designated by a proper hydrographical survey, the questions of local water supply will be reduced, in each case, to an elementary simplicity. The remark previously hazarded to the effect that a great nation which is contented to remain in general ignorance of those physical conditions of its own country of which the knowledge is essential to its welfare, is hardly entitled, ad hoc, to be called civilised, recurs to the mind with increased force when we observe how we have up to this moment neglected to draw up a hydrological survey of the country. Our youngest sister among the great European Powers may here well put us to shame. Before she was, as a nation, three years old, Italy had turned her attention, by the agency of her Minister of Public Works, to the hydrographic features and changes of the country. The important cases of the Tiber, the Po, and the Brenta, each received the careful study of a separate commission of men of the first eminence in civil or in hydraulic engineering. Nor was the Minister content with the simultaneous execution of tasks for the like of which the Thames, the Severn, the Shannon, and other of our own rivers have so long made very costly appeals to the deaf commonsense of both Government and people. The Italian Department of Public Works is zealously preparing a hydrological survey of the whole of peninsular and insular Italy. More than a hundred of the principal rivers and torrents have already been accurately surveyed; and the whole mass of knowledge thus attained, tabulated and co-ordinated, has been published for the benefit of the country. What was done in the case of the Po may give some idea of the thoroughness with which the Italian Government have set themselves to learn the facts, so as to be able to A supply the needs of the case. topographical survey of the entire basin of the river, on a scale of 1 400,000' 400,000 forms the groundwork of the survey. A plan, on a scale of eight times that magnitude, of the banks and shores of the river has been added. Sections have been taken and plotted of the branches and mouths of the river, and of the principal embanked affluents, as far as the influence of the backwater of the Po is felt. A main section, or profile, of the river has been drawn, on the scale of horizontal and vertical. Eightynine cross-sections have been taken across the embanked part of the river, which extends from Pavia to the sea; and above 200 diagrams have been prepared, showing the daily observations of the principal hydrometers which have been erected along the embanked portions of the river. In preparing these plans each bank of the Po for its entire course was independently levelled. The length of the section on the right bank is 350 miles 600 yards; that on the left bank is 349 miles 441 yards. The sections show the altimetric determination of every beach mark, the crests of the banks, the flood highwater lines, the levels of the meadows, the lowest levels of the summer flow, and the maximum and mean depths of the river. It is thus within the competence of the engineers forming the commission for the survey of the Po to tell, with very close accuracy, how much of, and in what manner, the entire rainfall of the great watershed of the Po makes its way to the Adriatic. To men furnished with this information, the nature and magnitude of the works demanded for the improvement and maintenance of the river channel become a matter of simple investigation. It has been determined to spend 600,000l. in restoring and strengthening the banks of the Po, and a further sum of 320,000l. in subsidiary works. A law was passed in July 1876 assigning a sum of 280,000l. for the execution of the first series of these works. We are not in possession of the materials for forming an estimate, but venture to suggest that the actual damage inflicted by the floods to the dangers of which the dwellers in the Valley of the Thames, especially those residing in South London, are now left to reconcile themselves, may in a single year amount to no small portion of the outlay requisite to make safe the course of the Po for at least the third of a century. In Rome, works of a more imposing magnitude are in progress, in order to give the citizens that protection from the Tiber which it does not seem to be the duty or the care of anybody to give to London from the Thames. The bottom of the river is to be reduced to a regular inclination of 1 in 2,500; and a channel 109 yards in width is to be enclosed between two river walls rising 55 feet above the zero mark on the hydrometer of the Ripetta. The sum of 220,000l. has already been allotted to the execution of the works. The yet more serious question of the filling up of the lagoon of Chioggia in consequence of the diversion of the river Brenta is yet under anxions investigation. Surveying work of this nature, there is no room to doubt, is the first requisite towards a solution of any problem respecting the water supply of England. The proposition, indeed, needs only to be stated. Its truth is incontrovertible. Advice is required from the engineer. He ought to offer none, and if he does his duty, either to his employers or to himself, he will offer none, until he is in possession of the facts. To demand a hydrological survey only means that all the facts of the water supply and of the water discharge of the country must be ascertained and recorded in a clear and exact form. To a certain extent this may be accomplished in distinct detail. An accurate knowledge, for example, of the hydrology of the Lake district might not be indispensable to the wise ordering of the hydraulic arrangement of the Thames Valley, except in the case (which is by no means an imaginary one) of a project to decant the water of the lakes for the supply of the metropolis. But what is really indispensable is, that the full particulars of every river basin and watershed district should be ascertained before any important works affecting the hydraulic conditions of any portion of that district are taken in hand. The first step, therefore, towards the returning of an intelligent reply to the question raised so opportunely by His Royal Highness the Prince of