Hydrology of South Africa; or Details of the former hydrographic condition of the Cape of Good Hope, and of causes of its present aridity, etc

Front matter

Preparing for the Press, JWPJrJWFT J J* fF/W = OR, RECORDS OF THE REPLANTING OF THE ALPS, THE CEVENNES, AND THE PYRENEES, WITH TREES, HERBAGE, AND BUSH, WITH A VIEW TO ARRESTING AND PREVENTING THE DESTRUCTIVE CONSEQUENCES AND EFFECTS OF TORRENTS. Compiled by JOHN CROUMBIE BROWN, LL.D. ; OR DETAILS OF THE FORMER HYDROGRAPHIC CONDITION OF THE CAPE OF GOOD HOPE, AND OF CAUSES OF ITS PRESENT ARIDITY, WITH SUGGESTIONS OF APPROPRIATE REMEDIES FOR THIS ARIDITY. COMPILED BV JOHN CROUMBIE BROWN, LL.D., Formerly Government Botanist at the Cape of Good Hope and Professor us Botany in the South African College, Capetown, Honorary Vice-President of the African Institute of Paris, Fellow of the Royal Geographical Society, Fellow of the Linnean Society, <Lx. HENRY S. KING & CO., 65 CORNHILL, and 12 PATERNOSTER ROW, LONDON. 1875.

ALL RIGHTS RESERVED. CONTENTS AND ARGUMENT, PAOK Preface, 1 Introduction 7 States how the subject of the Hydrology of South Africa came under the consideration of the Author , gives his experience of drought at the Cape (p. 8) ; and of deluges (p. 12); and observations ofthe similarity of several districts to features ofthe Lake Districts of North America and of Finland (p. 14).

Part I

— Former Hydrographic Condition of South Africa, IS Chapter I. — Testimony supplied by the Physical Geography of South Africa, ....... 18 Describes the general contour of South Africa (p. 18) ; specifies at greater length similarities to features of the Lake Districts of North America and to Finland (p. 21) ; adduces indications that the land had been long under water, and that valleys specified had been created by the flow of ocean-currents (p. 27) ; describes the composition of Table Mountain (p. 31) ; aud draws the conclusion from the physical geography of the locality that the land must have upheaven from the bottom of the ocean, and, it may be, have been again submerged and subsequently upheaven, and this done oftener than once (p. 33). Chapter II. — Testimony in regard to the former Geographical condition of South Africa supplied by Geological Observations, 35 Section I. — Geological Formations of Table Mountain, 37 States that these belong to the Primary, Metamorphic, Silurian, and Devonian formations (p. 38) ; supplies indications of the land having been for ages of untold duration at the bottom of the ocean (p. 47) ; and quotes descriptions given by Hugh Miller of what may be supposed to have then been the state of the ocean (p. 57).

Section II. — Geological Formations less ancient than those qf Table Mountain, ..... 6*2 Refers successively to the lower and upper karoo shales, with imbedded fossils, indicative of the existence of dryland (p-62) ; to trap conglomerate rocks, indicative of volcanic eruptions (p. 64) ; and dicynodon fossils, indicative of the existence of extensive lakes— quotes description given by Hugh Miller of the supposed condition of land at this period (p. 68), and description given by Page of coal deposits (p. 69) ; cites account given by Dr Grey, of Cradock, of carboniferous deposits in the vicinity of dicynodon beds (p. 75) ; and refers successively to new red sandstone formations (p. 78), ooletic formations (p. 80), tertiary deposits (p. 82), boulder formations (p. 85), and the drying up of the Great Sahara (p. 88). contents.

PASE Chapter III. — Indira/ions of the former Hydrographic condition of the country supplied by Arborescent Productions found in the interior of South Africa, .... Describes groups of olive trees, accacias, and baobabs, seen beyond the Colony of the Cape of Good Hope (p. 95) ; and states how information in regard to the desiccation of the country might be obtained from sections of such trees (p. 97). 93 Chapter IV. — Hydrographic condition qf tlie country within the historic period. ..... 102 States what time may be considered as embraced by the historic period (p. 102) ; cites observations made by Moffat, by Livingstone, and by Chapman (p. 104) ; and conclusions drawn by Fox Wilson in regard to the progress of desiccation (p. 108) ; and concludes with the intimation that, in regard to the former hydrographic condition of the country, we have indications of a progressive desiccation having gone on from the last emergence of the land from beneath the ocean up to the present day, producing as a result the existing condition of aridity of climate and of soil (p. 113).

