Chapter III: Part 3

Large sums of money had already been expended by the general government in local improvements, but no consistent plan had been developed that would be an acceptable guide in conducting operations along the whole river, when this act went into effect. It is not necessary to refer here to the various systems that were presented to the Commission for consideration; nor to enter upon the details of the plan finally adopted; our record being more the effects and primary causes, than the intermediary processes through which the results have been produced. The general plan followed by the Commission has been the construction of works in the bed of the river, to form new banks where a contraction of the river bed has been deemed necessary; and the erection of levees, with grading, revetment, and other protection of the banks, in localities where the natural banks seem particularly liable to give way under the pressure of a great flood. The object of such works being to control the river by confining the low water channels in fixed lines, causing the recurrence of the scour in low water stages in the same channel in successive low waters; and preventing the diversion of the stream into new channels during high water stages by overflow of the banks. A diversion of the stream would leave the works in the bed of the river below of no greater value than as monuments to the energy and skill displayed in the details of their construction, and preclude the ultimate benefit that may be derived from these works in permanently lowering the bed of the river. The probability of such diversion of the water, however, seems to have been reduced to a minimum, through the conservative action of the Commission in coöperating with the States having jurisdiction over the alluvial bottoms, in reorganizing their levee systems and thus securing the greatest control over the volume of water brought down in the flood seasons, that is possible by the construction of well planned and substantially built levees. It having been demonstrated that the levees subserve a double purpose, that they are essential in the general plan to improve the navigation of the river adopted by the Commission, and are likewise needed to render the bottom lands habitable, it is not surprising that we find the State authorities and the Commission jointly engaged in their construction.

It has thus been brought about that the effort to improve the navigation of the river for the general welfare, has resulted in such great changes in the geography of the locality, that a large district has been reclaimed for agricultural purposes. The alluvial valley of the Mississippi river has an area of thirty thousand square miles, and is naturally divided into four great basins that have been designated the St. Francis, Yazoo, Tensas and Atchafalaya. Two of these basins are now fairly protected from the overflows of the Mississippi, by the levees that have been constructed, or repaired, incidental to the work of the Commission, viz: the Yazoo basin extending from below Memphis to the mouth of the Yazoo river; and the Tensas basin from the high land south of the Arkansas river to the mouth of the Red river; and the Atchafalaya basin, from the Red river to the gulf, has been protected on the Mississippi fronts. These three basins have an aggregate area of nearly twenty thousand square miles that is now reasonably secure from inundation. Measures have also been instituted by the State authorities looking to the reclamation of the St. Francis basin; and the work is half accomplished on the White river section.

Nearly the whole of this valley was under protection thirty years ago, but the disasters of the late civil war, and subsequent inability of the people to repair the damaged levees, resulted in the practical abandonment of many sections, and it was not until about ten or twelve years ago that the protective works again presented an appearance of continuity. The supposed security, however, was of short duration, as the great floods of 1882 overtopped the works in more than one hundred and forty places, causing such widespread destruction that cultivation of the soil was rendered impossible over large districts. The floods of succeeding years but added to the misfortunes of the valley, and land values became so depreciated that sales were impracticable, taxes could not be collected, and there was a general feeling that square miles of fertile land must be given over to the destructive agencies of the great river that had made it.

It was while suffering under this distressing situation that the work of the Mississippi River Commission was brought forward as a possible means of salvation. With a recuperative power that seems almost marvelous, the people have contributed of their labor and their means, until now this great area of nearly twenty thousand square miles has been once more reclaimed, and seems to have entered upon an era of prosperity that will eclipse the prophecies of even the most sanguine. It is believed that the levees that have now been constructed will prove reasonably secure. They have been built for a double purpose; and the proportion of the expense incurred by the general government, about one-third, under the direction of the Commission, has insured a supervision and inspection by competent engineers such as was not exercised in the earlier history of such works on the river.

We cannot foretell the developments that will follow the improvement of this water way and the reclamation of the alluvial bottoms on an enduring basis. That the works erected by the Commission will maintain an increased depth of water at the low stages of the river, seems to be demonstrated, as during the low water of November last a depth of nine feet was found on the Lake Providence and Plum Point bars, an increase of thirty-three and forty-four per cent. respectively. When the depths on the other bars have been increased in like proportion the free navigation of the river will be assured, and we may point to the result as one of the greatest engineering achievements of modern times.

The increased value of the land adjacent to the river redeemed from waste, more than doubled on the average, and in many instances quadrupled; the replenishing of the state and county treasuries by the collection of taxes on land that was before unremunerative; and the building of railroads through sections where it had been impracticable to maintain them before in consequence of their liability to destruction by the periodic floods; are marked evidences of the material prosperity that has already followed the great work. During the last four years, forty thousand settlers have taken up lands in the Yazoo basin alone, and it was estimated that in the fall of 1889 twenty thousand more would seek homes in the same district. These settlers have been mostly negroes from the worn out high lands to the eastward. If the change in their environment proves beneficial to the individual we may expect an increased migration, that may in turn be an aid in solving the political problem involved in the citizenship of the negro.

