of the Acceleration of Gravity for Tokio, Japan. 295 



in the interval of time shown by the chronometer; and the 

 breaks in the line, counted carefully afterwards by two inde- 

 pendent students, gave the whole number of vibrations of the 

 pendulum in that time. The fraction of a vibration could also, 

 of course, be ascertained by comparing with the length of the 

 lines in the neighbourhood the length of the first line made 

 after the first break had been produced, on tapping the arma- 

 ture, and repeating the same process at the end of the paper. 

 The experiment is, of course, independent of the rate at which 

 the paper runs out, provided, of course, it is never allowed to 

 run so slowly that there is any difficulty in distinguishing the 

 different breaks electrically made by the long vibrating pen- 

 dulum. The mean temperature of the wire was carefully 

 taken at each experiment. A sample of one or two of the 

 many experiments recorded in the students' laboratory note- 

 book follows. 



Number of Experiment 26. — 25th of January, 1878. 



Number of vibrations obtained from counting 1 -i a-i k 3 



on the paper J-IUIO4 



Time taken — observed on the chronometer . Oh. 52m. Os. 

 Mean temperature at the beginning .... 10°*5 C. 



„ „ „ end : 1P-25 C. 



Time of vibration == 3*0744 seconds. 



Number of Experiment 45. — 15th of February, 1878. 



Number of vibrations obtained from counting \ -, qok k 



on the paper J id ™'* 



Time taken — observed on the chronometer . In. 11m. 0s. 

 Mean temperature at the beginning .... 9°*25 C. 



„ „ w< end 12°*25 C. 



Time of a vibration = 3*0745 seconds. 



Number of Experiment 53. — 21st of February, 1878. 



Number of vibrations obtained from counting") 100 o c 



on the paper / 1288 * 5 



Time taken — observed on the chronometer . lh. 6 m. s. 

 Mean temperature at the beginning .... 8°'5 C. 



,1 „ „ end 12°*25 C. 



Time of a vibration = 3*0741 seconds. 



Frequent sun-observations were made to check the rate of 

 the chronometer, which is comparatively easy in Japan, as 

 during the winter there the sun is seen almost daily from sun- 

 rise to sunset. ; 



The next point was to measure accurately the length of the 



