1874.] Atomic Matter and Luminiferous Ether. 187 
in the same times. Vibrations at right angles may there- 
fore have some connection, as on the principle of the well- 
known parallelogram of forces. 
All radiating vibrations which absorb energy in their 
beginning, and evolve it when they are arrested, necessarily 
follow the same law, of effects lessening in proportion to the 
square of the distance from the centre of radiation. The 
effects of gravity are therefore consistent with its being a 
force due to radiant vibration. 
Before quitting this point of the question, the veloci- 
ties at which vibrations are known to be transmitted 
through matter require some notice. The ordinary 
surface-wave on water (a vibration across the line of 
progression) moves with a velocity of about 1 foot per second. 
The waves of light, vibrations of the same kind, pass 
through water with a velocity probably as corre¢tly repre- 
sented by 200,000 miles a second. And eletricity passes 
through some metals still more rapidly. The waves of sound 
(to-and-fro vibrations in the line of progression) pass through 
water with a velocity of about 4000 feet per second. As there 
are certainly two varieties of transverse vibrations, there may 
be at least two varieties of to-and-fro vibrations, and, if so, 
the velocities of the varieties of each kind may bear the same 
or similar proportion to each other, and the velocity of 
transmission of the vibrations of gravity may probably be 
at least 4000 times as rapid as those of light. 
The medium between atoms has to serve for the pheno- 
mena belonging to latent or potential energy, or the energy 
of position. This energy is of two kinds: one as whena 
weight is raised; the other kind such as a coiled or bent 
spring possesses. 
The sunbeam reaches us, say, eight minutes after it left 
the sun. The waves of light present to us at any instant 
are so disconnected with others before and after them that 
both or either might be arrested without our immediate 
knowledge. In fact, as the earth sweeps on its course it 
cuts into fresh lines of waves, and leaves broken lines to 
continue their course. Each spot on the earth receives 
part only of one of the lines of waves of light reaching 
from the sun, and a still smaller proportion of the lines of 
those waves whose sources are the sun’s we call fixed stars. 
A floating straw is moved on a pond’s surface by the waves 
proceeding from a stone, which fell at a distance, some time 
before ; and, although the spot where the stone fell is still, 
the straw moves. 
All radiated vibrations follow the same rule, and “‘ energy 