The settlement of these bottom lands will also influence the prosperity of many commercial centers, as trade statistics indicate the general abandonment of the plantations that followed the great floods of 1882, caused a marked diminution in the shipments by the lower river, as well as in the receipts from that section; and that the partial reclamation of the lands and restoration of agricultural pursuits has already influenced the receipt and distribution of commercial products.

The project to reclaim by irrigation large districts of the arid region of the west, if successfully accomplished, may also exert an influence in the political and commercial relations of the future that cannot now be foretold. Two-fifths of the territory of the United States has been classed as arid; not in the sense that there is no water, for the greatest rivers on the continent have their sources almost in the midst of the region; but rather that the water is not available for enriching the ground. The rainfall is generally not in the season when the crops would require it, or is too small and uncertain for the husbandman to depend upon it. The whole region is not of this character; many districts are susceptible of the highest cultivation as nature has left them, and others have been redeemed by the application of the water supply through the simpler devices customary in irrigated countries; until now nearly all the districts have been occupied that are susceptible of agricultural pursuits, either in the natural state or by irrigation, unless water is secured by means generally beyond the reach of the individual or combination of individuals who may use it. And yet, it is believed there are millions of acres of rich land that may be redeemed and converted to the support of a large population, by the application of capital in the construction of works of irrigation. The progress of the surveys of the region, therefore, that have been instituted by the general government, are watched with absorbing interest. The districts susceptible of such extensive improvement are only approximately known, and as it is only through these surveys their availability will be made manifest, the importance of the work can hardly be overestimated. The prosperity of several states will be largely influenced by the success of operations of this kind within their borders, and in turn their greater development and increased wealth, must react upon the older communities and benefit them, on the principle that the healthful growth of a single member is strength to all.

The science of geography, as taught in the present day, is more comprehensive than the brief descriptions and delineations of the areas of land and water that satisfied the early explorers. The great strides that have been made in scientific research during the past century have opened new fields, and men are no longer content to picture that only which they can see. The varied features of the earth's surface, transformations now in progress and those which may be deduced from the facts we can observe, have led to many theories of the construction of the earth, ancient forms upon the surface and possibilities, if not probabilities, in the future. To ascertain the form of the earth has alone been the cause of heroic labor, and yet we have hardly passed the point that we can give it in probable terms with the general dimensions. Observations warrant the assumption that, discarding the accidents of nature--even the highest mountains--the sphere is far from being perfect. That it is flattened at the poles is now accepted as the true condition, but we have reason to believe, too, that this is not the only departure from the perfect sphere. The more thorough the research and precise the observations, the more certain does it appear that the crust has a form as though there had been great waves of matter that had been solidified. To locate the depressions of these great waves and measure their depths, to point to the crests and measure their extent, is a problem for the future to solve. Their study is claimed to be within the legitimate sphere of geography; and not until they have been satisfactorily answered can we assert the geographer is even approaching the end of the facts his science has yet to utilize.

In pre-historic geography we have had two papers presented to the Society during the past year, relating to the orographic features of the earth's surface in times past compared with the localities as we may see them to-day. In the first instance the comparison is evolved from an effort to trace the origin and growth of the rivers of Pennsylvania; and the second, in a description of the famed district around Asheville, North Carolina. These have a substantial interest to us, treating as they do of localities so well known; and they illustrate, too, the resources of induction in bringing to our view the probable wonders of ancient geographic forms.

The constitution of the interior of the earth is a subject of great interest in the science of geography, as many of the visible forms upon the crust have been wrought by the power of the agencies within it. The discussion has been warm in the past, and doubtless will be resumed with unabated interest as we find new phenomena for the argument. The apparent lull that has followed the promulgation of the theory, three years ago, that under the crust we should find a fluid, or semi-fluid, surrounding a solid nucleus, may not be of long duration. This hypothesis probably comes nearer to satisfying the conditions imposed by the physicist and geologist, than those which have preceded it, and may be accepted for the present; unless the processes of nature by which it is conceived this state of the interior of the earth has been produced, shall be demonstrated to have continued for sufficient time to have caused a condition of equilibrium and possible solidification of the whole sphere; when we might expect it to be repudiated by those who oppose the theory of isostacy, but commended by the physicists as supporting their claim that the earth must be substantially a solid even now. If we accept Mr. Frederick Wright's suggestion, isostacy may have an important bearing on the cause of the ice sheets that covered such great areas; a suggestion that opens to the vision of the imagination an orography beside which the grandest landscape we may see to-day would pale into insignificance. This is believed to be a new application of the isostatic theory, and may be a possible solution of a much vexed question when an initial cause for such great upheavals can be advanced that will not be inconsistent with other accepted conditions.

Theories are modified by new facts, and in any attempt to demonstrate the constitution of the interior of the earth, the increase of temperature with the depth is an important factor. The recent measures, therefore, in Germany, that indicate the figures generally accepted are not reliable, may be received with interest. The shaft was sunk especially for the purpose of observing temperatures at different depths, and every precaution that former experience had suggested seems to have been taken to secure accuracy. The greatest depth reached was about one mile. An elaborate discussion of the results fixes the increase of temperature at 1° F. for each 65 ft. increase of depth. This is about 15 ft. greater than the figures that have heretofore been given; a difference so large that we may question if they will be generally accepted until verified by further observations made with equally great care.

