The collection as displayed in a wall case at the west end of the hall is selected to show kinds and geographic distribution. Inasmuch as this water itself presents to the eye no marks of differentiation the samples are displayed in the original package. The collection is accompanied by a map showing distribution in the United States.

THE GEOLOGY AND MINING INDUSTRY OF LEADVILLE, COLORADO.

A wall case at the north end of the east range on the first floor has been devoted to this collection, of which the following is a transcript of the label:

The prevailing and most important ore of Leadville is an argentiferous galena, which below the zone of oxidation is associated with zinc blende and pyrite. The secondary silver-bearing minerals are argentiferous cerussite, or carbonate of lead; cerargyrite, or chloride of silver; the chlorobromide of silver; less frequently chloroiodide of silver; and very rarely native silver. Lead also occurs in secondary forms, as anglesite, or sulphate of lead; pyromorphite or chlorophosphate; occasionally as litharge, and rarely as minium. Zinc occurs in the form of calamine, or silicate, while iron occurs as magnetite, hematite, or limonite, oxidation products of pyrite. Gold occurs in the native state in the form of small leaflets. More rarely occur ores of manganese, arsenic, antimony, molybdenum, copper, bismuth, and vanadium. By far the most important of the ores occur in the blue-gray dolomitic limestone of the Lower Carboniferous formation and associated with intrusive bodies of porphyry, either overlying or cutting across it, and which are known as white, or Leadville porphyry, and gray porphyry. The gangue of the ores is mainly some form of silica (mechanically or chemically combined with hydrous oxides of iron and manganese) and a great variety of hydrous silicates of alumina and barite. The main mass of argentiferous galena or lead ore is found in calcomagnesian beds. The ores containing gold and copper are more frequently found in siliceous beds, in porphyries, or in crystalline rocks.

The ores are assumed to have been deposited from aqueous solution and originally in the form of sulphides. They are of later origin than the inclosing rock, and were deposited not later than the Cretaceous period. It is believed that the metallic contents of the ores were derived mainly from the neighboring and overlying eruptive rocks.

The exhibition comprises all the principal types of rocks and ores, together with a relief map of sections of the region, as collected and produced by the U. S. Geological Survey.

CENSUS OF THE COLLECTIONS, DEPARTMENT OF GEOLOGY.

The exact number of individual specimens in the department can not be given as may readily be understood on a moment's consideration. A rock fragment to-day considered one specimen may to-morrow be broken into a dozen pieces, and a single handful of small fossils may comprise a hundred or thousand individuals. In the exhibition series it is the custom to consider as one specimen the material covered by a single label, though it may weigh from a grain to a ton or more, whether it be a single fossil of pinhead size, or an aggregate

of several thousand. These facts have been taken into consideration and allowances made accordingly in the following table. Owing to the large number of individual specimens considered essential to the proper representation of a single species, the collection of invertebrate fossils is alone numerically as large as all the others of the department combined. As already stated the collections are separated into two series, one placed on public view-the exhibition series-and one stored away in drawers and available only to students and specialists, and known as the study series.

These figures represent the number of individual specimens and fragments. number of individual falls and finds represented is approximately 500.

1,354, 392

1,407,575

The total

SOME OBSERVATIONS ON THE NATURAL HISTORY OF

COSTA RICA.

By ROBERT RIDGWAY.

[With 5 plates.]

One beautiful morning in May, 1867, after a voyage across the placid Caribbean Sea, beneath a sky equally blue and serene, the passengers on board the Pacific Mail side-wheel steamer Henry Chauncy came out on deck to view the scene on shore. We had docked at the port of Aspinwall (now Colón), the Caribbean terminus of the Panama Railway. Many of the group had never before seen the glorious vegetation of the Tropics, and to them the view was startling in its novelty and beauty. To the writer, the effect was such that it had ever since been his desire to see again, but under conditions favorable to a more intimate acquaintance, the virgin forest of the so-called Torrid Zone.

The opportunity so much desired and so eagerly anticipated did not occur until nearly two score years later, when, on the morning of December 8, 1904, after another voyage across the calm expanse of the Caribbean, the densely wooded mountains of Costa Rica loomed high among the clouds, a majestic background to the varied scene. Our steamer had arrived during the night at Puerto Limón, the Caribbean seaport of Costa Rica; a neat little city, whence are shipped to northern markets the coffee and bananas which are the chief exports of the little Republic. Far beyond the town, but seemingly only a few miles distant, the scarred and calcined summit of the Volcan de Turrialba constituted a conspicuous landmark, every detail sharp and distinct through the transparent atmosphere. On either hand stretched the coast line; to the right, snowy breakers dashing over coral reefs, the exquisitely wooded little island of La Uvita, just offshore, resting like an emerald on the sapphire waters of the bay; to the left a wall of giant grasses, except where the tall plumes of coconut palms fringed the higher portions of the shore line.

