52 REPORTS ON THE STATE OF SCIENCE. 
particular group of records to which we refer are given-in the accom- 
panying table. The entry of July 5 may have been recorded at Gottingen, 
but with this exception the remaining disturbances do not appear in 
registers from Gottingen, Strassburg, or Laibach. The difference in 
the number of records obtained at different stations where the instruments 
are of one type, viz., that adopted by the British Association, partly 
finds an explanation in differences in foundation, see p. 60. The 
reasons that stations provided with apparatus of the Reuber-Ehlert type 
do not appear to pick up very small movements is possibly due to a 
want of definition in the photographic trace; but here again the question 
of foundation cannot be overlooked. Directly we come to apparatus 
where the record is obtained upon a smoked surface, which is the case 
at many European and American stations, a new factor has to be con- 
sidered. The slight freedom in the connections between the joints of 
multiplying indices, and the elasticity of the same, suggests a loss of 
motion, the result being that the writing pointers do not move until a 
certain amplitude of earth movement has been reached. Whether this 
explanation be correct or not, my own experience is that instruments 
writing on a smoked surface, although they may yield excellent seismo- 
grams of a large earthquake, are very unsatisfactory as recorders of very 
slight disturbances. Records of large earthquakes may be obtained by 
many types of instruments, but directly we wish to record feeble move- 
ments at considerable distances from their origin, the best results appear 
to come from the instrument adopted by the British Association with the 
photographic surface moving at the rate of about 240 mm. per hour. As 
illustrative of this we find that the number of records obtained at Shide, 
Hamburg, Gottingen, and Laibach between January 1 and April 30 of 
this year were respectively 98, 65, 61, and 33. At the first of these 
stations the instrument employed is of the B.A. type, whilst at the three 
latter stations records are obtained on smoked paper or by photographic 
arrangements with a high multiplication. All the records referred to 
were noted at more than one station, and therefore their reality as repre- 
senting widespread-earth disturbances cannot be doubted. The number 
of records obtained at Bidston, Kew, and Edinburgh, where the photo- 
receiving surface only moves at the rate of 60 mm. per minute, were not 
so numerous as those obtained at Shide. 
After-shocks of the Jamaica Earthquake apparently recorded in Great Britain. 
| Date ah land Shide Kew Bidston Paisley | Edinburgh 
1907 | | : 
| Jan.15.. 0.55 — — _ —_ 0.48? 
‘5 : 1.53 1.52 a 1.52 — — 
i 2.52 2.53 —_ 2.52 2.52 | 2.48 
*) 3.50 3.51 _ 3.51 esol 
nS 5.5 5.4 ~ 4.587? _— ~ 
” 7.30 7.40 — 7.27 7.25 7.25 
” 8.50 8.50 8.44 8.52 8.50 — 
8 9.20 9.19 9.29 9.19 — 9.21 
5 11.50 11.45 — 11.43 11.45 — 
” 15.50 15.45 —- | = 15.45 — 
” 17.15 17.14 _ 17.14 17.15 _ 
” 17.48 18.12 17.48 18.16 18.12 o- 
” -| 21,52 — _ — = — 