In conclusion permit me to note the fact that the United States was for the first time represented in the International Geodetic Association, at the meeting recently held in Paris; and also to record the successful conclusion of the fourth International Geographical Congress that assembled in Paris in August last. The reports from the Congress indicate a wide range of subjects discussed, and lead us to believe the interest in our science is progressive, and must receive the hearty appreciation of all who are inspired by the nobler instincts to develope the great sphere on which we live; that the riches, the beauties, and above all the grandeur of Nature, may be made manifest to ourselves and for our posterity.

REPORT--GEOGRAPHY OF THE AIR.

BY GEN. A. W. GREELY.

It is with a feeling of increased responsibility, shared doubtless by the Presidents of other sections, that the Vice-President of the Geography of the Air brings before you his modest annual contribution in one branch of geographical science.

We live in an age so imbued with earnest thought, and so characterized by patient investigation, that an eager gleaner in scientific fields finds at the very outset his mind filled with the garnered grain of golden facts. The more cautious searcher often follows with uncertain mind, and doubtless in his backward glances sees many fairer and heavier sheaves than those he bears with full arms, from the fruitful harvest. If, then, you do not find here dwelt on such geographical phases as you judge most important, attribute the fact I pray you, not to neglect, but to lack of observation, or to the exercise of an undiscriminating judgment.

First let us turn to the higher class of investigations, wherein that handmaid of science, a true and noble imagination, comes to supplement exact knowledge, to round out and give full form and perfect outline, either shaping a number of disjointed and apparently heterogeneous facts into a harmonious series, or evolving from a mass of confusing and seemingly inexplicable phenomena a theory or law consistent therewith.

In this domain Professor Ferrel's book on Winds is probably the most important theoretical meteorological discussion of the past year. It owes its value to the fact that it puts into comparatively simple and popular form the processes and results of his intricate mathematical investigations of the motions of the air, published by him years since, and later elaborated during his service with the Signal Office.

In connection with the subject of winds, Professor William M. Davis has formulated an excellent classification, depending first, on the ultimate source of the energy causing the motion; second, on temperature contrasts which produce and maintain winds; and third, on their periodicity and the time of the first appearance of the motion.

Professor Russell, appropriately it seems to me, remarks regarding the landslide winds, that avalanche would be a better term than landslide as applied to winds associated with fallen masses of earth or snow.

With the enormous amounts of accumulated tabulated matter, and numerous studies bearing on isolated meteorological phenomena, it is a specially important consideration that some students pay constant attention to the investigations of the laws of storms. From such researches definite advances in theoretical meteorology may be made and fixed laws determined, which may be of practical utility with reference to the better forecasting of the weather. In the United States Signal Office, Professor Abbe has brought together the results of his studies and investigations for the past thirty years, under the title, "Preparatory studies for Deductive Methods in Storm and Weather Predictions." This report will appear as an appendix to the annual report of the Chief Signal Officer of the army. Professor Abbe finds that the source and maintaining power of storms depend on the absorption by clouds of solar heat, and in the liberation of heat in the cloud during the subsequent precipitation, which, as he endeavors to show, principally influences the movement of the storm-centre.

In this method one takes a chart showing current meteorological conditions, and the permanent orographic features of the continent; lines of equal density are also drawn for planes at several elevations above sea-level. On these latter, and on the lines of the orographic resistance, are based intermediate lines of flow, which show where conditions are favorable to cooling and condensation. The amount of condensation and its character, whether rain or snow, are estimated by the help of the graphic diagram. Numbers are thus furnished that can be entered on the chart and show at once the character of the new centre of buoyancy, or the directions and velocity of progress of the centre of the indraft and the consequent low barometer.

It is hoped that this work of Professor Abbe's may be, as he anticipates, of great practical as well as theoretical value. Steps are being taken to test the theoretical scheme by practical and exhaustive applications to current work.

Tiesserenc de Bort has continued his work, of improving weather forecasts for France, by studying the distribution of the great and important centres of high pressures, which prevail generally over the middle Atlantic ocean, and, at certain periods of the year, over Asia, Europe, and North America. His studies have proceeded on the theory that the displacements of centres of high pressure, whether in Asia, over the Azores, near Bermuda, in North America, or in the Polar regions, set up a series of secondary displacements, which necessarily cause storm centres to follow certain routes. M. de Bort concludes that a daily knowledge of the relation of these centres and their areas of displacement will eventually enable skilled meteorologists to deduce the position of unknown and secondary centres. He has endeavored to reduce these various displacements to a series of types and has made very considerable progress in this classification. Daily charts covering many years of observations have been prepared, and these separated, whenever the characteristics are sufficiently pronounced, into corresponding types. This plan of forecasting necessitates extended meteorological information daily, which France obtains not only from Russia, Algeria, Italy and Great Britain, but, through the coöperation of United States, from North America. The daily information sent by the Signal Office shows, in addition to the general weather over the United States and Canada, the conditions on the western half of the North Atlantic ocean, as determined by observations made on the great steamships, and furnished voluntarily by their officers to the Signal Office through the Hydrographic Office and the New York Herald weather bureau.