Part II

— Cause or Occasion of the Desiccation of South Africa, . . . 114 Chapter I. — Primary and Principal Cause of the Desiccation and consequent Aridity of South Africa, 114 Reference being made to the phenomena of elevation and subsidence throughout extensive areas of the earth's surface (p. 115) ; there are cited indications of South Africa being, or having been, within a period not very remote, upheaven from a lower level (p. 115), including the phenomena of the cataracts ofthe Shire (p. 118), the rapids of Kebrabasa (p. 119), the Makololo valley (p. 123), and the Victoria Falls of the Zambesi (p. 125) ; and indications of extensive upheavals having occurred in other lands— including Great Britain (p. 131), and the Continent of Europe (p. 133), and of upheaval and subsidence going on throughout an extensive area of the Southern Ocean (p. 134).

The theory generally adopted in regard to these phenomena is explained (p. 137) ; and objections to it are met (p. 139). Section II. — Application of this as a Hypothesis to the Geological Phenomena and Physical Geography of South Africa, 145 It is shown to fit in with these as does a key with the wards ofa lock in regard to dykes and faults (p. 145), with the indications of a progressive depression of the ocean-bed beyond, supplied by the island of St Helena (p. 147), with the inclined position of layers of clay-slate at base of Table Mountain (p. 149), the thickness ofthe geological strata in South Africa (p. 151); and the removal of large portions of these by ocean currents (p. 152) ; and illustrations of what has occurred in the upheaval of South Africa are supplied from what is going on in other lands (p. 153), hot springs and subterraneous rivers indicate the flow of the water by other courses (p. 154) ; there are cited indications ofthe existence of subterraneous rivers and subterraneous reservoirs of water in other lands (154), and of the existence of such in South Africa (p. 155) ; and it is stated that to water being carried off by superficial and subterraneous watercourses may be attributed primarily and principally the desiccation of South Afriea (p. 157). Chapter II. — Secondary Causes of the Desiccation ami consequent Aridity of South Africa, . CONTENTS. V

Section I

— Phenomena of Evaporation, and Modifications of this produced by Atmospheric Moisture and by Shade, . , 158 Evaporation is referred to as a terrestrial phenomenon, extensively manifested (p. 158), diminished by atmospheric moisture (p. 159), and by shade (p. 160) ; and illustrations are given ot effects produced by the destruction of trees' and by sylviculture, in St Helena (p. 161), and by the destruction of forests elsewhere (p. 163). Section II. — Denudation of South Afiica by Destruction of Herbage and Trees, ...... 167 There is adduced testimony that the destruction of herbage and trees has been carried on from former times to the present (p. 167) ; there is described the effects on forests at the Cape of Good Hope of the reckless destruction of these (p. 171) ; and details are given of the destruction of these at different times bv fire (p. 175).

Section III. — Effects of Denudation of the Country on Evaporation, 1 94 These effects, in accordance with experiments cited, are stated to be the promotion of evaporation of moisture from the soil (p. 194) ; the consequences of this are shown by quotation of statement by Mr J. F. Wilson, on the desiccation or diminution of the water supply in the basin of the Orange River (p. 197), with remarks on the same by Dr Livingstone, and by him by Sir Roderick Murchison, Dr Kirk, Mr Galton, Colonel Bafour, and Lord Stratford de Redcliffe (p. 204), and corresponding testimony by Dr Rubidge and by Mr J. H. Davis (p. 207). Section IV. — Effects of Denudation of ihe Country on the Rainfall, 208 It is stated that one effect produced by forests is a comparatively equable destribution of the rainfall over time and space (p. 208) ; testimony of meteorologists and others to this fact are cited (p. 209) ; and illustrations of the irregularities of the distribution of the rainfall in South Africa are adduced (p. 211).

Section V. — Effect of Denudation of ihe Country on ihe Hydroscopicity qf the Soil, ...... 213 Reference is made to the effect of vegetable mould in attracting moisture from the atmosphere (p. 213) ; testimony is adduced to show that such soil is decomposed by sun-light and then losses this property (p. 214) ; and soil deprived of covering is liable to be washed away by the rain and blown away by the wind (p. 214).

