tine records at some length his last conversation with her, in which, looking out upon the sea at the mouth of the Tiber, from the quiet shelter of a garden, they spoke of the eternal life of the saints of God, and rising in thought through all created things-the beauty of the earth and sky, the sun and moon and stars, the things that are seen and are temporal-they passed on to the contemplation of the things that are not seen and are eternal, beyond all types, symbols, shadows, imaginations, till the soul is satisfied with nothing less than the presence of Him whom it has loved, and sees Him as He is. So she fell asleep, and her son closed her eyes, and wept bitter tears. The grief of Adeodatus, as was natural at his age, was more impetuous. He burst into an agony of lamentation, and only after a time yielded to the counsels of his father and his friends, and was able to control his sorrow, and join with them in chanting the 101st Psalm: "I will sing of mercy and judgment: unto thee, O Lord, will I sing."+ own likeness so clearly, filled him with alarm. God freed him from that anxiety by quickly taking the boy into His own resting-place. There was no longer any cause to fear for the perils of boyhood, youth, manhood.* For him, doubtless, as for his own mother, Augustine poured out his soul in prayer that he might enter speedily into the joy of his Lord, remembering him at the altar of God, offering for him, as for her, (we may forgive what we may deem superstitious in this excess of natural piety,) the Eucharistic sacrifice.† So ends the episode in the life of a great man to which I have ventured to call attention. There lay before him many years of arduous work, and exciting controversies, and deep dogmatic speculation, and incessant pastoral activity. The mother and the boy fell, as in a thousand like cases, into the background of memory. They belonged to a period of his life upon the greater part of which he could not look back without horror and confusion. far as I know they are never mentioned, either of them, in any book subsequent to his Confessions. But upon the grace and beauty, and opening intellect, and growing holiness, of the son whom he had accepted from the first, however darkly, as "God's gift" to him, whose innocent infancy had won him to something like a conquest over sensu So With the death of Monica the Confessions of Augustine virtually end. The four books that follow, though nearly a third of the whole, are almost entirely destitute of biographical interest. He scrutinizes his own spiritual condition, and expatiates on the interpretation of many passages of Scripture, but the narrative of his life is not con-ality, who had gained the love of the saintly mother tinued. And hence it is, perhaps, that we have no account of the time and circumstances of the death of this much-loved son. All that we know is that it was not long after the death, which he had felt so keenly. The father can give thanks that it was so. That eager, speculating spirit, in which he saw his whom he revered-upon these we may well believe that he thought not without hope, not without thanksgiving, recognizing in them the love which had brought good out of evil, and had turned even the "fruit of his transgression" into a help towards the attainment of a true blessedness. E. H. PLUMPTRE. THE ATMOSPHERE AND THE CLOUDS. THE atmosphere, or, in more familiar terms, the "element we live in," may be described as a thin, transparent, invisible, and elastic fluid. It surrounds the earth, covering the sea and land, revolves with it, and extends to a considerable height above the summits of the highest mountains. It is fluid always, from one known extreme of temperature or pressure to another. It is ponderable, and possessed of a degree of elasticity that no compression can remove or lessen. When confined, it may be reduced into any part of its ordinary bulk, however small; and when again released, it will expand to any volume, however large. When compressed it is dense, and its elasticity, or elastic force, is in direct proportion to its density, supposing its temperature to remain unchanged. If the temperature be increased, its elastic force increases; and if it be decreased, it diminishes,-in both cases at the same rate. The atmosphere is compounded of many con Confess. ix. 23-26. + Confess. ix. 29-31. stituents, and is the most subtle and penetrating of the elements. Its laws have a direct bearing upon human life, and the products of the soil. Under ordinary conditions, it is the breath of our life; but when contaminated, it generates disease, and carries with it a mortal pestilence. The evil effects of impure air may be witnessed every day in the crowded habitations of the London poor: when joined with neglect and filth, the "element we live in " becomes a living poison. I have myself too often witnessed