[61]. Of course, Mr. Wallace does not believe that it is actually 200,000,000 years since the Cambrian period.
[62]. World Life, p. 196.
[63]. World Life, p. 72.
[64]. Correlation of Physical Forces, p. 164 (fifth edition), 1867.
[65]. Popular Science Monthly for January 1873.
[66]. See also on this point Mr. Lockyer’s “Bakerian Lecture,” Proc. Roy. Soc. No. 266, p. 21.
[67]. Proc. Roy. Soc. vol. xxviii. p. 160.
[68]. Proc. Roy. Soc. vol. xxxii. p. 230.
[69]. Ideal Chemistry, p. 56.
[70]. American Journal of Science, vol. xxiii. p. 124.