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“ Wrangler” lias altogether left us in the dark as to the mode of accounting 
upon his own system for the exceedingly complicated motions of the planets ; 
and I think that the strongest possible confirmation of current physical 
astronomy is that the planets are not only moving round the sun, but occu- 
pying those positions in the atmosphere which they would do according to the 
current hypothesis. I do not see that Mr. Reddie has refuted in any way the 
differential equation, or the solution of it, which gives you these motions. 
There are two ways of attacking this theory. I do not think we have any- 
thing to do with what Newton said. The way to attack it is to show first 
that the mathematical analysis is not true ; and you may possibly be able to 
do that, for I do not know that it is impregnable. It requires an enormous 
amount of faith to digest the differential calculus ; but, when you have 
digested it, it will account for myriads of phenomena amongst the heavenly 
bodies. But, then, it is fair to state beforehand that the whole of this is not 
so much matter of demonstration as it is supposed to be. (Hear, hear.) 
After all, you put into it all sorts of disturbing calculations. You say you 
will begin with the three bodies, but by-and-by you take one out to put 
another in, so that there is always a little u tinkering” and a little finding out 
that something has been neglected which ought to be taken into considera- 
tion. (Hear, hear.) Then, with regard to the greatest triumph of the 
mathematical planetary theory — the discovery of Neptune, — Mr. Reddie 
brought the matter before this society, supported by the authority of astro- 
nomers of eminence in America, and said that there was the greatest possible 
discrepancy between the elements of Neptune as calculated by Le Yerrier 
and Adams, on the perturbation theory, and the elements as calculated from 
observation since, by Mr. Walker. Therefore I think that, as a matter of 
abstract science, we cannot assert that the discovery of Neptune has demon 
strated the theory of gravitation. 
Mr. Brooke. — I cannot argue that matter without the data. The calculated 
orbits might or might not correspond, but that would not invalidate the fact 
that the position of the body causing the disturbing influence was first 
assigned and then found to be in the place assigned to it. That fact is not 
impugned. 
Admiral Halsted. — I wish to ask Mr. Brooke a question of professional 
interest as to the length of time it takes light to travel to the earth. For 
instance, I get the meridian of the sun at noon. Now, is the light which I 
get into my sextant actually then proceeding from the sun, or has it proceeded 
from the sun long before ? 
Mr. Brooke. — Eight minutes previously. 
Admiral Halsted. — With regard to the question of the stars going out 
when they go down, say I have been taking my observations of a particular 
very distant star, and it has gone down. On the following night I pick it up 
for the same purpose. I look out for that light again. Is there a special law 
with regard to that ? What is the distance of time by which I ascertain 
exactly the variation between the light which I use and that which has left 
the star ? 