The study of thunder storms has received very elaborate and extensive consideration. M. Ciro Ferari in Italy finds that almost invariably the storms come from directions between north and northwest, the tendency in northern Italy being directly from the west, and in the more southern sections from the northwest. The velocities of storm movements are much greater from the west than from the east, considerably more so in the centre and south of Italy than in the north; and in the months, largest in July.

The velocity of propagation increases with greater velocities of the winds accompanying the storms, with also greater attendant electrical intensity. The front line of propagation while more often curved, is sometimes straight and sometimes zigzag, and appears to undergo a series of successive transformations, more or less affected by the topographical nature of the country passed over.

Ferari thinks their principal cause is to be found in high temperatures coincident with high vapor pressures. Thunder storms, he considers, are essentially local phenomena, superposed on the general atmospheric phenomena. A principal general cause of thunder storms in Italy is the existence of a deep depression in northwest Europe, with a secondary depression in Italy dependent on the first. This secondary feeble area remains for several days over upper Italy, and nearly always is followed by thunder storms. Minimum relative humidity precedes, and maximum follows a storm, while the vapor pressure conditions are exactly reversed. Ferari notes, as one matter of interest, the passage of fully developed thunder storms from France into Italy over mountains 4,000 metres (13,000 feet) in elevation.

Dr. Meyer, at Gottingen, has investigated the annual periodicity of thunder storms, while Carl Prohaska has made a statistical study of similar storms in the German and Austrian Alps. The latter writer thinks they are most likely to occur when the barometer is beginning to rise after a fall, thus resembling heavy down-pours of rain.

In connection with Schmucher's theory on the origin of thunder storm electricity, Dr. Less has been able to satisfactorily answer in the affirmative an important point in the theory, as to whether the vertical decrement of temperature is especially rapid. Less finds evidences of very rapid decrement of temperature during thunder storms, as shown by the examination of records of 120 stations for ten years.

Mohn and Hildebrandsson have also published a work on the thunder storms of the Scandinavian peninsula. The rise in the barometer at the beginning of rain, they agree with Mascart in attributing largely to the formation of vapor and the evaporation of moisture from rain falling through relatively dry air.

A. Croffins has discussed thunder storms at Hamberg from observations for ten years. He believes that all such storms are due to the mechanical interaction of at least two barometric depressions.

As a matter of interest bearing on the much discussed phenomena of globular lightning, an incident is recounted by F. Roth, where a man feeding a horse was struck by lightning and lost consciousness. The man states that he felt no shock, but was suddenly enveloped in light and that a ball of fire the size of his fist, traveled along the horse's neck. This points to the fact that "ball" lightning is probably a physiological phenomenon.

In view of the recent extended interest in the question as to whether the climate of the United States is permanently changing, it should be remarked that this question has lately been under consideration with regard to Europe. Messrs. Ferrel, Richter, Lang, Bruchen and others conclude, from an examination of all available data, that there is no permanent climatic change in Europe. In connection with this discussion in Europe, long series of vintage records, going back to the year 1400, have been used. Apart from the ocean borders, extensive simultaneous climatic changes occur over extended areas, which changes--as might be expected--are more accentuated in the interior of the continents. These changes involve barometric pressure, rainfall and temperature, which all recur to that indefinite and complex phenomenon--the variation in the amount of heat received by the earth. The idea is advanced that these oscillations have somewhat the semblance of cycles, the period of which is thirty-six years. It may easily be questioned, however, in view of the fragmentary and heterogeneous character of the data on which this assumption is based, whether the error in the observations is not greater than the range of variation. Blanford, in one of his discussions, has pointed out that the temperature or rainfall data in India can be so arranged as to give a cycle with a period of almost any number of years, but, unfortunately, the possible error of observation is greater in value than the variations.

As to the United States, it is pertinent to remark that the Signal Office is in possession of temperature observations in Philadelphia, covering a continuous period of one hundred and thirty-two years. The mean annual temperature for the past ten years is exactly the same as for the entire period.

There have been criticisms in years past that the climatological conditions of the United States have not received that care and attention which their importance demanded. Much has been done to remedy defects in this respect, although, as is well known here in Washington, the general law which forbids the printing of any works without the direct authority of Congress, has been an obvious bar to great activity on the part of the Signal Office. Within the year the rainfall conditions of twelve Western States and Territories have been published with elaborate tables of data and fifteen large charts, which set forth in considerable detail the rainfall conditions for that section of the country. In addition the climatic characteristics of Oregon and Washington have been graphically represented; and rainfall maps,--unfortunately on a small scale,--have been prepared, showing for each month, the average precipitation of the entire United States, as determined from observations covering periods varying from fifteen to eighteen years.

In Missouri, Professor Nipher has prepared normal rainfall charts for that State, unfortunately on rather a small scale. In New York, Professor Fuertes, and in Michigan, Sergeant Conger, of the Signal Service, have commenced maps showing, by months, the normal temperatures of their respective States on maps of fairly open scale. Work of a similar character has been carried on in Pennsylvania under the supervision of Professor Blodget, well known from his climatological work. In other directions and in other ways, work of a similar character is in progress.