Part III

— Aridity and Water Supply of South Africa, 216 Chapter I. — Aridity and Water Supply beyond the Colonized portion of South Africa, ...... 216 Section I. — Aridity beyond ihe Colonized portion of South Africa, This is illustrated by accounts given by Dr Livingstone of his experience at Kolobeng (p. 216), by the great sufferings of Mr Helmore and his family in the interior (p. 217), and by accounts given by Mr M'Kenzie, of Shoo3hong, (p. 222). 216 Section II. — Water Supply in regions beyond ike Colonized portion of South Africa, ...... 223 Contains account given by Bakwains to Livingstone, Oswell, and Murray (p. 224) ; notices of the Congo (p. 224), of the plains of the Lobele (p. 224), and ofthe plains of Leeba (p. 225). VI CONTENTS.

P/VOR Chapter II. — Aridity and Water Supply within the Colony of the Cape of Good Hope. ..... 227 The aridity is illustrated by the freezing of water near Hopetown, (p. 227) ; and water supply by an enumeration of alternate droughts and deluges that have occurred since 1863, with details of deluges and floods committing devastations at Port Elizabeth, (p. 229) ; and other parts of the Colony in 18G7, (p. 232) ; at Natal in 1868, (p. 234); Capetown and the adjacent districts in 1869, (p. 238); at Beaufort in 1870, in Victoria West, 1871, (p. 241) ; at Capetown, 1872, and in various parts of the Colony at the breaking up of the drought in 1874, (p. 244); information is supplied in regard to the natural history of hail storms, called forth by report of a hail storm in connection with this, which otherwise might have been thought incredible, (p. 245) ; the accounts of the breaking up of the drought is resumed (p. 249) with a summary of the damages done, estimated at about £300,000, (p. 251), and an account of similar damages done at Bloomfontein, in the Orange River Free State, (p. 251), a reference is made to the contrasts (p. 252); and the Chapter concludes by a picture given liy Moffat (p. 253).

Conclusion, 258 It is stated that corresponding accounts might be given of the hydrology of other lands, (p. 2.i8), and that appropriate remedies are the erection of dams to prevent the escape of a portion of the rainfall to the sea ; the abandonment or restriction of the burning of the veldt ; the conservation and extension of existing forests, (p. 259) ; and the adoption of measures similar to the reboisement and gazonnement carried out in France, with a view to prevent the formation of torrents, and the destruction of property occasioned hy them. INDEX TO AUTHORITIES CITED. ADAMSON, page 99. Alexander, 172. Allan, 91. Ansted, 73. Asbjoernsen, 209. BABBAGE, 100. Baden Powell, i. Bain, 19. Balfour, 207. Barber, 170. Barrington, 175. Barth, 209. Bazalgette, 228. Belgrand, 209. Belknap, 29.

Preface

. This Volume owes its publication in some measure to the phrase Postal University having come under my notice in a passage in a review, wliich appeared in the Spectator, of a work by Mr George Baden-Powell, entitled " New Homes for the Old Country," of which the following is an extract : — "The squatters or landed proprietors of Australia are mainly drawn from the highest class of immigrants, and have generally received some, at least, of the elements of a liberal education ; but they enter, many of them, on their new work very young, and rind themselves at certain seasons of the year with ample leisure, but, as Mr Baden-Powell remarks, separated by their new life from all the centres of learning : " ' Could they but bridge over this separation by means of the post, they might continue to do a modified amount of work on some useful subject.

A Board of professors forms the centre of the system, and all the instruction is carried on by letter. The idea might further be elaborated into examinations, and even to the granting of degrees. Peculiarly and immediately useful woull be the study of engineering, and of veterinary seiencs, of natural history, of law, and many other matters of immense benefit to the dwellers in the bush. And a young " super," by devoting any leisure hours, more especially of his first three or four years, to the study of veterinary science, would assuredly become a far better manager of cattle, sheep, and horses, than if his knowledge of the subject were confined to limited personal experience. _ The value of runs, again, is greatly enhanced by the proper storage of water, by the erection of dams, anil by judicious clearing and planting.

For such purposes engineering, geology, and botany, practical and to the point, may prove of immense use. In short, many are tlie branches of knowledge which might be successfully studied by the means of such instructors, and which in the end would prove invaluable to the success ofthe squatter. A postal university might be made to form an efficient substitute for training colleges, which would be of little use in a country where the requisite amount of leisure time at the disposal ofthe would-be students is so broken anil uncertain that their attendance would be an impossi bility, even though we leave out ofthe question altogether the immense distance they would have to journey to any fixed centre. Heading by post could be carried on at any available opportunity, and at any distance from the central courts.' " In connection with this it is said : — ■ " Sydney possesses a University of its own, at which, however, at present, it is impossible to get that real University education whose chief charm lies not so much in the book-learning that it gives as iu that mutual intercourse and rubbing together of those of every character with learned, clever, and good men, which proves so useful iu after life.

