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Rh have every reason to believe, original with my father at the time of its construction; as was, I am disposed to think, also the system of triangular arrangement adopted in the woodwork, being a perfect system of 'diagonal bracing,' or rather that principle to which the 'diagonal bracing' system owes its strength.

"The other mirror and the rest of the polishing apparatus are on the premises, but in a situation adapted only for preservation, and neither for use nor inspection. The iron grinding tools and polishers are placed underneath the tube, let into the ground, and level with the surface of the gravelled area in which it stands."

The duty of attending to machinery and mirrors, in an observatory such as Herschel's, was not free from danger. Even visitors had to take the risk of an accident in satisfying their curiosity. Piazzi of Palermo, the discoverer of the first asteroid, "did not go home without getting broken shins," Caroline writes. And she adds, "I could give a pretty long list of accidents which were near proving fatal to my brother as well as myself." One of these accidents she does record. It was on December 31, 1783: "The evening had been cloudy, but about ten o'clock a few stars became visible, and in the greatest hurry all was got ready for observing. My brother, at the front of the telescope, directed me to make some alteration in the lateral motion, which was done by machinery, on which the point of support of the tube and mirror rested. At each end of the machine or trough was an iron hook,