Without doubt too much is anticipated from pending or projected irrigation enterprises in the very arid regions of the West. These unwarranted expectations must in part result from a failure on the part of the investors to consider the general question of these enterprises, in its varied aspects, with that scientific exactness so essential in dealing theoretically with extended subjects of such great importance.

Everyone admits the correctness of the statement that the amount of water which flows through drainage channels to the sea, cannot exceed the amount which has evaporated from adjacent oceans and fallen as precipitation on the land. Further it is not to be denied that the quantity of water available in any way for irrigation must be only a very moderate percentage of the total rainfall which occurs at elevations _above_, and perhaps it may be stated _considerably above_, that of the land to be benefited.

Elsewhere it might be appropriate to dwell in detail upon the importance of cultivated land in serving as a reservoir which parts slowly with the water fallen upon or diverted to it, and in avoiding the quick and wasteful drainage which obtains in sections devoid of extensive vegetation or cultivation; and also that water thus taken up by cultivated lands must later evaporate and may again fall as rain on other land. But the pertinence of meteorological investigations in connection with irrigation and this annual address, relates much more directly to important questions of the manner by, and extent to which, precipitation over the catchment basins of the great central valleys fails to return in direct and visible form, through the water courses, to the Gulf of Mexico.

The inter-relation of rainfall and river outflows is one of peculiar interest, in connection with the important matter of irrigation now under consideration in this country.

Probably more attention has been paid to this subject in the valley of the Seine, by Belgrand and Chateaublanc, than in any other portion of the globe. One of the curious outcomes of Chateaublanc's observations, is one bearing on the maximum value of the floods in the Seine for the cold season, from October to May, by which he says that the reading of the river gauge at Port Royal is equal to 12.7 minus the number of decimetres of rainfall which has fallen on an average throughout the catchment basin during the preceding year. This curiously shows that the intensity of the winter floods of the Seine is inversely proportional to the quantity of rain of the _preceding_ year.

Sometime since, John Murray, Esq., in the Scottish Geographic Magazine, treated generally the question of rainfall and river outflows. The annual rainfall of the globe was estimated to be 29,350 cubic miles, of which 2,343, falling on inland drainage areas, such as the Sahara desert, etc., evaporate. The total annual discharge of rivers was estimated at 7,270 cubic miles. In the case of European drainage areas between a third and a fourth of the rainfall reaches the sea through the rivers. The Nile delivers only one thirty-seventh of the rainfall of its catchment basin, while tropical rivers in general deliver one-fifth.

The Saale river of Germany, from late data based on 45 rainfall stations in its catchment basin, during the years 1883 to 1886, discharged 30 per cent. of its rainfall.

During the past year Professor Russell, of the Signal Office, has determined carefully the rainfall and river outflow over the most important part of the United States, the entire catchment basin of the Mississippi river and its tributaries. This work was done as preliminary to formulating rules for forecasting the stage of the water several days in advance on the more important of the western rivers in the United States. The river outflows at various places on the Mississippi and Missouri and Ohio rivers, were tabulated from data given in the reports of the Mississippi and Missouri River Commissions. The tables were largely derived from the results of the measurement of current velocities. As gauge readings were taken at the time of discharge or outflow measurements, the discharges or outflows can be told approximately at other times when only the river gauge readings are known. The results for the outflow of rivers derived from measurements made under the supervision of these commissions, are of a high order of accuracy, and it is not probable that the results deduced from the gauge readings are much in error. Of 1881 and 1882, during which years measurements were made, 1881 was a year of great flood in the Missouri river, while the Mississippi river was not flooded. The year 1882, on the other hand, was marked by a great flood in the lower Mississippi river, with a stage in the Missouri much above the average. The rainfall in the six great valleys of the Mississippi, during the entire years 1881 and 1882, was charted from all observations available, and its amount in cubic miles of water calculated with the aid of a planimeter.

In connection with this investigation, and as a matter of value in showing the forces which are in operation to affect the river outflow, the fictitious or possible evaporation of the six great valleys referred to were calculated, in cubic miles of water, from July, 1887, to July, 1888, and also the average amounts of water in the air as vapor, and the amount required to saturate the air in the same valleys during the same period.

During the year 1882, the year of great flood in the lower Mississippi valley, the outflow at Red River Landing, La., was 202.7 cubic miles, of which the upper Mississippi river above St. Louis furnished 16 per cent., the Ohio 43, and the whole Missouri above Omaha, 4 per cent. The upper Missouri valley (that is, from the mouth of the Yellowstone up to the sources), and the middle Missouri valley (from the mouth of the Platte to the Yellowstone), each furnished only about 2 per cent. of the entire amount of the water which passed Red River Landing. The lower Mississippi valley, including the Arkansas, etc., furnished 32 per cent.

