The whole central area of Europe exhibits like small quantities of rain, and the simple measure ments of quantity on the plains of the United States by no means sustain the idea that such aridity exists as to require irrigation. Yet the small number of rainy or cloudy days, and the sudden outflow of the water in streams, as well as its rapid evaporation in the somewhat caustic atmosphere that sweeps over the plains, reduce the practical value of the rain falling to little more than half the quantity when deposited elsewhere. At Niagara and Rochester, N.Y., the quantity of rain in spring is less than seven inches, and that of summer eight and a half to nine inches only. At Council Grove, Fort Riley, and Fort Atkinson, positions reach ing westward from the settled border of Kan sas, the quantity is fully equal to or exceeds that at Rochester. Even at Golden City, Fort Lyon, and Denver, great altitudes, it is nearly euqal in spring, though deficient in summer. The actual proportion of the rain falling on any district, thrown off in the ordinary. surface drainage, has been calculated with care in many cases as a basis for the construction of works for the supply of water to cities. The results are variously stated at frorn fifty to seventy-five per cent. of the annual fall, in average districts of the Atlantic States. Ellet calculated the dis charge of a stream called Anthony's Creek a tri bntary of the Greenbrier river of Virginia, by daily measurements for one year, to be seventy per cent. of the quantity falling in that year, and sixty-five per cent. of the average fall for a, period of years. In all these localities of the Eastern States a fair proportion of woodland, and also of loose soil and cultivated surface, would be included, thus affording conditions much nnore favorable to the retention of mois ture, and its absorption into the soil, than those existing on the general surface of the plains. If the rainfall of Maryland, at forty-four inches, should average to throw off sixty per cent. as a basis of available drainage for water-supply to reservoirs, there would be twenty-six and a half inches of waste, or of ordinary flow into rivers, and seventeen and one half inches permanently diverted by absorption and evaporation. And of the quantity thus retained and re-supplied to the air some portion would inevitably be re-deposited in rain; and thus the primary rainfall, its it may be called, may at the season of showers receive considerable augmentation. And this increase once established, it becomes permanent so long as the surface continues favorable, increasing the humidity of the local atmosphere and the cultivable capacity of the soil. Applying this analogy to the plains, Iv quantity of twenty inches now found falling on the dry surface, and of which seventy to ninety per cent. is immediately thrown off in the streams and rivers, may, by covering the surface with forests in part, and by breaking up the hardened turf in cultivation, diminish the waste from eighty to sixty, or even fifty per cent., retaining, say, six or eight inches of this quantity in some form, and at least pre venting the immediate waste from which no secondary benefits can now be derived. The practical value of the primary water-deposit can not fail under such change of surface to be equiv alent to an addition of ten per cent. to such original quantity; sufficient in many cases to secure important results, and to obviate deficien cies that are now decisively adverse to whole classes of crops. A further measure may be sug gested here, in the construction of what may be called temporary reservoirs, in which the surplus of the profuse showers falling in spring and early summer may he retained to be distributed by channels of irrigation, or to secure general bene fits by simple retention. The cost of such works need not be great, nor need they be more than such temporary obstruction of the smaller drain age-channels as is within the power of a few set tlers at any locality to construct at any time. For these, as for all preliminary works of the kind, the agency and means of the railroad com panies may be easily and effectively employed. Whatever may be found practicable in this respect, it is clear that eight to ten inches of rain fall in the three or four months of most rapid growth can be utilized to a much greater extent than to permit eighty per cent. of the quantity to run off at the moment it falls, affording no useful result, and only flooding the valleys of great rivers and their tributaries just at a time when no surplus is wanted in such valleys. It is a common mistake to suppose that the rain fall of England is greater than that of the United States. Recent observations in this country enable us to make the comparisons between the fall of rain in the two countries with considerable accuracy, not only as to the amount which descends annually, but, what is more important, as to the a,mount in each particular season of the year. The average rainfall of England is, in general, much less than that of the United States. In the eastern portion of England the annual fall of rain is estimated at twenty inches; in the middle portion, at twenty-two inches ; in the southern and western, at thirty ; in the extreme southwestern, at forty-five inches. In Wales it is estimated at fifty inches; in the eastern portion of Ireland, at twenty-five inches, and in the western at forty inches. The rainfall in the -United States, as shown by Blodgett's rain chart, is in the basin of the great lakes, thirty inches; on Lake Erie and Lake Champlain, thirty-two inches; in the valley of the Hudson, on the headwaters of the Ohio, through the niiddle portions of Pennsylvania and Virginia, and western part of North Carolina, thirty-six inches ; in the extreme eastern and the northern portions of Maine, northern portions of New Hampshire and Vermont, southeastern counties of Massa chusetts, central New York, northeast portion of Pennsylvania, southeast portions of New Jersey and Delaware, also on a narrow belt running down from the western