back to the United States. The living collection is now on exhibition at the New York Botanical Garden.

Bahia, Brazil, was the first place visited, which city served as a base for collecting trips into the interior of the State of Bahia. One of these was to the town of Joazeiro, located about 300 miles north-northwest of Bahia, and lying in a typical cactus desert, although this region is traversed by the large Rio Sao Francisco. Notwithstanding the fact that this stream is full the entire year, little or no attempt is being made to use the water for irrigation purposes. The country is of that type known as "catinga," and resembles in a remarkable way the deserts of the West Indies; indeed, the genera of plants are in many cases the same, though the species are distinct. Here was seen the "carnuba," or wax palm, from which is obtained the wax utilized in making records for phonographs. Near Joazeiro is the Horto Florestal, or "forest garden," a Government experiment station in charge of Dr. Leo Zehntner, who rendered great assistance in the study and collection of the cactuses of the region.

- After making short stops at various stations in returning to Bahia, a trip was made to Machado Portella, a small town about 175 miles west and a little south of Bahia, the terminus of a little narrow-gauge railway. This is also a semiarid region and proved exceedingly interesting botanically. The next side trip was to Toca da Onca, still farther south, on the edge of a thick tropical forest and in a region much more humid than the northern part of the State.

About six weeks were then spent in beautiful Rio de Janeiro and vicinity. Here, even in the city itself, a botanist finds a great deal to interest him, for the trees are covered with epiphytic cactuses, mostly of the genus Rhipsalis, and within the city itself rises the picturesque Corcovado, a thickly wooded mountain on whose slopes are found many rare ferns and tree-inhabiting cactuses. The Jardin Botanico in this city is one of the finest in the world. Over 200 species of palms from all parts of the tropics are here grown in the open, besides many other rare tropical plants. In another section of the city, in a fine large park called the Quinta Boa Vista, is the Museo Nacional, where a number of rare cactuses were found in the herbarium.

From Rio de Janeiro an ascent of Itatiaya, the highest mountain in Brazil, was made, and on the very top, 10,000 feet above the sea, was found a small cactus with beautiful rose-colored flowers. Excursions were also made to Cabo Frio, to Ilha Grande, and to the islands in the Bay of Rio de Janeiro. A few days were spent in the Organ Mountains, near Petropolis, the summer home of the wealthiest classes of Rio de Janeiro. This range of mountains merits a more thorough biological exploration than has been hitherto undertaken.

Proceeding southward, a day was spent at Santos, Brazil, the world's greatest coffee center. Buenos Aires was visited next, although but little time was spent in the city. Several visits were made to the fine suburb of La Plata, where resides Dr. Carlos Spegazzini, the leading authority on Argentine cactuses.

From Buenos Aires a trip was taken across Argentina to Mendoza, a city situated near the foot of the Andes, in a region favorable to the growth of succulent plants. From there a short excursion was made to Portrerillos, Argentina, on the railway which leads to Valparaiso, Chile. Many very interesting plants were found in both these places.

In the city of Cordova, Argentina, northwest of Buenos Aires, the cactus collection of Dr. Frederick Kurtz was found to contain some rare types, which were very kindly submitted for examination and study. In this vicinity, as well as in the neighboring town of Cosquin, many cactuses were collected on the semiarid peneplain.

FOG-CLEARING INVESTIGATIONS.

Aided by a grant of $2,000 from the Smithsonian Institution and a grant from the Research Corporation, a committee of electrical engineering experts, under the general direction of Mr. F. G. Cottrell, continued during 1915 the investigations begun at San Francisco by the University of California, in cooperation with the United States Lighthouse Service, relative to the clearing of fog by means of electrical precipitation. In a preliminary report read at the first meeting of the committee, Prof. Ryan, of Stanford University, says:

Science has established the fact that all dust and fog particles in the open atmosphere are electrified and subject to dispersion or precipitation. It is apparent, therefore, that a source of very high direct voltage, with facilities for control and application, may be of inestimable value in certain quarters and seasons for clearing fog away from a street, from along a passenger railway, from around the landing stages of a ferry, or, possibly, about or in advance of a ship under headway at sea.