the evil operation of air defiled by the respiration and re-respiration of individuals, confined to a small apartment. The air so breathed is deteriorated, and deprived of the healthy properties belonging to it in nature. Inured to the morbid action of its poisonous breath, the inhabitants of a district thus defiled attest its influence in their weakly frames and pallid faces; but no outraged perceptions of taste and smell warn the sufferers of its pernicious influence, and they inhale, with blunted consciousness, an atmosphere rife with the germs of fever and premature decay. But the same atmosphere, unsullied by human neglect and sordid necessity, exists in its fullest purity for miles as we ascend, to a height greater than man has yet gone or can go. Colourless when near, its transparent depths are the medium of reflected colour, which, as we ascend beyond the influence of earthly vapours, deepens to an intensity of blue we know nothing of below. The air is a blending of subtle gases, of which more than 99 per cent. cousists of oxygen and hydrogen, a great part of the remainder of aqueous vapour and carbonic acid, with other gases in very small proportions. These quantities prevail at all elevations, whether among mountains or vertically in space, up to the greatest height which has yet been attained. With these aëriform fluids the waters of the earth mix in alterable proportions, according to the process of evaporation. Invisibly suspended, the aqueous vapour of the atmosphere varies in quantity according to the season of the year and the hour of the day: its regulating power is temperature, which, as the air becomes cooled, condenses vapour into visible form and substance. For miles above the earth a variable quantity of water is mixed with the air. It is this union of two dissimilar fluids, which produces the whole visible phenomena of cloud, haze, fog, &c. Whenever the temperature of the air declines from any cause, the moisture which at the higher temperature was in the invisible form of vapour, is condensed, and assumes the visible shape of clouds. each other, have often only the common resemblance which exists among trees, hills, or lakes, taken generally. The three principal modifications he names, and thus defines :- 1. Cirrus.--Parallel, flexuous, or diverging fibres, extensible, by increase, in any or all directions. 2. Cumulus.-Convex or conical heaps, increasing upward from a horizontal base. 3. Stratus.-A widely extended, continuous, horizontal sheet, increasing from below upward. He assumes that vapour thrown into the atmosphere by the process of evaporation, is diffusible by its own elasticity, which suffices for its ascent to any height in a perfect calm; and that clouds are the aggregation of minute drops, influenced in their method of grouping by electrical agency, the exact nature of which remains unexplained. Vapour generated from any moist body by evaporation, ascends by its less specific gravity, losing heat, both by its own expansion and by its ascending to the colder air of the upper regions and mixing with it. When in the balloon, I have seen mist or vapour, rising from marshy ground and water, dissipate in a region relatively dry; at other times vapour has risen, invisible at first, but, passing through higher regions where the relative degree of moisture has been great, indeed nearly approaching to saturation, it has assumed visible substance as cloud. Howard justly observes, that the operation of one simple principle would produce an effect at all times uniform, and varying only in degree. We should then see no density in clouds, but in their magnitude; and the same attraction that could bring minute drops of water together through a considerable space of atmosphere in a few minutes, ought not to end there, but should effect their perfect union into layers, and, finally, into rain. The clouds are specifically lighter than the atmosphere they float in, but the mode of their suspension has not yet been well determined. Gay-Lussac attributes it to upward and horizontal currents, and Howard to electrical agency. Be this as it may, different modifications or varieties of cloud exist at To discover the law of their aggregation is difficult, various elevations, and prevail according to the for the electrical conditions of a mass may be tested, season of the year, the time of day, and the amount but the operation of a variable electric force conof water absorbed into the atmosphere. In our tributing to form such mass, in the absence of declimate clouds are present nearly at all times; and monstrative proof, can only be inferred. The law a period when the sky is cloudless day and night, of attraction and repulsion by which particles, simias for eight days in May, 1848, is an exception to larly electrified, repel, or in opposite electrical states the rule of which I