Ixx Introduction to the Makerstoun Observations, 1845 and 1846. 



The observations of September 11 and 13, made at three distances only, were 

 reduced by the formula 



m Ai g + A,> )8 + A3 7 

 X ~ a + /3 + 7 



where 



a = 1, J P — 7, 5 



Ai = I r^ sin Mj, A2 = ^ r^ sin M2. 



g? - g.,2 111 



gs^ n '■2 n 



^% — k **3^ sin «3 



The observations of vibration were made in the usual manner, the following is 

 a specimen of the details : — 



Table 16. Observations for the Time of Vibration of the Collimating Deflector M, 



- June 15, 1847. 



North End of Magnet moving East. 



North End of Magnet moving West. 



No. 



of 



Vib. 



Time of 

 Transit. 



No. 



of 



Vib. 



Time of 

 Transit. 



Time of 



300 



Vibrations. 



No. 



of 



Vib. 



Time of 

 Transit. 



No. 



of 



Vib. 



Time of 

 Transit. 



Time of 



300 



Vibrations. 







6 



12 



18 

 24 

 30 

 36 

 42 

 48 

 54 



h. m. s. 



6 21 41-5 

 22 12-0 



22 42-4 



23 131 



23 43-5 



24 14-0 



24 44-5 



25 15-0 



25 45-5 



26 16-1 



300 

 306 

 312 

 318 

 324 

 330 

 336 

 342 

 348 

 354 



h. m. s. 



6 47 6-2 



47 368 



48 7-1 



48 37-7 



49 8-2 



49 38-7 



50 91 



50 39-6 



51 10-1 

 51 40-6 



m. s. 



25 24.7 

 24-8 

 24-7 

 24-6 

 24-7 

 24-7 

 24-6 

 24-6 

 24-6 

 24.5 



3 



9 

 15 

 21 

 27 

 33 

 39 

 45 

 51 

 57 



b. m. s. 



6 21 56-8 

 22 27-3 



22 57-8 



23 28-3 



23 58-8 



24 29-3 



24 59-6 



25 30-3 



26 0-7 

 26 31-4 



303 

 309 

 315 

 321 

 327 

 333 

 339 

 345 

 351 

 357 



h. m. s. 



6 47 21-7 



47 520 



48 22-5 



48 530 



49 23.3 



49 54.0 



50 24-4 



50 55-0 



51 25-5 

 51 560 



ni. s. 



25 24-9 

 24-7 

 24-7 

 24-7 

 24-5 

 24-7 

 24-8 

 24-7 

 24-8 

 24-6 



The observations of vibration were reduced by the formula already given {In- 

 troduction^ p. xxi). The formula for the time of vibration with the ring [Introduc- 

 tion^ p. xxii*), having the more convenient form 



T,' = T-/ (1 - if - 86I00)' (1 - */^^^^ " '/^^^ + *) 



The values of K the moment of inertia have been deduced by the formulae al- 

 ready given, pages xxi and xxiv. The times of vibration and the dimensions of the 

 rings are given, page 352. 



The following are the results of the observations with the circle magnetometers :— 



* See Corrigenda. 