The clearing of fog differs from the treatment of smoke and fumes in several respects, principally in that the smoke particles must be actually deposited on the electrodes to bring about the desired effect, whereas in treating fog it is only necessary to cause coalescence of the minute particles into larger ones to give much greater transparency, even disregarding the more rapid settling of the larger drops. However, other difficulties are to be expected in the problem of clearing fog, such as the conditions arising from the continual immersion in the wet atmosphere. What is chiefly needed for an intelligent conception of the problem is actual first-hand experience in handling these and other unusual conditions.

The most striking features of the apparatus used in these experiments are the Thordarson 350,000 to 1,000,000 volt transformers, which I saw while visiting the San Francisco Exposition.

A great deal was learned during the year about the electrical technique of the problem, and although days of suitable fog conditions were extremely scarce, on the rare occasions of actual trial very perceptible clearing for a short distance around the high-tension wires was obtained as the fog swept past.

EXPLORATIONS OF ANCIENT MAYA CITIES IN GUATEMALA AND HONDURAS.

Through the courtesy of the Carnegie Institution of Washington, the Smithsonian Institution has been enabled to participate in some very interesting explorations in Central America. Prof. W. H. Holmes, head curator of anthropology in the National Museum, gives the following general account of his work in that country:

In February, 1916, owing to a generous grant of funds by the Smithsonian Institution, the writer had the good fortune to become a member of the Car

negie Institution's archeological expedition to Central America under the able direction of Sylvanus G. Morley. The work of exploring and studying in detail the remarkable remains of the ancient Mayan culture was vigorously carried forward. An especial object of the expedition was the discovery of additional inscriptions embodying glyphic dates, for it is the dates, now read with facility, which furnish the skeleton of Maya history.

Among the ancient cities visited while the writer was associated with the expedition were Antigua, the ancient Spanish capital of the kingdom of Guatemala, built on the site of a prehistoric city; the extensive ruins of the ancient city of Iximache, near the site occupied to-day by the capital of Guatemala, Guatemala City; the ruined city of Quirigua in eastern Guatemala, the subject of much scientific interest during recent years; and the ruins of Copan, in Honduras, perhaps the most remarkable of all the American monuments of antiquity.

Especial attention was given by the writer to the collection of data and drawings to be utilized in preparing panoramic views of the several cities visited, and every effort was made to obtain information regarding the technical methods employed by the ancient builders. The quarries from which the stone was obtained were too deeply buried in tropical vegetation to yield up their story without extensive excavation and the methods employed in dressing and carving the stone remain in large part undetermined. Certain chipped and ground stone implements that could have served in dressing the stones used in building were found in numbers, but the story of the carving, especially of the very deep carving of the monuments of Copan, remains unrevealed. Although it is thought that stone tools may have been equal to the great task, it is believed by some that without bronze the work could not have been done. There are, however, no traces of the use of bronze by the Central Americans.

The monuments are on a grand scale and great skill and excellent taste are manifest in their embellishment, the whole giving evidence of a state of culture advancement unsurpassed in any other part of aboriginal America.

STUDY OF NOCTURNAL RADIATION.

Several grants from the Hodgkins fund have been made to Prof. Anders Ångström during the past few years to enable him to carry on researches on the radiation of the atmosphere, particularly nocturnal radiation. The results of observations made by him in Algeria in 1912 and in California in 1913 were embodied in a pamphlet published by the Institution in 1915. In this pamphlet he summarizes his work as follows:

The main results and conclusions that will be found in this paper are the following. They relate to the radiation emitted by the atmosphere to a radiating surface at a lower altitude, and to the loss of heat of a surface by radiation toward space and toward the atmosphere at higher altitudes.

I. The variations of the total temperature radiation of the atmosphere are at low altitudes (less than 4,500 m.) principally caused by variations in temperature and humidity.

II. The total radiation received from the atmosphere is very nearly proportional to the fourth power of the temperature at the place of observation.

III. The radiation is dependent on the humidity in such a way that an increase in the water-vapor content of the atmosphere will increase its radiation. The dependence of the radiation on the water content has been expressed by an exponential law.

The fractional

IV. An increase in the water-vapor pressure will cause a decrease in the effective radiation from the earth to every point of the sky. decrease is much larger for large zenith angles than for small ones. V. The total radiation which would be received from a perfectly dry atmos

phere would be about 0.28; observation.

cal. cm.2min.

with a temperature of 20° C. at the place of

VI. The radiation of the upper, dry atmosphere would be about 50 per cent of that of a black body at the temperature of the place of observation.

