The total eclipse of July 18, 1860, was observed in Spain, and photography was for the first time _systematically_ employed in its observation.[7] In the photographs taken the stationary appearance of both the corona and prominences with respect to the moving moon, definitely confirmed the view already put forward that they were actual appendages of the sun. The eclipse of August 18, 1868, the total phase of which lasted nearly six minutes, was visible in India, and drew thither a large concourse of astronomers. In this eclipse the spectroscope came to the front, and showed that both the prominences, and the chromospheric layer from which they rise, are composed of glowing vapours--chief among which is the vapour of hydrogen. The direct result of the observations made on this occasion was the spectroscopic method of examining prominences at any time in full daylight, and without a total eclipse. This method, which has given such an immense impetus to the study of the sun, was the outcome of independent and simultaneous investigation on the part of the French astronomer, the late M. Janssen, and the English astronomer, Professor (now Sir Norman) Lockyer, a circumstance strangely reminiscent of the discovery of Neptune. The principles on which the method was founded seem, however, to have occurred to Dr. (now Sir William) Huggins some time previously. The eclipse of December 22, 1870, was total for a little more than two minutes, and its track passed across the Mediterranean. M. Janssen, of whom mention has just been made, escaped in a balloon from then besieged Paris, taking his instruments with him, and made his way to Oran, in Algeria, in order to observe it; but his expectations were disappointed by cloudy weather. The expedition sent out from England had the misfortune to be shipwrecked off the coast of Sicily. But the occasion was redeemed by a memorable observation made by the American astronomer, the late Professor Young, which revealed the existence of what is now known as the "Reversing Layer." This is a shallow layer of gases which lies immediately beneath the chromosphere. An illustration of the corona, as it was seen during the above eclipse, will be found on Plate VII. (A), p. 142. In the eclipse of December 12, 1871, total across Southern India, the photographs of the corona obtained by Mr. Davis, assistant to Lord Lindsay (now the Earl of Crawford), displayed a wealth of detail hitherto unapproached.