New South Wales, though fortunate iu possessing the services of several clever professors, is as yet too young to provide a sufficiently large number of undergraduates. "Situated on the top of a neighbouring eminence, the University Buildings form a conspicuous and handsome feature ia the Sydney landscape, and closer inspection will show them to be of very high order with regard to size, plan, material, aud finish. " The happy idea of starting what may be called a Postal University has lately claimed attention. Such method of education should prove an immense boon to Australia. Thousands and thousands of miles of bush country are held by the squatters, and their work, necessarily of a very isolated character, is mainly in the hands of young men, most of whom have entered on its life fresh from school and full of aspirations. At times they have a great amount of leisure ou their hands, and this a large majority of them would probably be very glad to devote

PREFACE.

. to self-improvement. At school their minds have been trained ; thus they know the way of working, but their new Use separates them from all centres of learning." Such was the statement of Mr Baden-Powell. On seeing this I addressed to the editor of the Colonies a letter on the subject, of which the following is the substance : — " The term Postal University is new to me, but the desideratum is not. For some years I held the chair of Botany in the South African College, Capetown, aud iu professional tours which I made throughout the colony and districts beyond its limits, I met with not a few meu such as are referred to, giviug thought in their isolated homes to the requirements of the country for the development of its resources aud its capabilities, and giving willing labour to the perfecting of devices which could ouly be entertaiued iu ignorance of what was well known to practical and scientific men iu Europe.

" On some of the tours which I made, I gave field-lectures ou the vegetable products of the locality, which were attended by numbers varying from fifteen to eighty ; and not a few availed themselves of the opportunity thus afforded to them to propound questions of considerable importance to the interests of the colony — questions relating not only to economic botauy, but to mining, to metallurgy, to motive force developed in connection with magnetism aud electricity, aud to other subjects. "On other tours I encouraged arrangements being made for opeu public conferences on subjects connected with agriculture, arboriculture, aud irrigation. These were attended by still greater numbers ; and information was given and obtained on a wide range of subjects. On oue occasion, at an isolated farm, Borne twelve or fifteen miles from Montague, from twenty to thirty farmers met me, and the conference was continued, with a Bhort intermission for refreshments, from 10 a.m. till 5 p.m. At these conferences there occurred sometimes an adjournment in a body to the vineyard, the water leading, or the dam, for the purpose of testing information given, and continuing the discussion in view of facts and phenomena referred to.

" Subjects broached at the field lectures and conferences were discussed more fully in letters, which were franked at the Colonial Office. Copies of these letters were appended to annual reports to the government which 1 made as Colonial Botanist. These were printed and submitted to both Houses of Parliament, by commaud of the governor, and a number of copies were put into circulation on loan, while copies were sent to officials and others, who might desire to possess copies for reference. "The following list of these shows the kind of subjects upon which information was sought : — "Appended to Report of Colonial Botanist for 1863— (1) Memoir on the Conservation and Extension of the Forests as a means of counteracting disastrous consequences following the destruction of Bush and Herbage by Fire.

(2) Report on the Capetown Botanic Gardens. (3) Copies of Letters to and from the Colonial Botanist on subjects connected with the Development of the Resources of the Colony, viz. : 1. Letters from and to the Rev. T. D. Philip Hankey on Destruction of Orange Trees ; 2. Letter to the Rev. P. Small, Bathurst, on the Rust in Wheat ; 3. Letter, sent in triplicate, to A. N. Ella, Esq., Queen's Town, F. Xf\ Hopley, Esq., Burgersdorp, and D. Arnot, Esq., Colesberg, on (Jrasses and Pasture Herbs ; 4." Letter to J. Mosel. Esq., Uitenhage, on the possibility of obtaining a substitute for india- Rubber or Gutta-Percha from the Milk Sap of the Euphorbia; 5. Letter lo W. Lemark, Esq., Port Elizabeth, ou the Growth of Chicory ; 6. Letter to Mr Titterton. Kracha Kama' on the Cultivation of the Prickly Pear, with a view to the Preparation of Cochineal ; 7.