remember no similar instance. attract, would account for the aggregation of united Early in the present century, Howard published his particles; while accumulations fail to coalesce, and celebrated treatise upon clouds, and devised the therefore continue in a state of suspension, dependnomenclature ever since in use. This well-known ent on other influences to disperse in rain or other observer and meteorologist continued, to the latest forms of precipitation. The electrical conditions of hour of his life, to evince as much interest in me- a mass have been proved beyond the power of doubt, teorological pursuits as when he gave to the world some clouds being found charged with negative, and the valuable observations which must connect his others with positive electricity, occasionally altername for ever with the literature of cloud pheno- nating with rapidity from one extreme to another in mena. His classification includes seven divisions; a brief interval. In the nimbus, or rain-cloud, both of which three are simple modifications, the rest conditions have been found united, the depth of its compound. central mass now positively charged, whilst its fringed ragged edges exhibit the opposite extreme of a negative degree. The primary modifications, he remarks, are as distinguishable from each other as a tree from a hill, or a hill from a lake; although clouds in the same modification, considered with respect to Fog, mist, and haze may be assumed to illustrate the most elementary forms of condensed vapour, Of the seven modifications of the clouds, classified according to Howard's nomenclature, the three divisions I have named occupy respectively a distinct region of the atmosphere. To the stratus is assigned the lowest elevation, and the least development of form and structure. Its spreading vapours mix at night-fall with the creeping mists of evening, and afterwards descend in one unbroken sheet towards the surface of the earth. Its broad level plains float nearer to the ground than other modifications. It prevails in autumn when the temperature of the night is often greatly different from that of the day, and is especially the cloud of night. As the vapours rising from the heated surface of the earth during the day become condensed with lowering of temperature, so this cloud forms in the de and to contain the simple elements of more perfect cloud formations. Being separate divisions of a supplementary group, they prevail together or in turn at different elevations, when the air is moist and the temperature falls below the dew-point; that is to say, when the air becomes cooled below the temperature at which vapour is deposited upon a surrounding surface cooler than itself. Of visible vapour, they are modifications of different degrees of density. Haze is the least opaque: rising from the surface of the ground, it fades by imperceptible degrees into the ordinary transparent atmosphere. Mist is a local phenomenon, appearing chiefly in early morning or towards nightfall, and hovers like an embryo cloud for a few feet over meadows or moist surfaces, sometimes rising from the ground or creeping along the soil. Fog is the most im-clining evening, and melts away before the beams portant modification of the group: it exists at the highest elevations, is the most general, and, without question, is the most dense. It is dry or wet, and may exist in either state, in successive alternate layers, to a considerable height above the ordinary level of the clouds. The condensation of an aqueous mass consists probably in the formation of a multitude of thin vesicles of lighter specific gravity than the surrounding air. So far as I have seen, a cloud does not consist of solid drops, but of vesicles, bladderlike, after the manner of a soap-bubble, although I have never seen anything like a bladder in any cloud I have been in. That the atoms are vesicular, I rather infer from their floating, and from the optical phenomena of clouds and mists, the rainbow, halo, and corona; and from being enveloped in fog when the known amount of water present has been exceedingly small. For instance, it is generally understood that a cubic inch of water produces a cubic foot of steam. When at heights exceeding four miles, and when there was less than one 2000th part of a cubic inch of water in a cubic foot of air, a bulk of vapour or cloud has been produced sufficient to envelope us in fog. Not only did this drop of water, one 100th of an inch in diameter, in a cubic foot, make itself visible, but everything else was hidden from view. So small a solid I think must have been dispersed in a vesicular form to fill so large a space. De Saussure, whilst travelling among the Alps, found himself enveloped in a mist which was almost stagnant. He was astonished at the size of the drops, as he thought them, and at beholding them float slowly