VII. There is no evidence of maxima or minima of atmospheric radiation during the night that can not be explained by the influence of temperature and humidity conditions.

VIII. There are indications that the radiation during the daytime is subject to the same laws that hold for the radiation during the nighttime.

IX. An increase in altitude causes a decrease or an increase in the value of the effective radiation of a blackened body toward the sky, dependent upon the value of the temperature gradient and of the humidity gradient of the atmosphere. At about 3,000 meters altitude of the radiating body the effective radiation generally has a maximum. An increase of the humidity or a decrease of the temperature gradient of the atmosphere tends to shift this maximum to higher altitudes.

X. The effect of clouds is very variable. Low and dense cloud banks cut down the outgoing effective radiation of a blackened surface to about 0.015 calorie per cm.2 per minute; in the case of high and thin clouds the radiation is reduced by only 10 to 20 per cent.

XI. The effect of haze upon the effective radiation to the sky is almost inappreciable when no clouds or real fog are formed. Observations in Algeria in 1912 and in California in 1913 show that the great atmospheric disturbance caused by the eruption of Mount Katmai in Alaska, in the former year, can only have reduced the nocturnal radiation by less than 3.0 per cent.

XII. Conclusions are drawn in regard to the radiation from large water surfaces, and the probability is indicated that this radiation is almost constant at different temperatures, and consequently in different latitudes also.

Another grant was made to Prof. Angström in October, 1915, for a study of nocturnal radiation in the far north during the long Arctic night. Concerning this study he wrote to the Institution on February 16, 1916, as follows:

Through this grant I have been able to make observations on nocturnal radiation during the Arctic night in the north of Sweden, at a place named Abisko, at about 68° 30′ latitude. The observations were extended during about a month (Jan. 1-26) and were obtained under various atmospheric conditions. One night observations were taken at a temperature of -30° C. (-20° F.), when consequently the absolute humidity must have been very low. In general, these observations confirm the views expressed in my paper in regard to the influence of temperature and humidity upon the nocturnal radiation and the radiation of the atmosphere.

1

In connection with the named measurements observations were also made on the cooling of snow surfaces under the temperature of the surrounding air as a consequence of nocturnal radiation. As was to be expected, a linear relation was found to exist between the radiation and the named temperature difference.

1 Smithsonian Misc. Coll., Vol. 65, No. 3, 1915.

I hope in the near future to get an opportunity to extend these important observations on the connection existing between radiation and the cooling of various materials existing on the earth's surface. The question is one of scientific as well as of practical agricultural interest.

HARRIMAN TRUST FUND.

Dr. C. Hart Merriam, research associate of the Institution, aided by the income of a trust fund established for the purpose by Mrs. E. H. Harriman, has continued his zoological investigations, particularly the study of the big bears of North America.

RESEARCH CORPORATION.

The Research Corporation was established in 1912 under the New York State laws with the Secretary of the Smithsonian Institution as one of the directors and a member of the executive committee. The primary object of the organization was to develop certain patents described in previous reports which had been offered to the Institution by Dr. F. G. Cottrell but which could not be administered directly by the Institution. Other inventions and patents have since been acquired by the corporation, and through royalties from the installation and utilization of these patents a considerable fund has been created and the income therefrom will be devoted to the advancement of technical and scientific investigation and experimentation through the agency of the Smithsonian Institution and such other scientific and educational institutions and societies as may be selected by the directors.

The Cottrell patents relate to the precipitation of dust, smoke, and chemical fumes by the use of electrical currents. Successful commercial installations have already been made on the following fumes:

(a) Silver fumes from electrolytic slimes of copper refinery; (b) tin fumes from detinning process residues; (c) hydrochloric acid fumes from cleaning vats in electrogalvanizing plant; (d) tin and zinc fumes from waste metal recovery plant; (e) "low-bleach" from electrolytic plant; (f) sulphuric acid mist from contact acid plant; (g) lead fumes from copper converters; (h) fumes from roasting of zinc ores; and (i) dust from buffing wheels and from machines for powdering slate.

NATIONAL RESEARCH COUNCIL.

At its annual meeting in Washington in April, 1916, the National Academy of Sciences voted unanimously to offer its services to the President of the United States in the interest of national preparedness, and it was suggested that the academy "might advantageously