cient organization of health boards, health inspectors, etc., and a more thorough discharge of their respective functions. The civil police, by perfect discipline and efficient organization, have succeeded in nearly banishing the crimes of theft, robbery and arson outside of Wall street and the American Congress. If life and health were of as much consequence, in the general estimation, as money, or the miserable spoils of office, it would be an easy matter to organize and equip an army of health police, clothed with powers as arbitrary to abate wrongs against the physical well being of the individual and the community, as have the civil police in arresting the lesser evils of street vagrants, drunkenness, private trespass, petty thieving, or highway robbery. The slow progress of civilized society in this direction has been due mainly to the uncertain latitude, in the mind of the devout and superstitious, of the line which separates man's responsibility from that of Providence. It is the natural tendency of such minds to refer all surprising and apparently occult phenomena to a divine agency, or to the infernal pranks of a demoniacal spirit. Unhappily, morbific phenomena, when extraordinary, have usually been classed in one or the other of those categories. Thus arose the custom of blindly referring to Providence, or to an evil genius, the visitations of disease and pestilence when their courses were marked by any considerable degree of virulence and fatality. Such senseless sentimentality must come to a speedy and an inglorious end. The reputation of Providence no less than science demands that all phenomena be put to the test of independent research and observation; and that all possible diligence be exercised by society no less than the individual, in abating all evils of whatever nature that offend against the welfare of the individual and afflict the social state.

ART II.-1. Occasional Papers; or, The Theory of Glaciers. By J. D. FORBES.

2. Études sur les Glaciers. By L. AGASSIZ. 1840.

3. The Forms of Water in Clouds and Rivers, Ice and Glaciers. By JOHN TYNDALL, LL.D., F.R.S. London. 1872.

ACCORDING to the conclusions of geologists a few years ago, the primeval oceans of our globe were maintained by the radiation of heat from the internal fires of the earth, at a much higher temperature that at present. The greater dissolving powers of warm water, and the constant mechanical action of the water, kept in motion by the same causes which still move the ocean, would rapidly wear away the solid parts of the earth's crust, and transport the débris to other places. Now, whether the waters of the ocean were ever at a much higher temperature than at this time, or not, we know from observation that they are constantly producing changes in the external configuration of the earth; and we hence conclude that the same process has gone on in all ages of the world, ever since the ocean had an individual existence. Rivers have been no less potent in their influence in proportion to their extent; and even rains and snows have added their mite to the great changes which the earth's crust has undergone in past and present periods of terrestrial existence.

The slow revolutions which have been brought about on the surface of the globe, by the indirect influence of rain and snow, and especially the latter, are wonderful beyond our first conception. The melting of the snows which accumulate on the tops of the declivities of mountains, in the cold season of the year, below the line of perpetual congelation, and the rains which fall during the warm portion of the year, give rise to streams which wear away the hard material in their course, and carry to the valleys and the low lands large pieces of rock, which have been loosened by frosts and brought to a lower level by the force of gravity, and in this way they contribute to the change which is constantly taking place. Some

times the sudden melting of large bodies of mountain snows produce floods which, in modern times, destroy much property, and otherwise affect the general conformation of the earth's surface to a considerable extent. But it is not of the rains which annually fall, nor of the snows which annually fall and melt, that we intend to speak at this time; but rather of those vast accumulations of snow which find a resting place on the parts of mountains which lie above the line of perennial frosts, or which at some former epoch did rest there, and which were the sources of glaciers of greater or less extent.

The height of the snow line, or the line of perpetual congelation, above the level of the sea, varies with the distance from the equator. In Equatorial America it rises to an elevation of 15,000 or 16,000 feet; but in the Swiss Alps the snow line descends as low as 8,500 feet, while the higher peaks of the Alpine chain attain an altitude of 12,000 to 15,000 feet above the level of the ocean. In those higher regions of the earth's surface, the snow accumulates from year to year, and if there were no counteracting causes, the frozen mass would add almost indefinitely to the altitude of Alpine summits. The great weight of these masses of snow presses out the air which the snow contains, from the lower portions, and this, with the aid of partial thawing and then freezing, gradually converts the mass into ice. The force of gravity slowly brings the whole down into the valleys between the peaks, thus producing glaciers or rivers of ice. Since the snow falls periodically, the accumulated mass becomes stratified. This stratification extends to the upper part of the glacier, which is here composed of a coarse granular snow called néré by the French. The lowest part of the glacier is composed of solid ice. These glaciers are not limited to the regions which lie above the line of perpetual snow, but they extend far down below that line, into a warmer climate, even so as to encroach on fields of grain.