Letter to the Rev. T. Merrington, Bethelsdorp, on the Cultivation of the Soccotrine Aloe, and the Preparation ofthe Drug; 8. Letter to Mr Buckley, Knysna Forest, on the Cultivation of the Olive and Kei Apple; 9. Letter to the Rev. W. Stegmann, Adelaide, on the Spread of the Rhenoster Bush; 10. Letter to Mr Hayward, Swellendam, on tbe Planting of Trees by Water-Courses ; II. Letter to the Rev. J. Brownlee, King William's Town, on Plants fouud by him in British Kaffraria; 12. Letter to Dr Harvey, Professor of Botany, Trinity CoUege, Dublin, on South African Plants; 13. Letter to John A. Merrington, E<_q on Irrigation, Arboriculture, Wine-Making, the Utilization of Night-Soil, and the Collecting of tialt as supplying Remunerative Employment for Capital. PEEFAOE. III Appended to Report of Colonial Botanist for 1864.- (1) Letter to J. A. Merrington Esq London, on the Sour, the Sweet, and the Mixed Veldts, and the Karoo, on their Agricultural Capabilities, and on the Employment of Irrigation, Arboriculture, Agricultural Machinery, and Manure, as means of developing these.

(■<:) Letter to the same, iu answer to the question -Can we increase the number of Vegetable Productions of South Africa, or can we render those already obtained more valuable?— including notices of Lindseed Oil, Colza Oil, Mustard Chicory, Beet Tobacco, Wine, Euphorbia Sap, Aloes, Timber, Maize-Fibre Olives, Castor Oil, Myrtle-Berry, Wax, Keurboom Gum, Buchu, and Indigo. (3) Letter to the same, on the improvement of the manufacture of Cape Aloes. (4) Letter to the fame on the preparation of Ebonite and Vulcanite from the milk sap of the Euphorbia. (5) Letter to the same on the improvement of the Cape Wines. (6) Letter to the same, on the importance of the establishment of an experimental farm, with a view to ihe development of the agricultural resources of the Colony. (7) Letter to J. H. Davis, Esq., J.P., Colesberg, on brasses and Herbage found on the Sour, the Sweet, and the Mixed Veldts, and the Karoo.

X* ,% t0 "■ W* HoP17' Es1-< M.L.A., Burghersdorp, sent in duplicate to A. N. Ella, Esq., yueens lown, on Pasture Herbs and Grasses of the districts of Albert and Queen's Town. 9) Letter to John Dickson, Esq., Port Elizabeth, on Grasses adapted to arrest drifting sands. (10) Letter to F. Tudhope, Esq., Graham's Town, on the question— Whether good or evil preponderates in the results obtained bv burning the veldt ? embodying an illustration of the improbability of the pastoral condition of the Colony being perpetuated by the practice. (11) Letter to Dr Harvey, Professor of Botany, Trinity College, Dublin, on South African Plants. (12) Letter to James Chapman, Esq., Cape Town, on tne Welwitschia mirabilis. (13) Cir cular addressed to Missionaries labouring in South Africa beyond the Colony, requesting their co-operation in extending the acquaintar ce of botanists with the flora of South Africa.

(14) Report on the accommodation provided for the herbarium of the late Dr Pappe, and on the expediency of providing accommodation for a museum of South African Vegetable Economic Products. (15) Letter to the Honourable the Colonial Secretary on measures calculated to develope the vegetable resources of the Colony. " Appended to Report of Colonial Botanist for 1865.— ( i) Letter to G. A. T. de Graaff, Esq., Hon. Secretary to Mosael Bay Agricultural Society, on Experimental Farms adapted to the wants of the Colony. (2) Report on the Potato Disease, submitted in accordance with the desire of Select Committees of Legislative Council. (3 ) Report on Rusts and other destructive growths on Cereals. (4) Report on the Destruction of Orange Trees in the Colony, with special notices of the Scale, the Soot-like substance, and the Ants and other Insects found upon diseased Orange Trees, and of the probable cause of the evil, and the remedy.

(5) Report on the Destruction of Chesnut Trees and Walnut Trees in different parts of the Colony. (6) Report on the Blight affecting Apple Trees in the Colony. (7) Letter to E. V. Williams, Esq., Simon's Town, on the affection of Peach Trees. (8) Letters to Albert Kennedy, Esq., Land Surveyor, Humansdorp, on the arrest of Drifting Sand, and on planting the same with Trees, (9) Letter to J. F. J. Wreusch, Esq., Sec. to Divisional Council of district of Albert, on Trees deemed suitable for culture in that and similar districts. (10) Letter to J. H. L Schumann, Esq., Aberdeen, South Africa, on Trees deemed suitable for culture in the Karoo and Sweetveldt, and on raising Trees from Seeds. (11) Letter to E. L. Layard, Esq., Cape Town, on Trees deemed suitable for culture at Cape L'Agulhas and other districts exposed to a strong sea breeze.

