclature was rendered absolutely necessary in order to adequately represent them.

During several years I was employed in working out the details of this question and in mapping the most critical portion of the district; and in 1870, after the results which I had arrived at had been examined and approved by the responsible officers of the Survey, the new classification was published in the Index, and a little later, in sheet 64 of the Survey map. I then examined the country to the southwards, revising the maps already published and preparing new editions of them.

This task completed, my connexion with the Survey ceased, and my attention was directed to entirely new fields of geological inquiry. On its being pointed out to me, however, that the want of a memoir, explaining the grounds of the classification which I had originated, would be productive of inconvenience, I undertook to write the present work; the form assumed by which has been, to some extent, determined by the peculiar circumstances under which it has been prepared.

Questions of an exclusively scientific nature, such as those involved in the methods of classification adopted, are discussed in the Introductory Essay; while subjects of general and local interest, in connexion with the district more especially described, are treated of, in large and small type respectively, in the second part of the volume. The circumstance that the work has been written in the intervals snatched from many other occupations and studies, may not perhaps be accepted as any apology for imperfections and inequalities in its mode of execution, but it must be pleaded as an excuse for the delay in its completion.

Fortunately, however, geologists have not been compelled to await the appearance of this volume for an illustration and defence of the classification and nomenclature of the Jurassic rocks in the Midland district, now employed by the Survey; for, not only has my friend MR. SAMUEL SHARP of Dallington entirely adopted these views himself, but he has chivalrously maintained and ably exemplified them in two memoirs read before the Geological Society, a task for which his extensive knowledge of the rocks and fossils of the district eminently fitted him.

During my execution of the survey of the area, I received much valuable assistance, not only from MR. SHARP, but from many other local geologists, among whom I may especially mention MR. BEESLEY of Banbury, the REV. MILES J. BERKLEY, formerly of King's Cliffe, MR. BIGGE of Islip, MR. BENTLEY of Stamford, and the late DR. PORTER of Peterborough. While