Wales is the division at all events on paper-of England into hydrological districts. Something of the kind has, indeed, already been suggested, and to a considerable extent acted upon, by Mr. Symons. In the annual report on British rainfall published by that gentleman, to which reference has before been made, the island is divided into ten registration divisions, which are almost identical with those adopted by the Registrar-General of England and Scotland. However convenient this division may be for many pur poses, it is not, however, suitable to that now under review. Mr. Symons' first division, for example, comprising Middlesex, forms only a portion of the great natural province drained by the confluent rivers Thames and Medway. This province must be studied as a whole,. or, to say the least, under their two watershed divisions. Portions of four or five of the registration divisions are comprised in this natural province. Running through a district covered by tertiary and alluvial strata from the sea as far up as Reading, the Thames is formed at that spot by the confluence of two streams, either of which has some title to be called the parent of the river. According to the usual geographical rule, which assigns to the stream of longest course from its origin the dignity of parent, the Thames rises from the oolite hills of Gloucestershire in a place called the Seven Springs, near Cirencester, at a distance of a little more than 200 miles from its mouth. This gives a total annual water supply over the entire district of 9,431 milliards of metric tons of water. How much of this large quantity escapes to the sea through the channels of the Medway and of the Thames is unknown. How much escapes from the surface of the soil by evaporation is unknown. How much seeks a subterranean channel towards the sea, through the pervious strata of the cretaceous and neocomian systems, is unknown. The striking the balance of this great physical account is the first desideratum for the engineer. What he does observe, roughly speaking, is, that to supply 50 metric tons of water per head to each inhabitant of the district requires an annual supply of 250 millions of metric tons of water; and that in order to obtain that quantity he must, in some way or other, impound nearly two and a half per cent. of the rainfall. The problem, therefore, does not seem to be one of insuperable difficulty. Yet it is by far the most unmanageable case which is to be found within the area of the Kingdom. If we regard chiefly the topographical and geological features of the district drained by the Thames, we should call the Kennet, rising in the cretaceous hills near Chippenham, the parent stream. The character of the river scenery, and of the geological incidents which give their stamp to the landscape, continue in this direction; while on approaching Oxford the country assumes a very different aspect, as the river flows through the liassic and oolitic formations. The Medway, while piercing the great cretaceous rampart which stretches from Farnham to Dover, has its cradle in the neocomian strata of Surrey; from which also the Wey, the Mole, and the Wandle convey their tributes to the Thames. It is probable that a far larger quantity of water than the latter rivers carry down flows beneath the soil, through the greensand or other pervious strata, towards the line of the Thames Valley ontfall; being then stopped by the great fault that runs approximately in the line of that valley under part of London, and escaping underground to the sea. The course of the Medway is about 75 miles in length. The basin drained by these rivers covers, on a rough approximation, an area of some six thousand square miles, and contains about five millions of inhabitants. The average rainfall, as far as it can be ascertained from Mr. Symons' valuable data, is 24:56 inches for an average year. If we turn our attention to the northern counties, we shall at once become aware how different are both the hydrological and the economical conditions there from those which prevail in the watershed district of the Thames; nor can we fail to note how essential is the need of a special study of the hydrology of the island, province by province. The tenth registration division of Mr. Symons contains the four northern counties, Northumberland, Cumberland, Durham, and Westmoreland. The hydrological surveyor will adopt a different principle of division. The watershed areas of the Tyne, the Wear, and the Tees, drain into the North Sea. Springing from the ridges of the Millstone Grit, and lower carboniferous limestones, these rivers, with smaller parallel streams, run through districts covered with the coal measures and the poicilitic strata to the south of their outcrop. Lying in Northumberland, Durham, and part of Yorkshire, the district is 'characterised by rapid rivers, by deep clefts in the country, which here and there is traversed by basaltic dykes, and by an outfall at once more copious and more independent of any aid to main arterial drainage than occurs in other parts of the country.' This eminently natural province covers an area of about 3,000 square miles. The aggregate length of the three rivers named is stated at 200 miles. The rainfall, calculated as before described, attained the high average, for England, of 4117 inches. The population may be taken at a million and a half. The supply of water, on these data, amounts to 7,904 milliards of metric tons in the year; and it does not require one per cent. of this volume to supply every inhabitant with a weekly allowance of a metric ton. That portion of the rainfall of the northern registration district of Mr. Symons which descends to the westward of the lofty water-parting line of the lower carboniferous range of hills is poured into the Irish Sea through the channels of the Ribble, the Lune, the Eden, and some parallel streams. The Silurian rocks make their appearance in this province, as well as the mountain limestone, the coal measures, and the poicilitic beds. There we have the very healthiest part of England; the death-rate of Westmoreland is only 1783 per mille, that which most nearly approaches it, viz. 1794 per mille, being found in Rutlandshire. The density of the population attracted by the coal beds of Cumberland, increases the mortality of that county to 32:18; which is still below the average for England. 