Total eclipses of the sun permit of three main types.of research. First, research, relative io the astronomy of position," the exact hours of contact Which make it possible to correct the elements concerned with the move. ment of the moon. This type of asearch loses much of Its interest as study of occultations of stars by the moon are preferred because of the fact, that they are more numerous and produce equivalent results, studies from the type of research prow ts by total eclipses of the sun. In particular, study is made of the outer layers of the sun, low chromosphere, and above all the reversing layer and specially observations of the flash spectrum, which is the spectrum furnished by the thin crescent, of the sun just before the beginning or just after the end of totality, There is thus a medium whereby the approxlmate altitudes can be determined of the various layers surrounding the in—and particularly the study of calcium and hydrogen.
'But the most important question of all concerns the study of the corona, 'Without doubt, the study of the flash spectrum can' be made more often when astronomers have at their dis-[Basal instruments similar to those at Mount Wilson, which bring the ima of the sun up to 42 centimetres in diameter and consequently lose by that feet, much of the Interest at the time of eclipses; without question, i recent years, photographs have been made, together with observations, in clear periods, of the lower layers of the corona,
Text read from the printed page and cleaned; old type leaves the occasional error.