past him without falling to the ground. Some were larger than peas, and on catching them in his hand, they proved to be bladders inconceivably thin. I have, however, as I have said, never seen any bladder-like bodies in clouds. This vesicular formation, by the lighter specific gravity of its particles, would account for the suspension of clouds. But whether vesicular or minute solid drops, the measure and degree of electrical agency upon their ultimate form and structure is little else than conjecture. of the rising sun. It is of a medium degree of density, and in calm evenings ascends in spreading sheets, like an inundation, from the bottom of the valleys, or rises from the surfaces of lakes or rivers, or water generally. Its duration is frequently throughout the night. To the cumulus is given a higher elevation and more perfect development. Whether viewed from a balloon above, or from the earth beneath, it bears an important part in the scenery of the clouds. Of the densest structure it is formed in the lower regions of the atmosphere, and travels with the current nearest to the earth. Ascending from an irregular base, clouds of this modification rise into conical rounded heaps. They belong to the morning hours, and begin to form shortly after sunrise, attain their maximum in the hottest part of the day, diminish by degrees, and perfectly disperse about 'sunset. The cumulus of fine weather floats at a moderate elevation, and belongs to a region above the stratus. Clouds of this division form a natural screen to protect the earth from the direct rays of the sun in the hottest weather; and by reflexion diffuse heat throughout the atmosphere. They are greatly influenced by vicissi tudes of weather, sometimes evaporating as soon as formed or when forming, and pass quickly into other modifications. They may either continue for a period together of the same size, or rapidly increase to the bulk of mountains. Before rain they are more fleecy and of looser texture than in settled weather. Clouds of this modification have a marked character of their own, and can scarcely be mistaken for any other. Howard observes that their appearance towards sunset, when, instead of dispersing, they continue to rise, betokens the approach of thunder. He attributes the rounded and tufted figure of the cumulus to an evaporating cause beyond the mutual attraction of particles, and accounts for the rapid growth and great size of its protuberances by the attraction of large insulated conducting masses, when charged with electricity, over smaller masses within their influence. The level base from which they rise is due to the evaporation of the lower surface towards the earth during the increase of diurnal temperature. The cumulus itself, being formed of the morning vapours, carried upwards by ascending currents from the warmer earth, condenses in colder regions of the air. It does not afford rain, because drops similarly electrified repel each other, and therefore remain suspended, failing to coalesce. This is Howard's theory, based upon electrical agency. Combined with other modifications, the cumulus, in its boldest form, is the leading element of beauty in the finest regions of cloud scenery. Its numerous surfaces express solidity and depth, and give rise to multiplied reflections of light and colour. The cumulus of showery or variable weather breaks apart in fleecy tufts, white, like cotton newly carded. Looked down upon from the car of a balloon, through the medium of a clear atmosphere, they take forms, suggested by their mass, and seem to rest upon the ground. I have seen them, at a distance, like huge swans, dotted about the landscape; and at other times resembling the smoke of a simultaneous discharge of heavy ordnance. We were at the time I speak of travelling at a moderate elevation, and as we made our silent way, but little above the clouds, which were broken or detached, we could easily perceive the balloon's shadow traversing the fields and roads. Similarly we observed the shadows of cumuli clouds slowly passing over the ground. The sun at the time was shining, and the illuminated earth looked like a beautiful garden. The clouds were tinged with the blue of the atmosphere, whilst portions of the landscape were shadowed with violet. Viewed from the earth, under the action of a noonday summer sun, the cumulus is the mountaineload, culminating in the picturesque and rugged beauty which is peculiar to it. The same cloud, viewed in wet and variable weather, divides into shapeless tufts, white and flocculent, which drift across a sea of azure, and change in outline as the angle of elevation varies at which we view them, in their passage from the horizon to the zenith, and onwards to the limits of our field of view. At the highest elevation float the fibres of the cirrus, parallel, or grouped into feathery