following the ancient customs of our old colonies. The foreman, with a little hammer or pincers, without regard for geometrical beauty, for which mineralogists have a sort of worship, applies himself to breaking out the stone,1 an operation which consists in reducing the mass to small pieces, in order to detach the limpid portions and to separate them not only from the rest of the veinstone, but from all that which, in the material, is not usable, and it is under this rough form of angular débris that the gems are exported to Europe for the final cutting.

The alluvial deposits are very different from deposits "en place' and less attractive. Minerals are no longer found in any sort of collective relation in their mother rock. Under the influence of the phenomena of alteration during centuries, they have been detached from their gangue little by little, drawn away from the place of their origin by the superficial trickling down, and hurried along much more quickly as they are less dense until they have been carried a long distance by torrents and mixed with other species of different nature and origin.

Under the tumultuous waters which consume the most resistant mountains, pursuing without truce a sort of eternal struggle for life, the weak minerals, the soft and fragile ones, are worn away, crushed by the strong, I should say by the hard minerals, and are eliminated in the form of fine clay; the strong resist much longer, but whatever they are, their crystals sooner or later lose the brilliancy of their faces, the keenness of their edges, and before disappearing in their turn they are reduced to the condition of round pebbles. Among them, of equal hardness, those are preserved the longest that are devoid of physical blemishes. This is a gigantic mechanical preparation, a formidable cutting, effected by natural action. It is a selection through force and beauty.

Further, the gems that subsist in beds, where they are often associated with heavy and precious minerals, such as gold, pertain to a number of more limited species; though as a rule they are less abundant, yet the proportion of beautiful stones in such cases is generally great. At Madagascar these stones are chiefly corundums, garnets,' occasionally some chrysoberyl, some spinel, and topaz.

One of the most typical of the alluvial deposits among those I visited is found to the southwest of Ambositra, in the bed of the small river Ifèmpina. Its boundary is not at all a wilderness of weeds like the Sahatany, but a forest in all its splendor, impenetrable

1 In certain works the cutting is not done in the camp (toby), but at the prospector's headquarters (Ant sirabé for example).

2 The most frequent is almandine, which shows a wide range of color from dark red to a pretty rose. Many of the cut almandines come from éluvions.

outside the beaten tracks, a forest whose glades set in great trees are peopled with many-colored birds and agile lemurs.

The few habitations along the path that led me there were no longer the small white molded clay houses of Imerina, but light wooden huts built on piles. The landscape is no more enlivened by the white "lambas" of the Hova; the natives that roam in the woods are half nude; they are the Tanalas with hairy faces.

The washing of the alluvia with the aid of primitive sluices and the "batée," still more primitive, yields, with some gold, many crystals of corundum1 much rolled. Most of them are opaque but some are transparent. By an irony of nature, that does not fail to rise again, and not without bitterness, the prospector, who kindly allowed us to visit his works-it is the uncolored corundum which forms the largest crystals could weigh them up to 500 grams.

Their limpidity is so perfect that they might well be classed as magnificent precious stones, but of a difficult setting; nevertheless the least among them would bring a fortune if it had the color of the smallest rubies and sapphires which accompanies them.

In order to find the deposits rich in rubies, and especially in sapphires, you must climb toward the north on the volcanic massif of Ankaratra, where are worked some basaltic alluvia containing débris of granitic subtraction, the original source of the crystals of corundums and zircons which accompany them."

Such are the precious stones of Madagascar, numerous, varied, and beautiful. Beryls, tourmalines, kunzite, spessartite, and uncolored corundum, in particular, could cope through their limpidity, their color, and their brilliancy with similar gems of the best known deposits of Brazil, of Ceylon, of California. Some of them, the rose beryls and the yellow tourmalines, for example, are unrivaled throughout the world. They need only to be known. As the new comes to everything, so these must conquer their right to live. I have the pleasure of presenting these to you in recognition of the pleasures that their study and their pursuit has afforded me in traversing the vast solitary places of the high plateaus illuminated by the clear sky of the southern winter, in traversing the somber vaults and dense forest.

1 The corundum crystals of this deposit are at times transformed into absolutely round pebbles, and moreover, from the situation of Ifempina and the position of the point situated up the stream where they commence to find them, they can roll on a course only a few kilometers. It is true that the valley is very winding, hollowed between cliffs of granite and gneiss; they could be used on the spot as some sort of cauldrons for giants.

By their properties and their kind of deposition these stones are identical with those of Velay (Espaly near Le Puy and Le Coupet).

