Out of the _dark_ eclipses recorded, perhaps the best example is that of May 18, 1761, observed by Wargentin at Stockholm. On this occasion the lunar disc is said to have disappeared so completely, that it could not be discovered even with the telescope. Another such instance is the eclipse of June 10, 1816, observed from London. The summer of that year was particularly wet--a point worthy of notice in connection with the theory that these different appearances are due to the varying state of our earth's atmosphere. Sometimes, indeed, it has happened that an eclipse of the moon has partaken of both appearances, part of the disc being visible and part invisible. An instance of this occurred in the eclipse of July 12, 1870, when the late Rev. S.J. Johnson, one of the leading authorities on eclipses, who observed it, states that he found one-half the moon's surface quite invisible, both with the naked eye and with the telescope. In addition to the examples given above, there are three total lunar eclipses which deserve especial mention. 1. A.D. 755, November 23. During the progress of this eclipse the moon occulted the star Aldebaran in the constellation of Taurus. 2. A.D. 1493, April 2. This is the celebrated eclipse which is said to have so well served the purposes of Christopher Columbus. Certain natives having refused to supply him with provisions when in sore straits, he announced to them that the moon would be darkened as a sign of the anger of heaven. When the event duly came to pass, the savages were so terrified that they brought him provisions as much as he needed. 3. A.D. 1610, July 6. The eclipse in question is notable as having been seen through the telescope, then a recent invention. It was without doubt the first so observed, but unfortunately the name of the observer has not come down to us. CHAPTER X THE GROWTH OF OBSERVATION The earliest astronomical observations must have been made in the Dawn of Historic Time by the men who tended their flocks upon the great plains. As they watched the clear night sky they no doubt soon noticed that, with the exception of the moon and those brilliant wandering objects known to us as the planets, the individual stars in the heaven remained apparently fixed with reference to each other. These seemingly changeless points of light came in time to be regarded as sign-posts to guide the wanderer across the trackless desert, or the voyager upon the wide sea.