At 21:50 -0400 29/08/2002, [EMAIL PROTECTED] wrote: >The article has a good picture of the "cercle repetiteur", which also appears >on page 41 of L'Aventure du Metre, but I can not figure out how it works. >Somebody, tell me how it works; what is repeated?
At 22:52 -0400 29/08/2002, David Owen wrote: >Robert: He doesn't explain it at all well in the book, and I'm sure I don't >completely understand it. Here goes, though: The two scopes on the repeater >are focused on separate targets, then locked in place on the graduated >circle. The angle between the scopes, as shown on the circle's graduated >scale, is noted. The circle is then rotated to the right, so that the scope >that initially focused on the lefthand target is now focused on the >righthand target, and the angle between them is maintained. The new reading >is noted as well. The other scope is then decoupled and turned back to >focus on the lefthand target, and the first step is repeated. Doing this >several times produces a cumulative reading of the angle separating the two >targets, and that number is then divided by the number of repetitions. Quite correct. By the way, the "cercle r�p�titeur" was developed by Jean-Charles Borda, an interesting character : he was a soldier, a mariner, a naval architect, and also a physicist and astronomer. Plus a politician! >The >final result is therefore an average. Again, correct. This explains the attraction of the "grade" and the centesimal degree of angle to the physicists of the time: using decimal figures for the angles made the calculation of average much easier. Strangely however, Delambre and Mechain translated the final results of their measures in sexagesimal figures before presenting them to the international commission in charge of verifying them. Louis