During March, April and May, 1882, the time of highest stage of the water of the lower Mississippi, the outflow at Red River Landing and through the Atchafalaya measured 82.7 cubic miles. During this time there flowed through the upper Mississippi river above St. Louis, 14 per cent. of the amount; through the Ohio, 38 per cent., and through the Missouri 6 per cent.; while the rivers of the lower Mississippi valley contributed 41 percent. The water that passed Omaha was 1.92 cubic miles, or 2 per cent. of the flow of the whole Mississippi during the same time. The water which flowed from the upper and middle Missouri valleys during March, April and May, 1882, was for each valley, probably only 1 per cent. of the water that flowed through the lower Mississippi river. The flood of the lower Mississippi was undoubtedly due to the great discharge of the Ohio, supplemented by heavy river inflow below the mouth of the Ohio, and the unusually heavy rainfall in the lower Mississippi valley.

The ratios of river outflow to rainfall over the catchment basins, as derived by Professor Russell from the two years' observations, 1881 and 1882, were as follows:

Upper and Middle Missouri valleys, about 335,000 square miles, 13 per cent.

Lower Missouri valley, about 210,000 square miles, 12 per cent.

Entire Missouri valley, about 545,000 square miles, nearly 13 per cent.

The upper Mississippi valley, about 172,000 square miles, 33 per cent.

Ohio valley, about 212,000 square miles, 40 per cent.

Lower Mississippi valley, about 343,000 square miles, about 27 per cent.

The above percentages, while showing the averages for two entire years, and so of decided value, are not to be depended upon for special years or months. For instance: in the Ohio valley in 1881, the outflow was 33 per cent., while in 1882 it was 50 per cent., and as the rainfall in 1882 was 180 cubic miles against 151 cubic miles in 1881, it appears evident that a much greater proportional quantity of water reaches the rivers during seasons of heavy rainfalls than when the precipitation is moderate or scanty.

Evaporation is also a very potent cause in diminishing river outflow, and as this depends largely on the temperature of the air and the velocity of the wind, any marked deviation of these meteorological elements from the normal, must exercise an important influence on the ratio of outflow to rainfall.

In connection with Professor Russell's work it is desirable to note that Professor F. E. Nipher has lately made a report on the Missouri rainfall based on observations for the ten years ending December, 1887, in which he points out as an interesting coincidence that the average annual discharge of the Missouri river closely corresponds in amount to the rainfall which falls over the State of Missouri. From Professor Nipher's figures it appears that the discharge of the Missouri river in the ten years ending 1887, was greatest in 1881 and next greatest in 1882, so that the averages deduced from Professor Russell's report of the outflow of the Missouri are too large, and should be somewhat reduced to conform to the average conditions. In different years the average of the discharge in the outflow of the Missouri varies largely, as is evidenced by the fact reported by Professor Nipher, that the discharge in 1879 was only 56 per cent. of the outflow in 1881.

In New South Wales, under the supervision of H. C. Russell, Esq., government astronomer, the question of rainfall and river discharge has also received careful attention, especially in connection with evaporation. The observations at Lake George are important, owing to the shallowness of the lake (particularly at the margin); its considerable surface area (eighty square miles), its moderate elevation (2,200 feet), and the fact that it is quite surrounded by high lands. Observations of the fluctuations of this lake have been made from 1885 to 1888, inclusive. In the latter year the evaporation was enormous, being 47.7 inches against a rainfall of 23.9 and an in-drainage of 5.3 inches, so that the total loss in depth was 18.5 inches for the year. It appears that the evaporation in different years on this lake varies as much as 50 per centum of the minimum amount. According to Russell the amount of evaporation depends largely on the state of the soil, going on much faster from a wet surface of the ground than from water; with dry ground the conditions are reversed. In 1887, the outflow from the basin of Lake George, the drainage from which is not subject to loss by long river channels, was only 3.12 per centum of the rainfall.

In the Darling river, above Bourke, says Russell, the rainfall is measured by 219 gauges. The average river discharge, deduced from observations covering seven years, is only 1.45 per centum of the rainfall, and in the wettest year known the discharge amounted only to 2.33 per centum of the rainfall, and has been as low as 0.09 per centum in a very dry year. In the Murray basin the average discharge relative to the rainfall is estimated to be about 27 per centum from a record of seven years, and has risen as high as 36 per centum in a flood year.

In connection with the regimen of rivers, it appears a proper occasion to again refute the popular opinion that the spring and summer floods of the Missouri and Mississippi valleys result from the melting of the winter snows. This is an erroneous impression which I have combatted since 1873, when my duties required a study of the floods of the entire Mississippi catchment basin. It is only within the last two years, however, that the meteorological data has been in such condition that the opinion put forth by me could be verified, namely: that the floods of the late spring and early summer owe their origin almost entirely to the heavy rains immediately before and during the flood period. Occasionally a very heavy fall of snow precedes extended general rains; but in this case the snow is lately fallen and is not the winter precipitation.

Referring to the Missouri valley, the section of the country where the winter snowfall has been thought to exercise a dominating influence in floods, it has elsewhere been shown by me that about one-third of the annual precipitation falls over that valley during the months of May and June. In either of the months named the average precipitation over the Missouri valley is greater than the entire average precipitation for the winter months of December, January and February.

