408 TRANSACTIONS OF SECTION A, 
The following results were obtained : 
. Velocit 
Substance Radius Density eee 2 aeconditle to 
Voges Stokes's formula 
em. : cms./sec, 
Lycoperdon . 0:000207 1:44 0:0465 0:0757 
Polytricum . 0-000478 1:53 0:228 0°417 
Lycopodium , 0 00158 1175 177 3°52 
12. Report on the Magnetic Observations at Falmouth Observatory. 
See Reports, p, 36. 
13. Report on the Geodetic Are in Africa,—See Reports, p. 87, 
14. Highth Report on the Investigation of the Upper Atmosphere by 
Means of Kites.—See Reports, p. 87. 
15. Report of the Committee on Electrical Standards, 
See Reports, p. 38. 
16. Report of the Seismological Commitlee.—See Reports, p. 48. 
17. Report of the Committee to aid in Establishing a Solar 
Observatory in Australia,—See Reports, p, 66. 
TUESDAY, AUGUST 31. 
Discussion on ‘ Earth Tides.’ 
Opened by Professor A. E. H. Love, F.R.S. 
Lord Kelvin showed (1863) that, if the earth could be regarded as 
hcmogeneous and absolutely incompressible and possessed of the same degree 
of rigidity as steel, the oceanic tides of long period would be reduced, owing 
to the yielding of the earth, to about two-thirds of the theoretical heights 
which they would have if the substance were absolutely rigid. Sir G. Darwin 
(1881) estimated the actual height of the fortnightly tide as about two- 
thirds of the theoretical height. Attempts to measure directly the lunar 
disturbance of terrestrial gravity were made by several observers, and 
recently Dr. O. Hecker, by using two horizontal pendulums mounted in an 
underground chamber, has demonstrated the existence of the corporeal tide, 
and has shown that the actual deflexion of such pendulums is about two- 
thirds of what it would be if the earth were absolutely rigid. This result 
means that, besides the tide-raising force of the moon (F), there act on 
the pendulum other forces arising from the deformation of the earth. These 
forces are (i) the component of undisturbed gravity tangential to the 
deformed surface, denoted by hF'; (ii) a genuine disturbance of gravity, 
consisting in the attraction of the tidal protuberance and other related 
