The course of
operations is described in my printed Paper: the original maps,
curves, and graphical projections, are in the bound MSS.: 'Correction
of Compass in Iron Ships--"Rainbow,"' at the Greenwich
Observatory. The angular disturbances were found on July 26th and
30th, requiring some further work on a raft, so that they were finally
worked out on Aug. 11th. I struggled hard with the numbers, but should
not have succeeded if it had not occurred to me to examine the
horizontal magnetic intensities. This was done on Aug. 14th, and the
explanation of the whole was suggested at once: graphical projections
were made on Aug. 16th and 17th for comparison of my explanation with
observations, and the business was complete. On Aug. 17th and 18th I
measured the intensity of some magnets, to be used in the ship for
correction. It is to be remarked that, besides the effect of polar
magnetism, there was no doubt of the existence of an effect of induced
magnetism requiring correction by other induced magnetism: and
experiments for this were made in the Magnetic Observatory. All was
ready for trial: and on Aug. 20th I carried my magnets and iron
correctors to Deptford, mounted them in the proper places, tried the
ship, and the compass, which had been disturbed 50 degrees to the
right and 50 degrees to the left, was now sensibly correct.
Pages:
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224