portion of Maryland, through Virginia and North Carolina to the northwestern portion of South Carolina, thence up through the western portion of Vir ginia, northeast portions of Ohio, northern Indi ana and Illinois, to Prairie du Chien, forty inches; on the east coast of Maine, eastern Massachusetts, Rhode Island, and Connecticut, and middle portion of Mary-land, thence on a narrow belt to South Carolina, thence up through eastern Tennessee, central Ohio, Indiana, and Illinois, to Iowa, forty-two inches, and the same down through western Missouri and Texas to tbe Gulf of Mexico; from Concord, N. H., through Worcester, Mass., western Connecticut and the city of New York, to the Susquehanna river, also at Richmond, Va., Raleigh, N. C., Augusta, Ga., Knoxville, Tenn., Indianapolis, Ind., Springfield, Ill., St.Lou is, Mo. , thence through western Arkan sas, across Red river to the Gulf of Mobile, forty five inches; from the belt just described, the rain fall increases inland and southward until at Mobile it is sixty-three inches; the same amount also falls in tbe extreme southern portion of Florida. The rainfall of New England, it is perceived, is about double that of the eastern and middle por tions of England. Observations at London, by Dalton, for forty years gave an average fall of 20.69 inches, while observations for forty-three years at New Bedford, Mass., gave 41.03. The most striking difference as to the fall of rain in the two countries is found in the quantities which fall in single days. While we have vastly more rain in our country, we have far less rainy days. In the United States we have either decided rain, or bright, fair weather; while in England, though it seldoms rains hard, there is much of the time a fog, a mist or a drizzling rain. The records at all points of observation are unfortunately too brief to afford any proper means of determining whether the quantity of rain is greater now than it was ten years since; though great force attaches to the almost univer sal belief in such increase on the part of the more intelligent residents and observers in the interior. The range of non-periodic variation is very great in all parts of the temperate latitudes, and it is possible that our earliest practical experience on the plains WilS in a period charac terized by a succession of dry seasons. In Utah it is quite clear that practically the warmer sea sons have become far more profuse in rainfall than they were fifteen years ago; and at the east ern foot of the mountains, the settled localities, as Denver, and the districts both south and north of the original center of settlements, afford marked evidence of improvement. But there are no statistics of measurement which afford any positive evidence ; the periods observed at the military posts being quite irregular, and not sufficiently extended to establish any law of increase. On no point of practical results are both writers and observers more thoroughly agreed than in affirming the value of forests, as agents of at least local amelioration of climate.
An essential condition of the growth or improve ment of a soil by chemical decomposition of its elements and by the deposit in or on it of vege table mold, is the constant permeation of its strata by the water of rains and snows. These waters bear more or less ammonia always with them, which is the chief agent of rock decompo sition, and in practical experience the forest-soils of the Central States are found deeply decom posed and fertilized. They are also free in absorbing water, bolding it long, and yielding it slowly by subsequent evaporation and by drain age through the surface strata in permanent springs. The first result of too great aud gen eral clearings of the forests is to dry up the springs, and next to harden the surface-soil, forming a stiff mass which sheds the water of ordinary rains, and can only be permeated by water and by the roots of plants when thoroughly broken up and fertilized by artificial means. After long periods of exposure the surface becomes so bard and refractory as to bear little or no resemblance to the soft, moist, deep soil of the original woodland. The denudation of the hills and upland plains of any one of the Cen tral States will show a marked decline in produc tive capacity, from that belonging to the origi nal or first occupancy. At that time the wealth of the soil had not been wasted, nor had the gen eral exposure of the surface deprived the crops of the shelter of adjacent woods, preventing the dry and caustic winds from exhausting the vitality of every plant exposed to them. The ordinary condition of the atmosphere, as it sweeps in general progress eastward, is that of an absorbent of moisture. When rain is not actually falling the air is taking up moisture, and if nothing is offered to it by ordinary evap oration from the surface the condition soon becomes arid, or deficient in the quantity neces sary for favorable action on vegetable growths. Though a desert surface intensifies the aridity, yet an ordinary dry and denuded surface yielding no moisture by evaporation soon renders the sur face atmosphere unduly dry and caustic. The summer winds may even approach a sirocco in quality, and those of winter are piercing and destructive. The water surface of any one of the great lakes is quite sufficient to neutralize either extreme for the countries lying on the line of atmospheric circulation across those lakes; and while the actual rainfall of Buffalo, Niagara, and Lockport is but small, the air is rarely or never biting in its aridity, as when it reaches the eastern and cultivated border of the plains after traversing htmdreds of miles of sur face destitute of water, forests, or other moisture yielding conditions. The practical question is whether, with a general climate of constant rain fall, the smaller quantity of such rainfall can be diffused and distributed so as to sustain the con stant vegetation of the Central and Eastern States. What may be accomplished by replacing that which we are accustomed to regard as the natural