tufts, which resemble a lock or curl of hair. Their duration is uncertain; but in fine weather, with light variable breezes, the sky is seldom clear of small oblique groups of cirrus. From the car of the balloon, at a height of several miles, I have seen this cloud still many miles higher. It is the least dense of clouds. In periods of wet weather it is attracted into thin horizontal sheets, and forms at a lower elevation, subsiding into stratus. Its fibres, miles in length when parallel, converge to a point in the horizon, in obedience to the laws of perspective. In feathery whisks, curled or diverging, it is popularly known as the mares' tails. travels with the higher currents of the atmosphere, but is more often motionless. Its long extensible fibres frequently extend in parallel bars It from horizon to horizon. Howard has estimated them to be at least sixty miles in length; but at times they must be of much greater extent. In its purest form its delicately white-pencilled threads are collected into groups of oblique cirrus, or extend digressing across the sky. Floating at an elevation where the temperature is much below the freezing-point, they are believed to be formed of frozen particles, beyond the milder influences of the earth. From the great elevation of the cirrus, we may fairly assume it to be crystalline, an opinion strengthened by the fact, that it reflects, together with its derivative forms of cirro-cumulus and cirro-stratus, halos, coronæ, and other optical appearances referable to the refraction and reflection of ice-crystals, which almost invariably appear in the cirrus and its modifications. From observing the changes of the cirrus, Howard conceives them to be influenced by other laws than those which apply to the aggregation of particles of crystallised bodies, which would be uniform, and if numerous, limited. But the repeated movements and metamorphoses of the cirrus, in his estimation, betoken a large amount of electrical agency. Removed beyond the influence of the daily temperature of the earth, and presenting frozen surfaces of water, suspended at an elevation by which they reflect the departing colours of the sunset long after other forms of cloud, Howard assigns to them the action of electrical conductors, which seem to restore by degrees the equilibrium of the electric fluid; supposing the flexuous fibres of the cirrus to be interposed between the two electric states. I prefer to follow the observations of Howard, and to ground my own upon his classification, which has been accepted without dissent. Founded upon a sure basis of fact, hourly open to criticism, no one has seriously challenged the system he advances. His opinions and theories, the result of life-long unwearied activity in one peculiar field of study, are also entitled to the gravest consideration. A more extended insight into the processes of nature's great laboratory, will doubtless exhibit fallacies of conjecture which now look plausible in argument. But until that time arrives, I am well content, without committing myself to the support of theories, to rely upon his grounds of argument as trustworthy in their bearing; and to find in them the surest base that offers for further research into the phenomena of visible vapour in all its forms. Between the divisions of the group we have been considering are modifications derived from each respectively. In Howard's nomenclature they are as follows: Cirro-Cumulus :-Small, well-defined, roundish masses, in close horizontal arrangement or contact. Cirro-Stratus:-Horizontal, or slightly-inclined masses, attenuated towards a part or the whole of their circumference, bent downward, or undulated; separate, or in groups of small clouds having their character. Cumulo-stratus:-Cirro-stratus blended with the cumulus, and either appearing intermixed with heaps of the latter, or superadding a wide-spread structure to its base. Cumulo-Cirro-Stratus, or Nimbus:-The raincloud. A system of clouds from which rain is falling. The Cirro-Cumulus is formed from the fibres of the cirrus, which, passing to a lower elevation, collapse, and gather into small rounded tufts. The subsidence of the cirrus into this compound form may be progressive, or the change may be effected momentarily throughout the group. It exhibits an arrangement of small connected clouds or tufts, oftentime in layers, and floating one above another. "Mackerel sky," as popularly known, is simply the prevalence of distinct beds of cirro-cumulus. It is common in summer and fine weather. Cirro-Stratus is also a modification of the cirrus. It is formed from the subsidence of its oblique fibres into a horizontal position, at the time that they approach more nearly, grouping themselves with great compactness and regular arrangements. It is dense in the centre of the mass. Howard compares this cloud, seen in the