The appearance presented by glaciers is full of picturesque beauty, and even sublimity. Where the ice-stream descends a steep slope or precipice, an icy cascade is formed, the ice being broken by the immense strain to which it is subject, and

it thus assumes beautiful forms, with peaks and pinnacles which project above the general level. "If it were possible," says Mr. Higgins, "to imagine the ocean ruffled by a gentle breeze, and consolidated, or a boundless mirror of ice, the reader might have some idea of the forms in which a glacier may be presented to the eye of the traveller; but nothing less than a view can give him a conception of the terrific scene, or the amazement, if not the terror, with which the appearance is first beheld. The traveller, as he passes over the mighty frozen ocean, may well imagine that he feels the billows swelling beneath his feet; he stands in a new world, surrounded by new scenes; no living object is there, and no sound except his own feeble voice, and the detonations of the ice as it tumbles in fragments down the yawning precipice; not a flower or a tree can be seen, except the lowly pine, which seems to be left as though to mourn over the grave of nature." This description applies when the day is cold, and the feeble influence of the sun's rays is unable to loosen the little streams from their icy fetters. During a day of mild rain, however, or of hot sunshine, innumerable little streams of clear water flow in icy channels on the surface of the glaciers, but at the going-down of the sun these gradually freeze up, so that at night all is hushed and silent.

The little streams which flow in the daytime are often precipitated into deep fissures in the ice, and thus, with springs, contribute to the formation of torrents, which flow in tunnels at the bottom of the glaciers, for miles, and finally issue at their extremities from beneath beautiful caverns or arches. Thus, some rivers, like the Rhone, have their source in glaciers. Such is a general description of glaciers, as they appear to the eye of the traveller.

The Swiss glaciers have been more thoroughly studied than any others which are known. The amount of surface on the Alps covered with ice is more than fifteen hundred square miles, and its thickness varies from eighty to six hundred

* These fissures are sometimes twenty, thirty, and even a hundred feet in width.

feet. There are thirty-four glaciers which border the snowy region of Mont Blanc, and ninety-five square miles of snow and ice cover that mountain.* The crests and higher parts of the Alps, which are often vast table lands, or plateaux, containing from one hundred to three hundred square miles, are covered with continued masses of ice of considerable thickness, and through this the lofty peaks rear their summits to considerable elevations above. These plateaux are called seas of ice (mers de glace), which form the higher parts of the glaciers. The length of the Swiss glaciers is sometimes between twenty and thirty miles; and their width in the middle portion occasionally two or three, with a thickness of six hundred feet.+

At the extremity of a glacier there is usually a heap or mound of rocky fragment, of sizes varying from fine material to large pieces, and such an accumulation is called a terminal moraine. Along the margins of the glaciers, and sometimes in the middle portion, there are ridges, or continuous heaps, of similar material; and these are called lateral and medial moraines. These moraines are formed by the wearing away and the breaking off of the rocks which lie along the edges of the ice-streams. The medial moraines are produced by icestreams joining together, as one stream of water flows into another, and thus becomes a branch. The marginal moraines of the main stream and its branch join together, and thus form a moraine in the middle portion of the consolidated glacier.‡ We may hence conclude that any glacier which has one or more medial moraines, has one or more branches. The motion of the glaciers (of which more hereafter) causes the existence of continuous ridges, or lateral and medial moraines.

Since these moraines-and especially the terminal moraines which are the accumulation, as a general thing, of all the others are not deposited in running water, the material of which they are composed is not sorted according to size and specific gravity, as is the case where the water is in motion, and hence there is no stratification in their structure.

Somerville's Phys. Geog., p. 53. Lycell's Prin. Geol, vol. i., p. 365. Tyndall's Forms of Water, p. 55. The medial moraines were first explained by M. Agassiz.-Etudes sur les Glaciers.