Page:Popular Science Monthly Volume 67.djvu/301

Rh The principal work of preparation was accomplished nearly a week before the eclipse. The remaining time was devoted to arranging the final details and to training the assistants. As soon as it was known that help would be needed to make the observations, it was tendered in abundance by the Dutch residents. Fifteen, including several of the army officers, and the general manager of the government railways, were invited to assist. The observations with each instrument were very minutely planned. Every motion to be made by each observer was carefully considered and arranged beforehand, and numerous rehearsals enabled the operations of taking the photographs to be performed with certainty and great rapidity.

Although light clouds covered the sun during totality, the resulting observations were very successful and yielded much important information. Photographs were secured with three sets of cameras especially designed to record the inner, middle and outer corona. The large-scale photographs of the inner corona showed a peculiarly disturbed region, which later was found to have been at the time of the eclipse above a group of sun spots. The inference that there was a close connection was irresistible.

This eclipse was particularly favorable on account of the great duration of totality—six and one-half minutes—for the search for any planets between Mercury and the sun. Four cameras of long focus were especially designed for the search. They were capable of recording any such objects as faint as the ninth magnitude. The photographs were taken in duplicate to guard against defects. They covered a region 6° wide and 30° long, in the direction of the sun's equator, as the most probable orbit of such a planet would lie in that region. Although the search was not so complete as desired, owing to the clouds, our knowledge was considerably extended. In two thirds of this area, stars fainter than the eighth magnitude were photographed and in the remaining third, stars of sixth magnitude and brighter. All the objects on the plates were identified as known stars. It is practically certain from the observations, therefore, that there is no such planet as bright as fifth magnitude, and little probability of there being any as bright as eighth magnitude. A planet thirty miles in diameter in the region searched would appear as a star of the eighth magnitude. To account for the observed deviations of Mercury from its computed orbit would require over half a million bodies 30 miles in diameter and as dense as Mercury.

Another investigation undertaken concerned the nature of the coronal light. The bright coronal lines observed at previous eclipses showed that a small portion, at least, of the light was due to incandescent gases. But the great portion of the light gave a spectrum which appeared to be perfectly continuous. Some observers had