Page:Popular Science Monthly Volume 11.djvu/557

Rh the last few years been manifest in various brilliant discoveries. To show this, it will be sufficient to describe briefly the situation of each observatory, and the work upon which it is at present engaged.

Director, M. Cacciatore; Astronomer, M. Tacchini.—This observatory contains two important instruments: a meridian-circle, constructed in 1857 by Pistor and Martins (of Berlin), whose telescope has an aperture of 126 millimetres (4.98 inches), and an equatorial by Merz (of Munich), of 24 centimetres (9.45 inches) aperture, which, though built in 1857 was not mounted until 1865. The meridian-circle was employed in 1870 to determine the difference of longitude between Naples and Palermo, this last point being the fundamental station in the new topographical map of Sicily, and it is daily employed in observations of the sun and the principal stars. The most important work, however, of the observatory of Palermo, which is specially undertaken by M. Tacchini, is the daily study of the solar protuberances.

Since the total solar eclipse of 1868, a great number of astronomers have devoted themselves to the daily observations of these protuberances, in order to study their distribution on the solar circumference, and their relations with solar spots. Among these astronomers are Lockyer, Secchi, Rayet, Respighi, Tacchini, and Young, but it is in Italy that these researches are most vigorously prosecuted, and, in order to avoid the interruptions in a series which cloudy days may occasion, the observatories of Palermo, Rome, and Padua, prosecute these observations in common.

Every day, when the weather will permit, M. Tacchini makes a drawing of the protuberances surrounding the border of the sun and of the spots and faculæ which are upon its surface. These drawings, as well as those made at Rome and Padua, are subsequently published in the "Memoirs of the Society of Italian Spectroscopists," whose publications, begun in 1872, form already four large quarto volumes.

For this work, M. Tacchini makes use of the large equatorial of the observatory, and a direct-vision spectroscope made by Tauber, of Leipsic, which has two series of five prisms. These prisms are of rare excellence, for, in spite of their number, the spectral lines suffer no distortion. The spectroscope can be rotated on its axis so that it can be placed tangentially on any portion of the sun's circumference. Among the interesting historical instruments of the observatory is the altitude and azimuth circle made by Ramsden in 1788-'89, which served Piazzi in the preparation of his great catalogue of stars.

Director M. de Gasparis; Astronomers, MM. Fergola, Brioschi, and Nobile.—The observatory of Naples is the most important of those of Italy, in its equipment and its personal establishment.

It was founded in 1812 by Murat, and it is built in agreement with