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The simple instrument with which the measurements presented in this paper were made has been described in several papers by Weyde and Frankenburger ([see 1 of “References” at end of paper] and others elsewhere. It may be just stated that it consists mainly of a test-tube with a liquid coloring red under the influence of that part of the ultra-violet spectrum which produces the erythema and which is therefore of particular biological importance. The color of the liquid is compared with a standardized color-wedge that gives units of radiation which are calibrated against erythema-doses. The instrument is not only cheap but also easy to handle and to carry. There exist as yet only a few series of observations, the most important of which have been conducted by Knepple [2] and Ungenheuer [3] at Oberstdorf, Bavaria, Germany, in the high mountains, by Bossolasco [4] during the International Polar Year at Mogadiscio, Italian Somaliland, Africa, and by Fuchs [5] on an expedition through south-central Europe.

The sound-phenomena accompanying earthquakes are not yet fully explained as regards their origin. In particular, the question whether they are produced by the felt, or recorded, shock-waves themselves, or are to be regarded as independent waves, has not been satisfactorily answered. The shock-waves recorded at Mt. Tukuba lead W. Innouye [see 1 of references at end of paper] to believe that they might induce sounds. There, with short periodic accelerographs, wave-periods of 0.02 second have been observed, well within sound-frequency. On the other hand, from mapping sound-intensities in epicentral regions, A. Sieberg [2] found that sound-centers were often different from the shock-foci.

Biological as well as geological research has made very successful use of the qualities that the physicists have detected in radioactive substances. Outstanding examples for the vast new fields opened in this part of the border-land between the disciplines of geology and physics are the “radio-thermal geology” [July, 1909, see 1 of “References” at end of paper] and all that is connected with the use of the radioactive disintegration clock, for the age-determination of rocks and minerals [2]. In structural geology, not unlike to recent biological uses of radioactive material, their “tracer” properties were helpful. Changes in Radon concentration in soil-air, especially accumulations, led to hidden crevices and fault-zones. High contents of Radon in spring-water gave clues as to the types of rocks they had flowed through [3, 4]. One specific application of the small admixtures of radioactive material, however, has only lately found some attention and that is their use in linking beds of sedimentary strata otherwise only poorly identified because of the lack of fossils or other characteristic properties. To be useful for this purpose, two conditions have to be fulfilled; (1) The amount of radioactive material per unit-weight of rock in a given horizon should be uniform over a large area; (2) this same amount should change fairly rapidly in the vertical succession of layers.

Seismology has moved in recent years into the foreground of geological research. The contacts between the two scientific fields are numerous and important as recently demonstrated by Macelwane [see 1 under section “References” at end of paper]. While structural geology could get reliable data from the seismological records, dynamic geology has been benefited with comparatively few facts. We have, however, to visualize that the earthquakes are evidence of acting geological forces. Although all geological events are customarily gaged in a scale of millions of years, it may be stated that the slow and imperceptible, mostly even unmeasurable, geological process culminates frequently in earthquakes which are events accessible to observation— sometimes too fatally obvious.

The determination of the color of the sky entered into modern meteorology with the introduction of the Blue-Scale by Linke and Ostwald [see 1 of references at end of paper], although de Saussure [2] had already made observations of that kind. The intimate relation between the blue color of the sky and the turbidity within the atmosphere, hence with such important elements as the intensity of radiation, the suspended impurities, and the visual range, made surveys of the sky-color desirable. The blue-scale, consisting of a set of cardboards with different shades of blue, is a very handy and cheap device, but its usefulness suffers from certain difficulties in operation. The matching of scale and sky-blue, in particular, often makes trouble, because of the discontinuities in the steps of the cardboard-scale. A simple instrument was therefore constructed, replacing the cardboard-scale by a glass-wedge. This wedge, made of the Signal Blue No. 556 of the Corning Glass Works, had its maximum transmission at about 425 millimicrons. It was movable by a sledge across an eyepiece, so that half of the field was open to the sky. The wedge was illuminated by a mirror, which reflected the sunlight. The thickness of the wedge varied from 0.025 to 0.584 cm on a length of 15.3 cm. In our observations a thickness of 0.23 cm was rarely exceeded to match the sky-blue. By mounting the instrument on a support with graduated circles the azimuth and altitude for each measurement could be determined.