The train for San José, the capital, nestling two-thirds of a mile above the sea among the mountains of the interior, leaves for its des

tination in the morning. At first the railway skirts the coast, the blue expanse of the Caribbean close by on the right; on the left a solid wall of primeval forest, except where this is broken by an occasional small clearing. Soon the track turns inland, alternately passing through swampy forests of palms and other tropical vegetation of bewildering splendor, and, on ground less wet, extensive plantations of bananas, where are produced most of that fruit which is consumed in the United States. Ere long the ground, still densely wooded, becomes less flat; the verge of the coastal plain has been reached, and the train meanders among the foothills, which become higher and higher until the engine puffs strenuously in its effort to overcome the increasing grade. The aspect of the forest gradually changes; palms are less in evidence, a solid mantle of closely matted "broad-leaved" trees, in appearance essentially like those of our northern woods but with foliage of a darker, more somber green and with broader and more dome-shaped or flattened crowns, forming the mass of the all-embracing forest. The air becomes sensibly cooler until, toward the summit of the line, the temperature is as bracing as that of a fine October day in the States. The scenery from the car windows is constantly changing, for every turn of the road-and the curves are very frequent-brings into view a picture more magnificent, if possible, than those left behind. Far below, on the left, through a deep and densely wooded gorge, rushes the Rio Reventazón, the mountain wall beyond backed by range over range of mountains until the most distant blend with the blue of the sky. In proceeding upward the first considerable break in the continuity of forest is where the Indian village of Tucurríqui is seen across the canyon of the Reventazón, perched high above the foaming stream on a comparatively level bench, surrounded by extensive areas of open pasture and cultivated fields of sugar cane, maize, and upland rice. Gradually such open spaces become more frequent and of greater extent until near Cartago, the former capital, on the southern slope of the Volcan de Irazú, little woodland can be seen. Here, 4,500 feet above the sea, the bracing, almost chilly, air and stone fences around the fields are strongly suggestive of New England; a very transient illusion, however, for many of the telegraph and telephone poles are observed to bear not only foliage of their own but also orchids, ferns and other epiphytic plants; the nightblooming cereus and other cacti grow upon the stone walls, and the low red-tiled houses of the inhabitants are of a style of architecture never seen in northern countries. The highest point along the railway is reached at El Alto, a few miles beyond Cartago, at an elevation of exactly 1 mile above sea level. Thence the road descends to San José, the capital, near the head of a broad valley between the Cordillera Centrál, just crossed, and the Cerro de la Candelária,

at an elevation of 3,500 feet. From San José are plainly visible the volcanoes of Irazú, Barba, and Poás, of the central range; in the opposite direction the Candelaria Mountains are seen so clearly that the fields of sugar cane, maize, and rice which cover their slopes can easily be recognized by the hue of green peculiar to each, while close to the summit of the highest peak the gigantic evergreen oaks are clearly silhouetted against the sky.

From San José to the Pacific Ocean extends a region greatly different in appearance and climate from that of the eastern or Caribbean slope. The latter is a region of perennial rains; indeed, the rainfall is excessive during a considerable portion of the year, and even during the drier months there are daily showers, mostly "sun showers" of short duration, though often several occur each day, the higher portions of the mountains being perpetually saturated with rain or dense, wet fogs.1 On the Pacific slope, however, the year is sharply divided into two very different seasons, a wet and a dry, each of six months duration. The inhabitants speak of the former as their winter (el invierno), the latter as their summer (el verano). The dry season is practically rainless and cloudless; many trees shed their foliage as completely as do those of northern countries in winter;2 pastures become poor, and toward the end of the season conditions of severe drought often prevail. On the other hand, the forests, pastures, and plantations of the Caribbean slope are perpetually green; the trees shed their leaves, to be sure, but, except relatively very few species, they are dropped one by one or a few at a time and are at once replaced by new ones.

Two visits were made to Costa Rica, one covering about six and the other three months, during which the country was traversed from ocean to ocean and from sea level to the summit of several of the highest mountains. A study of the bird life was the main purpose of the explorations, and a large and valuable collection was made for the United States National Museum. In this work every possible assistance was rendered by the Government of Costa Rica, which generously detailed the taxidermist of the Museo Nacionál to accompany the writer during his different excursions, besides extending other courtesies; and also by my friends Señor Don José C. Zeledón, and Señor Don Anastasio Alfaro, director of the Museo

1 The average annual rainfall of the Caribbean slope is said to be from 230 to 300 inches, and at one station, Sarapiquí, on the northern slope, 112 inches were recorded during the month of December alone, while at Puerto Limón there was a rainfall of 41 inches in three days.

2 In some parts of the Pacific slope, as, for example, in the forests of the Rio Grande de Tarcoles, I estimated that between one-third and one-half of the trees were leafless.