ACCIDENTS IN WORKING 119 



have every reason to believe, original with my father 

 at the time of its construction; as was, I am dis- 

 posed 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." l 



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 Pal- 

 ermo, 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." 2 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, 



1 Weld, Histoi-y, etc., ii. 193. 



2 See especially, Memoirs, p. 168. 