Woiekoff thinks that the anomalies of temperatures shown in forest regions, particularly in Brazil--with its abnormally low temperatures, are due to heavy forests promoting evaporation, and by causing the prevalence of accompanying fogs thus prevent more intense insolation. He considers this an argument for the maintenance of forests to sustain humidity and distribute rain over adjacent cultivated land, as well as to maintain the fertility of the soil, which diminishes rapidly by washing away of the soil after deforestation.

W. Koppen has devised a formula for deriving the true daily temperature from 8 A.M., 2 P.M. and 8 P.M. observations in connection with the minimum temperature, in which the minimum has a variable weight dependent on place and month. The results of Koppen's formula tested on six stations in widely different latitudes, indicate that it is of value.

Paulsen's discussion of the warm winter winds of Greenland is interesting. These unusual storm conditions last three or four days, or even longer, the temperature being at times from 35° to 40° Fahr. above the normal, and they appear principally with winds from northeast to southeast, which Hoffmeyer believes to be _foehn_ winds. Paulsen contends that the extensive region over which these winds occur make the _foehn_ theory untenable, and that a more reasonable explanation of these winds is to be found in the course of low areas passing along the coast or over Greenland. This appears evident from the fact that not the easterly winds only but the southerly winds share this high temperature, and that as low areas approach from the west, at first the regions of the Greenland coast within its influence have south to southwest winds.

The question of wind pressures and wind velocities is a most important one in these days of great engineering problems, particularly in connection with the stability of bridges and other large structures.

Experimental determination of the constants of anemometric formulæ have recently been made both in England and this country. From results obtained in the English experiments it was concluded that the very widely used Robinson anemometer is not as satisfactory and reliable an instrument as a different form of anemometer devised by Mr. Dines. These conclusions, however, are not sustained by the American experiments, which were made by Professor C. F. Marvin, Signal Office, by means of a whirling apparatus, and under the most favorable circumstances, which yielded highly satisfactory results. Professor Marvin has lately made very careful open air comparisons of anemometers previously tested on the whirling machine, which have shown that, owing in part to the irregular and gusty character of the wind movement in the open air, taken in connection with the effects arising from the moment of inertia of the cups, and the length of the arms of the anemometer, the constants determined by whirling machine methods need slight corrections and alterations to conform to the altered conditions of exposure of the instruments in the open air. This latter problem is now being experimentally studied at the Signal Office, and final results will soon be worked out.

Professor Langley has also made very elaborate observations of pressures on plane and other surfaces inclined to the normal, which it is believed will prove important contributions to this question, but the results have not yet been published. It is important in this connection to note experiments made by Cooper on the Frith of Forth Bridge, where a surface of 24 square metres, during a high wind, experienced a maximum pressure of 132 kilogrammes per square metre, while a surface of 14 square decimeters showed, under similar conditions, 200 kilogrammes per square metre, by one instrument, and 170 by another. The opinion expressed by Cooper that in general the more surface exposed to the wind, the less the pressure per unit of surface, seems reasonable, and if verified by more elaborate experiments must have an important bearing.

There are questions in connection with which even negative results are of an important character, particularly when such results are quite definite, and tend to remove one of many unknown elements from physical problems of an intricate character. In this class may be placed atmospheric electricity, with particular reference to its value in connection with the forecast of coming weather. The Signal Office, through Professor T. C. Mendenhall, a distinguished scientist peculiarly fitted for work of this character, has been able to carry out a series of observations, which have received from him careful attention, both as to the conditions under which the observations were made and in the elaboration of methods to be followed.

Professor Mendenhall also supervised the reduction of these observations, and after careful study presented a full report of the work to the National Academy of Sciences, in whose proceedings this detailed report will appear. Professor Mendenhall says, "Taking all the facts into consideration, it seems to be proved that the electrical phenomena of the atmosphere are generally local in their character. They do not promise, therefore, to be useful in weather forecasts, although a close distribution of a large number of observers over a comparatively small area would be useful in removing any doubt which may still exist as to this question." It may be added that Professor Mendenhall's conclusions bear out the opinions expressed to the speaker, in a discussion of this question, by Professor Mascart, the distinguished physicist.

It has been generally admitted that the aqueous vapor in the atmosphere plays a most important part in bringing about the formation of storms and maintaining their energy. It has been frequently commented on by the forecast officials of the Signal Service, that storms passing over the United States were in general preceded by an increase in moisture, but unfortunately little effort had been made on the part of previous investigators to determine any quantitative relation between the actual humidity and the amount of precipitation or its relation to the storm movement. It has long been regretted that the direct relations of this to other meteorological phenomena were not more fully defined. During the past year Captain James Allen, of the Signal Office, has endeavored to apply the results of his investigations and theories to the practical forecasts of storm conditions. Captain Allen has carefully studied the relations of the potential energy of the surface air, as represented by the total quantity of heat it contained, to the movement of storm centres and the extent of accompanying rain areas. In his first investigations the potential energy per cubic foot was estimated as follows: Supposing the air to have been originally 32° and the moisture in it as water at 32°, the total quantity of heat applied to reduce to the state of observation will be A = (_t_-32)/6 + Q in which A is total heat per unit volume; _t_ is the temperature of the air, Q the total heat of vapor, and the specific heat of air at constant volume being taken as one-sixth (.168). From Regnault's formula we have Q = 1091.7 + .305(_t_-32).