1 British Quarterly The lake country presents us with a knot of mountain peaks and valleys, of which Scafell, Skiddaw and Helvellyn are the primates, the abundant rainfall of which is pent up in a beautiful series of tarns, meres, and lakes, and finds its issue to the sea in every direction but an easterly is one. The scenery of this part of England The that of the Alps on a small scale. But scale is not readily applied to landscape, except by the toil of the pedestrian. From the top of Skiddaw a varied and beautiful panoramic view is commanded which is calculated to impress on the observer the wide difference displayed by the physical character of the country within a small topographical range. The swelling peaks of the Yorkshire moors near Whitby, the bold bluff of Ingleborough, the clouded summit of Snowdon, the cleft peaks of stations that tell of moor and waste. Criffel, are so many mountain telegraphic cultivated banks of the Derwent look like a garden divided into innumerable flower beds, and dotted with fairy-like houses. Man lies cradled in the Irish Sea, and as a presage of unusually bad weather may be seen, by a sort of Fata morgana, even from the banks of the Solway north of Carlisle. That legend haunted frith, backed by the long ridge of Criffel, lined with houses that gleam like batteries against the rising from Skiddaw. On either side stretches a sun, has a remarkable fivefold appearance broad band of gold-coloured sand, fringed by a dark line of turbid water; while in the very midst of the channel the fresh-water stream of the Solway glitters like a thread of silver.' The area of this district, which forms the tenth of our natural watershed provinces (of which the eastern portion of the same registration district forms the first), is about 2,500 square miles. The rainfall, in the absence of more recent measures of distribution, must be taken at the same depth as in the eastern province, viz. 41°17 inches; giving a water supply of 6,587 milliards of metric tons. The popu lation is about a million and a half. Their requirements of water will make a demand of about one and a quarter per cent. on the assumed rainfall of the district. It will be observed that round numbers alone are here used, except in the case of the inches of rainfall, Review, No. cxv. p. 48. which are the actual mean figures obtained from grouping the observations of Mr. Symons. Greater accuracy is, at present, hardly possible, owing to the fact that none of the sources of information attainable apply to conterminous districts. It is probable, for instance, that a larger share of the water that is attracted by the great range of mountain limestone hills falls on the western than on the eastern district. But in order to ascertain how far that is the case, the rainfall stations must be grouped together according to the particular watershed districts to which they respectively belong. Again, the number of these stations should bear a definite relation to the area of the country. Violent falls, such as that as the Styehead Pass, are strictly local. In order to ascertain how much the attraction of any particular mountain, such as Scafell Pike, contributes to the water supply of the country, it is necessary to measure the area over which such a disproportionate precipitation takes place. In a word, the stations which the engineer will demand, in order to be furnished with elementary data for ascertaining local or general water supply, must be selected and determined on scientific principles. As to the observations which we actually possess, and which depend on the unpaid and deserving care of so many private individuals, their localities depend on what we call chance. Thus it is probable that by the use of round figures we not only point out the fact that the estimates now put forward are rough and provisional, but we come, in all probability, as close to the truth as it would be possible to do if we spoke in more precise figures. Again, with reference to the population; the figures given by the Registrar-General which have been taken as the basis of our estimate, refer to the parochial, union, or other political divisions of the island, not by any means to its physical divisions. Thus by attempting to show, by way of example, a forecast of results that can only be exactly obtained by the means of such a survey as that for which it is the object of the writer to plead, the work done is only that of the pioneer. Topographical distribution, arranged according to the hygrometrical features of the country, is necessary for the determination of the locality of those points of observation at which the leading facts required for the truth of the survey have yet to be ascertained. With this reserve, it may be pointed out that the natural watershed provinces of England and Wales appear to be ten in number. Of these we have spoken of the first, the fourth, and the tenth. The second comprises that large area which the two long streams of the Ouse and the Trent combine to drain into the estuary of the Humber. The source of the Swale, the northernmost main feeder of the Ouse, is in the mountain limestone ridge near Richmond. Streams flowing from Warwick, from Wolverhampton, from Newcastle-underLine, and from Macclesfield, form affluents of the Trent. The Don, running past Sheffield, only misses a confluence with the Trent by falling a little westward of that river into the Humber. An approximate measurement of the area of country thus drained (which will probably prove under the mark) makes it amount to 9,400 square miles. Cretaceous, neocomian, oolitic, liassic, poicilitic, and carboniferous strata, give their several and special characters to various districts of the main outfall provinces. The savage grandeur of the Peak looks down on its centre (as to its northward and southward extent), forming a bulwark to its western boundary. The average amount of its rainfall, taken as before mentioned, is 30.88 inches. It is probable that an ex |