and B Geminorum, with the outer mirrors at 13 feet separation. In February, with mirrors approximately 16 feet and 19 feet apart, observations were made on a Orionis, a Tauri, ß Geminorum and a Bootis. The seeing did not warrant drawing any definite conclusions except that fringes were seen at all points for ẞ Geminorum. This indicates that an interferometer with a base longer than 20 feet will be required to measure its diameter. Fringes were seen for a Tauri at 13 feet, at 19 feet, and in March at 14.5 feet, the visibility becoming less with increased separation of the mirrors. Additional measures will be made at points between 16 feet and 18 feet to see whether the fringes disappear as calculations indicate they should. For a Bootis the fringes were much reduced at 16 feet and could not be seen at 19 feet; the seeing was bad, however, and the observation indecisive.

Many stars have been used for checking the instrument; among them & Tauri, y Orionis, a Canis Minoris, a Geminorum, and Bootis. All have shown strong fringes at 19 feet.

η

Experience has shown throughout that better seeing is required for this work than was at first supposed, particularly when the mirrors are widely separated and the visibility of the fringes is approaching the point where they disappear. Change of seeing at these times will cause the fringes to flicker in and out, but a check is always at hand, for at the same time the visibility of the " zero" fringes is also reduced.

On some occasions in bad seeing the zero fringes will remain fixed, but the interferometer fringes will shift to the side of the image, probably because small sections of the wave front become inclined to the general wave front, due to varying atmospheric densities.

Having determined the distance at which the fringes vanish, we find the angular diameter of the object from the expression a=1.221/b where a is the angular diameter in radians (206265′′), A is the effective wave-length (in cm.) of the star or that portion of the spectrum which is most predominant in forming the fringes seen by the eye of the observer and b is the distance apart of the mirrors (in cm.); Anderson has found, in connection with his work on Capella, that the effective wave-length of a solar type star is

5.5 X 10 cm. and it is assumed for a Orionis that the value of the wave-length is 5.75 X 10-5 cm., a true value for which must be found by direct experimental work. The value of b found for a Orionis is 121 inches (± 10 per cent.). The approximate value then for the angular diameter of a Orionis is .047". The agreement of this value with those obtained by calculation, which range from .031" to .051", is striking. If there is a falling off of intensity toward the limb, as in the case of the sun, Michelson finds this value would be increased by 17 per cent. Several determinations of the parallax have been made for a Orionis and from these its distance b may be found from the expression

where R93,000,000 miles, the distance of the earth from the sun, and is the value of the parallax in seconds of arc. Measures of the parallax thus far obtained are: Adams, .013"; Yale, .032′′; Schlesinger, .016"; Yerkes, .022", the weighted mean of which is ..020". From these values the distance is about 9.6 X 1011 miles. Knowing the distance and the angular value of the star, its linear diameter is found to be 218 X 10 miles. This value is not a definite figure but only an approximation; but in any case it means that the diameter of the star is several times the distance between the earth and the sun and several hundred times the diameter of the sun itself.

The work is being continued until the half dozen stars which calculations indicate as measurable with the twenty-foot beam have been investigated. Most of these are stars having late type spectra. In order to measure diameters of early type stars such as Sirius and Procyon a much longer base is needed. For this work an interferometer with mirror separations as great as 50 or 100 feet has been discussed but it is felt the present instrument should be used to its limit and many data accumulated, particularly regarding seeing conditions with the mirrors widely separated, before anything definite is attempted in the way of a larger instrument.

MOUNT WILSON OBSERVATORY,

PASADENA, CALIF.

THE PEOPLING OF ASIA.

(PLATE VIII.)

BY ALEŠ HRDLIČKA.

(Read April 21, 1921.)

The peopling of Asia, as may well be appreciated on reflection, constitutes one of the greatest problems of anthropology. The solution of this problem could not have been approached with any great hope of success until lately, for it involves in no small degree the peopling of the whole world. Even now many of the details are lacking or obscure; but through collateral as well as direct research sufficient light, it seems, has by this time been obtained for the possibilty of our attempting, with due reservations, of some general deductions.

It is quite certain that these deductions are bound to receive substantial modifications as anthropological knowledge of the Asiatic countries and especially that of early man accumulates; they can for the present be little more than working hypotheses; nevertheless, what will be here outlined is supported by many facts of considerable weight.

Looking at the subject of the peopling of Asia with due perspective, we may readily come to the first definite conclusion, which is that the vast continent could not have been peopled either from the north or the east; and that consequently it could only have been peopled from the south, southwest or west. From this it logically follows that the eastern, central, northern and northeastern Asiatic populations must have been ethnic extensions from other parts of the continent. And as all these populations possess certain characteristics in common which enable science to classify them as mongoloid," it is further plain that they could not have come from more than one direction or from more than one ancestral land or

source.