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believe that it would be ‘ indifferent’ if we were to start the sun off in a 
right line at the rate of 65,000 miles an hour.” No ; by no means. Nobody 
supposes it would be indifferent if, the sun being now at rest, and the exist- 
ing motions of the heavenly bodies being what they are, we were now to 
start the sun off at the rate of 65,000 miles an hour. That is a very 
different question. But it is of no consequence, and will not affect the 
results obtained, if we suppose that the whole solar system is moving con- 
jointly at the rate of 65,000 miles an hour, or at any other rate. (Hear, 
hear.) It would make all the difference, however, if you were now to start 
the sun at that velocity, and not start the other bodies in the same 
direction 
Mr. Reddie. — I am letting you suppose that they have all been going 
together, but say that they couldn’t do so by the same forces as when the sun 
is at rest, which was what Newton supposed. (See § 15, line 24.) 
Mr. Brooke. — Then if they are all supposed to go together, I will simply 
say that I believe firmly that it would be quite indifferent. I am obliged, of 
course, to omit a great many points ; but in § 19 he says, “ It is part of 
this teaching that stars of the second magnitude, that is, stars only less 
bright than Sirius, must have been shining in the firmament for twenty-eight 
years before they were visible on the earth ; and that the smallest stars 
visible to the naked eye must have been invisible for 138 years. The 
converse absurdity has also been taught, that if such stars ceased to exist? 
they would continue as visible stars to earthly eyes and telescopes for twenty- 
eight years and 138 years respectively after their non-existence!” Now, I 
simply mean to say that there is no absurdity in this at all ; and I will in a few 
words reduce it to his comprehension. Did any one of you ever see a stone 
dropped into the surface of a still pond and notice the effect ? You see some 
little waves — some little undulations travelling off ; but after a very short 
time the point where the stone was thrown in becomes absolutely at rest. 
But there the little batch of waves goes travelling on and on to an indefinite 
extent according to the extent of the lake or sheet of water. It may become less 
and less visible, but it is still visible to a great distance. Again, I would ask 
Mr. Reddie, did he ever hear an echo ? If a short sudden sound is made, as 
by a whistle or the blowing of a horn 
Mr. Reddie. — I was discussing not sound, nor even light, but sight. 
Sound or light can go round a corner ; but you cannot see objects so. (Hear, 
hear.) 
Mr. Brooke. — Wait for my point. What takes place in that case ? A 
batch of waves is sent off through the air ; these waves strike an object at a 
distance ; they are reflected at that distance and come back again to you, 
and that batch of waves then produces upon the ear the impression of sound. 
Now the case is precisely analogous with regard to light. No one that I 
am aware of doubts in the present day that light consists of undulations, of 
vibratory motion of matter of some kind. If that be the case, it is just the 
same with regard to sound or waves on the surface of a pond. If a body is 
luminous it has the power of setting in motion these undulations ; and, 