For the mechanical equivalent we have J = 772A. If we divide J by the pressure estimated in pounds per square foot, it will give the height through which the pressure can be lifted if all the heat is spent in work by expanding the air.

An approximate expression for the upward velocity V may be obtained from Torrecelli's theorem from which we have V^2 = 2_gh_, _h_ in this case being the height through which the pressure would be lifted if all the heat is spent in work. The theory has been that the storm centre will move over that section of the country where V is the greatest, and that the time of occurrence and amount of rain have a relation of conformity to the changes in Q and its actual amount.

Auxiliary charts were also made showing for each station the following values of Q:

1st. Highest Q not followed by rain in 24 hours.

2d. Greatest plus change in Q not followed by rain in 24 hours.

3d. Lowest value for Q followed by rain in 12 hours.

A tentative application of the theory during December, 1889, has given very encouraging results. The problem can be approached in many different ways, but the basis of the solution is the determination of the actual energy of the air, both potential and kinetic, as well as differences of potential.

Probably the most important event of the past year to general meteorological students has been the publication of Part I, Temperature, and Part II, Moisture, of the Bibliography of Meteorology, under the supervision of the Signal Office, and edited by Mr. O. L. Fassig. The two parts cover 8,500 titles out of a total of about 60,000. This publication renders it now possible for any investigator to review the complete literature of these subjects, not only with a minimum loss of time, but with the advantage of supplementing his own work, without duplication, by the investigations of his predecessors. The publication is a lithographic reproduction of a type-written copy, the only available method, which leaves much to be desired on the grounds of appearance, space and clearness.

* * * * *

The experiments of Crova and Houdaille on Mount Venteux, elevation 1,907 metres, and at Bedoin, 309 metres, are of more than transient interest since they fix the solar constant at a height of 1,907 metres, at about three calories; agreeing with the value obtained by Langley on Mt. Whitney, Cal.

With this brief allusion to the important phenomena of sun-heat, whereon depend not only the subordinate manifestations pertaining to this section, but those relating to all other departments, this report may appropriately close.

TREASURER'S REPORT.

YEAR ENDING DECEMBER 31, 1889.

C. J. BELL, TREASURER, in account with NATIONAL GEOGRAPHIC SOCIETY.

Balance on hand as per last account . . . . . . . . . $626.70

RECEIPTS.

To amount of annual dues for 1889 . . . . . . . . . . $865
" " " " 1890 . . . . . . . . . . 20
To Life Members . . . . . . . . . . . . . . . . . . . 50
--- 935.00

Note for $1,000 with interest paid off, Nov. 16, 1869 1,032.08 Sale of Maps . . . . . . . . . . . . . . . . . . . . 1.41 Surplus from Field Meeting . . . . . . . . . . . . . 25.35 -------- $2,620.54

INVESTMENTS ON HAND, DEC. 31, 1889.

Note dated March 27, 1889, for the sum of $750, with interest @ 6%, due March 27, 1890. Secured by real estate.

DISBURSEMENTS.

By Cost of Magazine, No. 2 . . . . . . . . $174.46
" " " No. 3 . . . . . . . . 233.66
" " " No. 4 . . . . . . . . 197.28
" Directory of Society . . . . . . . . . 28.35
" Rent of Hall at Cosmos Club . . . . . . 45.00
" Printing, Stationery and Postage . . . 108.72
" Sundries . . . . . . . . . . . . . . . 13.00
1889. ------ 800.47
Mar. 26. By Loan on collateral . . . . . . . . . . 1,000.00
" Note for $750 and interest, from
March 27, 1889, for 1 year @ 6%,
due March 27, 1890 . . . . . . . . . 756.25
Balance in Bank . . . . . . . . . . . . . 63.82
---------
$2,620.54

REPORT OF AUDITING COMMITTEE.

December 27, 1889.

_To the National Geographic Society:_

The undersigned, having been appointed an auditing committee to examine the account of the Treasurer for 1889, make the following report:

We have examined the Treasurer's books and find that the receipts as therein stated are correctly reported. We have compared the disbursements with the vouchers for the same and find them to have been properly approved and correctly recorded. We have examined the bank account and compared the checks accompanying the same. We find the balance (beside the sum of $756.25 invested in real estate note) as reported by the Treasurer ($63.82) consistent with the balance as shown by the bankbook ($82.82), the difference being explained by the fact that there are two outstanding checks for the sum of $19.00 not yet presented for payment.

BAILEY WILLIS,
R. BIRNIE, JR.,
WILLARD D. JOHNSON,
_Auditing Committee_.

REPORT OF THE RECORDING SECRETARY.

The first report of the Secretaries was presented to the Society, December 28, 1888. At that time the Society had a total membership of 209. Since that date this membership has been increased by the election of 36 new members; it has been decreased by the death of 3 and by the resignation of 14. The net increase in membership is thus 19 and the present membership is 228, including 3 life members. The deceased members are, Z. L. White, G. W. Dyer and Charles A. Ashburner.