|
|
Alabaster Blue Sectory 20
Page 11
The largest telescopes at present in existence are _reflectors_. It is much easier to construct a very large mirror than to construct a very large lens; it is also cheaper. A mirror is more likely to get out of order than is a lens, however, and any irregularity in the shape of a mirror produces a greater distorting effect than in a lens. A refractor is also more convenient to handle than is a reflector. For these reasons great refractors are still made, but the largest of them, the great Yerkes' refractor, is much smaller than the greatest reflector, the one on Mount Wilson, California. The lens of the Yerkes' refractor measures three feet four inches in diameter, whereas the Mount Wilson reflector has a diameter of no less than eight feet four inches.
The mastiff is a large, grave, sullen-looking dog, with a wide chest, noble head, long switch tail, bright eyes, and a loud, deep voice. Of all dogs this is the most vigilant watcher over the property of his master, and nothing can tempt him to betray the confidence reposed in him. Notwithstanding his commanding appearance, and the strictness with which he guards the property of his master, the mastiff is possessed of great mildness of character, and is very grateful for any favors bestowed upon him. I once went into the barn of a friend where there was a mastiff chained; I went up to the dog and patted him on the head, when out rushed the groom from the stable exclaiming, "Come away, sir! He's dangerous with strangers." But I did not remove my hand nor show any fear. The consequence was, that the dog and I were the best of friends; but had I shown any fear, and hastily removed my hand, I might have fared rather badly, for this dog always couples fear with guilt.
The men agreed to this. As I could not trust any of them, I took the precaution to take along with me all my notebooks and the maps I had made of the entire region we had crossed, four hundred glass negatives which I had taken and developed, a number of unexposed plates, a small camera, my chronometer, one aneroid, a sextant, a prismatic compass, one other compass, and a number of other things which were absolutely necessary. The rest of the baggage I left at that spot. I begged the men to take special care of the packages. All I asked of them was to prop them up on stones so that the termites and ants should not destroy my possessions, and to make a shed with palm leaves so as to protect the packages as much as possible from the rain. The men promised to do all this faithfully. We drew lots as to who were to be the two to accompany me on the difficult errand across the virgin forest. Fate selected Filippe the negro and Benedicto, both terribly ill.
|
bravenet.com