(12) Letter to Dr Mueller, Government Botani3t and Director of Melbourne Botanic Gardens, relative to Shrubs and Trees used at the Cape for Fences, Avenues, and Burying-grounds. (13) Letter to Walter G. Fry, Esq., Victoria Tanery, Bristol relative to Tannin-yielding Plants growing in the Colony. (14) Letter to D. D. Williamson, Esq., Manager of the North British Rubber Company, Edin burgh, on the utilisation of Milk-sap of the Euphorbia. (15) Letter to the Rev. Mr Rousseau, Clanwilliam, on the Culture and Manufacture of Indigo. (16) Circular relative to facilities for Irrigation in different parts of the colony. Appended to Report of Colonial Botanist for 1866.— (1) List of South African Trees, Shrubs, and Arborescent Herbs — upon the natural history, or botanic characters, or economic uses of whicti a report is forthcoming if necessary.

(2) Abstract of memoir prepared on the Forests and Forest Lands of Southern Africa. (3) Abstraci of memoir prepared on lhe Forest Economy of the Colony. (4) Abstract of memoir prepared on Arboriculture in the Colony. (5) Ab stract of memoir prepared on the Hydrology of Southern Africa. (6) Abstract of memoir prepared on Irrigation, and its application to agricultural operations in South Africa. (7) Observations on the agricultural capabilities of the Colony, and requirements for the development of these : A resume* of the results and observations made during tenure of office in the years 1863, 1864, 1865, and 1866. (8) Copy of circular relative to South African Plants de sired by the Directors of Botanic Gardens in Europe and elsewhere. " Such are subjects on which information has been desired and transmitted by post in one colony, and it may be inferred that corresponding information will be desired in others.

" The desideratum might be supplied in part by the publication of a series of treatises on discoveries of modern science applicable to the development of colonial settlements, printed in small type and on thin paper, that they

PREFACE.

. IV may be transmitted by book-post from the place of publication if need be to wherever they may be required. In such treatises it would be desirable that all statements in other works cited should be quoted in full, as those for whose perusal they are designed live far from cities, have not access to works of reference, and rarely have au opportunity of entering a bookseller's shop. " More efficiently would the desideratum be supplied if arrangements were also made for answering queries. This might easily be done by combining with the publication of such treatises as have been referred to the publication of other works calculated to meet the craving of colonists having little access to general literature, issuing the whole periodically, keeping each number within a specified postal weight, and bringing each up to this by appended sheets appropri ated to answers to correspondents, and by encouraging subscriptions for the whole by annual pre-payment by post-office orders.

There is not an outstation to which letters can be sent to which these could Dot be sent from London, the postage being substituted, if necessary, for the trade allowance to book sellers. " In the absence of any such arrangements, may I submit to your consideration tbe expediency of making the Colonies a medium for such communication ? What I attempted to do single-handed lit the Cape might be done much more efficiently and extensively by the editor of a newspaper or periodical extensively circulated in the colonies, published in London, where access could be had to sources of valuable information on subjects connected with the practical application of science to the physical development of nature. I do not conceal from myself that it would be unreasonable to expect that professional counsel would always be obtained by the conductors simply for the asking ; and I question whether any increase of circulation which would result from arrangements for obtaining infor mation from professional men ou all subjects, on which information might be desired, would cover the expenditure which would be incurred in procuring this.

"This is one of the considerations on the ground of wliich I would recommend the publication of treatises with the provision for answering queries." Practical effect has not been given to the suggestion, nor is it deemed probable that it would be found remunerative to do so ; but it may be some one may be able to give a practicable and remunerative form to the idea suggested to me by the proposal of Mr Baden-Powell ; and having had of late some time at my command, I have, partly with a view to supply an indication of the kind of treatises which I consider to be likely to meet the case of such colonists, of the character described by him, with whom I have had correspondence or personal intercourse, recast the materials I had collected on the Hydrology of Southern Africa and embodied in the Memoir on that subject referred to above, in which the desiccation of South Africa from pre-Adamic times to the present day is traced by indications supplied by geological formations, by the physical geography or general contour of the country, and by arborescent productions in the interior, with results confirmatory of the opinion that the appropriate remedies are irrigation, arboriculture, and an improved forest economy ; and in recasting this I have added information which has in the interval come into my possession.