distance, to shoals of fish, which it much resembles. Its forms are variable, sometimes presenting the appearance of bands or bars, or interwoven streaks, like the grain of polished wood. It precedes wind and rain, and shows itself in the intervals of a storm. Overhead, these clouds are seen as horizontal strata; in the distance they diminish in perspective to bands of slender filaments. Cumulo-Stratus:-This compound modification, the blending of three simple forms, is of great volume and different degrees of density. It belongs to an atmosphere surcharged with moisture, and unites without destroying the principal character of the simple form of clouds which range from one extreme of elevation to another, combining, without destroying, the leading features of the group which alternately prevail, unite, and change. Valleys open, and chasms deepen, in the obscurity of its depths. From plains of stratus the cumulus rears its Alpine crest, and towers to a level where the cirro-stratus crowns its summit, which frequently reposes on it as upon the actual mountain-top. Presently the cumulus dissolves, and merges, with its attendant vapour, into a single mighty heap. Similar volumes successively rise and form, entering from below the stratus, and unite into mountain chains, which give rise to innumerable plains and steep declivities. Looking down upon the clouds thus, they suffer no distortion from perspective. We have climbed their summit, and the view opens naturally on all sides, with a breadth we have no knowledge of of on earth. Valleys lose themselves in depths of shadow, and clouds sweep over snowy surfaces of light reflected on the plains below. Looking upward from the earth, we lose the reality of the scene, and the incumbent mass of a covered sky is crushed into a horizontal plane, upon which we see depicted the changing outline of masses foreshortened, according to the angle at which we view them. Beyond the first layer of clouds in an overcast sky, oftentimes there may be another range of dense cloud, a mile and more higher. Howard, who writes as an observer situated upon the earth, remarks of a sky covered with cirro-cumulus:-"The whole, seen as it passes off to the distant horizon, presents to the fancy mountains covered with snow, intersected with darker ridges, lakes of water, rock, and towers." Cumulo-Cirro-Stratus, or Nimbus:-I have my. self realised the truth which Howard indicates, that the increased density of single modification is insufficient to produce rain. This increased density is the union of clouds, which spread, unite, and fall into one unbroken sheet, rain falling only when the underlayer is present with another at a higher elevation. Howard observes that this upper stratum may be but a thin haze of cloud above the lower and more dense; but a compound system it must be to produce rain. Underneath the upper film or veil the denser clouds of a lower elevation arrive, merge into each other, and form a dense horizontal mass, entered from below by fresh accessions from adjacent clouds. The forma tion of the nimbus, and the system of compound layers before rain can fall, is one point of study I have had in view. It has caused me to ascend in heavy rain to test the fact I have established; but the subsidence of adjacent clouds, and the degree of proximity between the layers to produce a fall of rain, I have not yet been able to determine with certain accuracy. Twenty years ago I made experiments to deter mine, if possible, why it is that a much larger amount of rain collects in a gauge near the surface of the earth than in one placed at an elevation in the same locality. The result was shown to be that the difference of amounts collected at different elevations was intimately allied to temperature. When the rain was at the same temperature, or a little warmer than the air through which it passed, I invariably found no difference existed in the quantities of rain collected at different heights; but when the temperature of the rain was lower than the temperature of the air, a considerable difference was always found to exist. From this circumstance, it appeared probable that the difference in the quantities of rain collected at different heights is owing, at least in part, to the great condensation of the vapour in the lower atmosphere, through coming in contact with the relatively colder rain. By means of balloon ascents, I had hoped to resume those experiments, and investigate the phenomena of rain and its precipitation: why it is that sometimes it falls in large drops and at other times in minute particles; whether during rain the air is completely saturated with moisture; and, finally, to determine the accuracy of Professor Philips's deduction, that rain-drops decrease in size with elevation. In addition, I was in hopes of discovering, if possible, the space ordinarily |
