410 Proceedings. 
poles. The central fire theory is based on observed facts. He 
agreed with Mr. Mallett’s observations, and places the depth at 
which rocks would become molten at from twenty to thirty miles 
from the surface. He is supported by the writings of Sir J. 
Herschel, 1866. 
Mr. Carruthers quoted “astronomers and mathematicians,” but did not 
give their names. Mr. Irvine considered that the central fire theory 
completely accounts for all phenomena connected with earthquakes and 
yoleanoes, and is in no way disproved by Mr. Carruthers. He thought that 
Mr. Carruthers’ hypothesis fails when applied to the moon, and does not 
account for the extinct voclanoes and evidence of earthquake action observed 
there. The central fire theory agrees with Le Placis’ nebular hypothesis, 
and fully accounts for the presence of volcanic action in all cosmical bodies. 
Mr. Crawford remarked that, according to Burton, the temperature in 
the mines at Brazil did not increase at the same rate as in mines in other 
parts of the world. : 
Mr. Carruthers, in reply, stated he had brought no proofs that the 
earth’s rotation was retarded, as he had taken the fact for granted. The 
tides must cause or tend to cause such retardation, and the astronomers had 
calculated the amount of it to be that stated in the paper. He had not 
considered it necessary to raise the question. The effect of any retardation 
would be, as stated by Mr. Irvine, to heap up the water of the ocean at the 
poles, and this would, in proportion to the specific gravity of water, a3 
compared with that of earth, counteract the tendency of the crust to break. 
He thought it unnecessary to calculate to what extent this counteracting 
tendency had acted, as we know that the ocean is not heaped up at the 
poles, while the age of the earth is so great that a very large amount of 
elongation of the polar axis must have taken place on account of the retar- 
dation of the rotation. The only fact on which the central fire theory was 
founded was that in mines in Western Europe the heat always increased 
with the depth below the surfaces. As Mr. Crawford stated, in Brazil this 
was not the case, and even in Europe the increase of heat varies so much 
that it cannot be due to any cosmical cause. At Rotomahana it increases 
100° in six inches. Is this a fair measure of the increase of heat at this 
point as we approach the centre of the earth? ‘Yet it is on similar facts 
that the central fire theory rests. Mr. Carruthers contended that the 
increase of heat at Rotomahana and elsewhere is due to the same cause, 
namely, voleanic action. If there really is such a great heat in the inner 
parts, they cannot be formed of any material similar to that of the surface 
rocks, as is shown by the specific gravity of the earth. As to the fact that 
the moon is mountainous, although its velocity of rotation is small, this 
Seog ee ery yen) eee 
Pepe vets Rata 
Te ee Rea te 