The knowledge of gems constitutes only a small part of mineralogical questions which are presented in Madagascar. Its extinct volcanoes, its rocks and their minerals, its ores, their composition, their mutual relations, their genesis, their modes of alteration deserve in the highest degree the attention of men of science.

Fifteen years of work on these materials of all kinds accumulated in my laboratory of the museum through the devotion and intelligent curiosity of explorers, officers, administrators, of colonists, prospectors, had very often made me dream of the Great Isle.

This dream has become a reality. This has not in the least disappointed the hopes that had been born in my mind.

THE FLUCTUATING CLIMATE OF NORTH AMERICA.1

By ELLSWORTH Huntington.

[With 10 plates.]

PART I. THE RUINS OF THE HOHOKAM.

During his connection with the Pumpelly expedition sent out by the Carnegie Institution in 1903-4 to Transcaspia and adjacent regions the present author came to the conclusion that in the dry regions of central Asia the climate of the past was distinctly moister than that of the present. During the next two years an expedition by way of India to Chinese Turkestan, in company with Mr. R. L. Barrett, led him to extend this conclusion over a wider area and to believe that the change of climate has not progressed regularly, but by pulsations. Still another expedition to Palestine, Asia Minor, and Greece in 1909 on behalf. of Yale University seemed to confirm the pulsatory theory, and to show that the general course of history for at least 3,000 years has been in harmony with the supposed climatic pulsations. Moreover, the observations of others, even of men such as Beadnell, who do not believe that the climate of the earth has changed in recent times, seem to indicate that north Africa, on the one hand, and central Europe on the other, as well as southern Europe and large parts of Asia, have also been subject to climatic changes. Thus there seems good ground for the conclusion that during historic times essentially synchronous climatic pulsations have taken place in all of the vast region of the Temperate Zone from China on the east, across Asia and Europe, to the Atlantic on the west. Obviously, if such pronounced and widespread changes have occurred in the Eastern Hemisphere, there is a possibility that changes of a similar nature may have taken place in America. Accordingly when Dr. D. T. MacDougal, director of the Department of Botanical Research of the Carnegie Institution of Washington, invited the author to cooperate with the Desert Laboratory at Tucson, Ariz., in a climatic study of the arid southwestern portion of North America, the opportunity seemed too good to be neglected. Three seasons, consisting of three months in the spring of 1910,

1 Reprinted, by permission, abridged by the author, from The Geographical Journal, London, for September and October, 1912.

four months in 1911, and four in 1912, have now been spent in the field. The time was divided between the States of New Mexico, Arizona, and California in the United States, and Sonora, Mexico City, Oaxaca, and Yucatan in Mexico. Most of the methods of investigation were similar to those which the writer has employed in Asia, and led to a similar result. To these, however, were added some significant observations upon the relation of tropical jungle and tropical forest to civilization in Yucatan, and a series of highly conclusive measurements of trees. Both of these new and independent lines of observation confirm previous conclusions, but in the present article the facts as to Yucatan must be omitted for lack of space.

Omitting all consideration of the effect of climatic changes upon the form of the earth's surface, the composition of soil, the distribution of animals, and various other lines of thought, let us turn at once to the vestiges of pre-Columbian man found in the southwestern part of America. Some, such as the cliff dwellings and the great irrigation works and villages of the Gila Valley in southern Arizona, are famous. A far larger number, however, have received almost no attention even from archeologists. The reason is obvious. In most cases the ruins are so insignificant that an unobservant traveler might ride miles through what was once a region thickly studded with villages without being aware of the fact. Walls for defensive purposes upon the mountains or pictographs upon the face of the rocks are apt to attract attention, but few people notice the far more important sites of villages scattered in profusion over thousands of square miles, especially in southern Arizona, New Mexico, and the neighboring parts of Sonora. The sites are now reduced to barren expanses strewn with ornamented bits of pottery, flint knives and arrow heads, stone hammers and axes, mani and metate stones for grinding seeds, and in some cases rectangular lines of bowlders placed erect at intervals of a foot or two and evidently outlining the walls of ancient houses. Here and there a little mound a foot or two high shows where an ancient dwelling was located. In almost every village an oval hollow surrounded by a low wall covers an area 100 or 200 feet long by half as wide-not a reservoir, as one at first supposes, but probably a ceremonial chamber of some sort. Aside from these scanty traces nothing remains. Yet there can be no question that these were once ancient villages. Frequently the ground is full of bits of pottery to a depth of 2 feet or more, while the surface is so strewn with similar bits that one can not walk without treading on them. The houses were probably built for the most part of branches wattled with mud. Such houses disappear quickly when abandoned, for the wood decays and the clay used for wattling blows away or else is spread over the ground in such a way as not to be noticeable. The