covering of the soil in the forests? And what fur ther by cultivation, by special irrigation, and by shelter-from the present unrestricted sweep of surface winds ? In answer, it may at least be assumed that important ameliorations of the local and surface conditions are certainly within control. And the whole field of action is in a climate especially mild as compared with the north of Europe. The denuded uplands of Germany, the exposed mountain districts of Scotland, and other localities of the Eastern con tinent where cultivation struggles to reclaim every inch of surface that may be made to yield the smallest product for human support, present examples of deterioration. The entire area of the plains, and all the plateaux, mesas, and basins. of the interior nced nothing but water to make them productive in valuable staples. Every where within the United States it is warm enough, and the natural soil is rich enough. So great is this natural capacity that every observer and writer who has visited these districts believes that irrigation would be profitable in every case where it w ould be possible ; the general presump tion being that many of the valleys and river bottoms near the mountains will continue to be deficient in rain, and can only be cultivated hy the aid of irrigation. The concentration of set tlements in the basin districts of Utah and Idaho has fortunately tested this capacity for profit ahle cultivation by irrigation very thoroughly, and it is pronounced successful in all cases. The mountain streams are abundant and permanent, showing a profusion of summer as well as win ter rains on their summits. The rain vvhich would be sufficient, probably, if equally dis tributed over valleys as well as mountains, is condensed by attraction on the higher ranges, and therefore is not constant in the valleys. In short, it is not the general average supply that is so much at fault as the local distribution. But the districts on the eastern slope of the greater mountain-plateaux are probably the most difficult to deal with. The great ranges have exhausted most of the moisture of the aerial volumes from which the summer rains fall, and until their dis turbing influence has been wholly exhausted the deficiency of rain continues. Probably a belt at Denver and near the eastern foot of the mountains has the quite insufficient quantity of fifteen inches of rain annually, and another, stretching two hundred to three hundred miles eastward, has but twenty to twenty-four inches. This is not of itself decidedly adverse, and cul tivation naight here succeed without irrigation, if adequate shelter and local amelioration could be introduced, at least for the cereal crops, and many others not requiring much moisture. Saussure the celebrated Swiss meteorologist states that, in ascending the sides of a mountain into the region of the clouds, he has seen globules of water as large as small peas floating in the air, which, from their levity, were evidently hollow spheres, similar to small soap bubbles. From this observation the idea became preva lent that the water of a cloud was in a vesicular condition, or, in other words, that cloud con sists of nainute hollow spheres of liquid water, filled with air, which is rendered more buoyant by the rarefaction due to the heat of the sun; and this opinion was strengthened by the fact that clouds do not give a decomposition of the rays of light sufficient to exhibit tbe phenomena of the rainbow. In what manner such a condi, tion of water can be produced, and how it can be retained by any principle of science, has not, so far as we are informed, been explained. A soap bubble soon becomes too thin to retain its lobular form, and is resolved into the condi tion of soap water. Ordinary -water is still more unstable, and can not be retained for an instant in a hollow spherical form. We shall therefore be on the safe side if we adopt an hypothesis apparently more in accordance with known and established principles, and, if this does not furnish a logical account of all the phenomena, we must wait until further research, or light from collateral branches of science dis pels the obscurity with which this point may be involved. The suspension of the clouds can be explained by taking into account the extreme minuteness of the particles of which they are composed. In the case of mists, which are sometimes formed at the surface of the earth, and afterwards become clouds in being elevated into the atinosphere by a wind blowing between them and the earth, the particles are of such extreme tenuity as to be invisible to the naked eye, and their presence is only rendered evident by looking through a stratum of considerable thickness. The simplest method of measuring the rain, .which any one may practice for him self. is to catch the water in a cylindrical vessel, a strai2;:it-sided tin pail, and to measure the depth in inches and tenths of an inch after each shower. It hardly necessary to remark that the vessel should be so placed that it may not be screened by trees, buildings, and other obstacles from the wind which bears along the falling drops. The object of the investigation is to ascertain the number of inches of water which fall from the clouds on a given space, in a given time—for example,' a year or a season. In relation to signs foretelling rain, much has been said and written. The Signal Service of the United States now predicts storms with toler able accuracy forty-eight hours in advance. It is probable that in the near future the science of meteorology will have been so far perfected that the peculiarity of seasons may be foretold with a considerable approximation to reality. Certain phenomena in the air and peculiarities of birds hove long been known to indicate a change in the W-eather. Many years ago the learned Dr. Jenner embodied these in verse, in reply to an invitation front a friend with whom he had planned an excursion the following day. It embodies about all that is known to-day upon that branch of the subject, and w-e reproduce it as being reasonably correct: