66 _ PROFESSOR C. V. BOYS ON THE 
funnel-shaped end to the pipe. This did not work, and I was therefore compelled at 
the time to produce the draught by some ready means; gentle movement of a sheet 
of paper at a distance from the instrument produced the desired motion, but my 
going near the instrument at all was essentially bad. The periods obtained after . 
this were :— 
Oct. 29 . . . 241°99 + position. 
Pane er OO = 
30. 6h a a Qhiesees oe ae 
Ge Gg OURO Se Se eee 
I noticed slight differences between periods taken with the lead balls in the + and 
— positions with my preliminary apparatus, but, though I am not able to explain it, 
I am glad to say that, with the more perfect setting and screening now in use, it has 
practically disappeared. The two periods taken with the counterweight gave identical 
results, 64°954 seconds. 
The soldered fibres used in all the later experiments seem a definite improvement, 
as the creeping of the zero, which was never very troublesome, almost entirely ceased. 
The traffic and the trains are not the only causes of disturbance. Wind, by 
pressing upon the building and neighbouring trees, of course shakes the ground ; but 
on Sept. 9-10, a particularly quiet night, I had to leave, owing to a sudden dis- 
turbance produemg a pendular motion of 15 divisions, or 150 units, and for some time 
there was no quiet. As the motion was clearly produced by a lurch of the whole 
instrument and table carrying it, and was greater in amount than any traflic in the 
busiest part of the day had ever produced, and was moreover free from the high 
period tremor characteristic of human disturbance, I at once set it down to an earth- 
quake. I was marking transits of every 10 divisions at the time. The moment of 
the last mark was 15h. 44m. 14°3s., allowing for the error of the clock as determined 
at the Observatory. The next mark was due in 3 seconds, but I was, of course, 
unable to record it. In the ‘Standard’ of Sept. 12th there was an account of a 
violent earthquake at Jassy, which was felt also at Bucharest, at six o’clock in the 
morning. I have not ascertained the exact time at which the earthquake was felt in 
Xoumania, or the amount to allow for difference of longitude, but these, no doubt, 
can be supplied from Vienna.* 
Experiment 11 was a purely comparative one. Everything being left as in Experi- 
ment 10, a tube was connected with the stop-cock in the bell-jar J, and with a 
hydrogen bottle and drying bottle, so that dry hydrogen could be fed in to displace 
the air in the central tube. The object was to see if any advantage would be derived 
from the smaller viscosity of hydrogen ; but, though the resistance fell so as to change 
* Mr. C#artes Daytson informs me that the shock was recorded at Bucharest at 3h. 40m. 35s., a.M., 
but that the epicentrum must have been some distance from there. The time interval between Bucharest 
and Oxford appears very small, the usual rate of travel being 3 km. a second, or a little more. 
