The parallel between Biology and Geology, which I have drawn, is further illustrated by the modern growth of that branch of the science known as Petrology, which answers to Histology, and has made the microscope as essential an instrument to the geological as to the biological investigator. The evidence of the importance of causes now in operation has been wonderfully enlarged by the study of glacial phenomena; by that of earthquakes and volcanoes; and by that of the efficacy of heat and cold, wind, rain, and rivers as agents of denudation and transport. On the other hand, the exploration of coral reefs and of the deposits now taking place at the bottom of the great oceans, has proved that, in animal and plant life, we have agents of reconstruction of a potency hitherto unsuspected. There is no study better fitted than that of geology to impress upon men of general culture that conviction of the unbroken sequence of the order of natural phenomena, throughout the duration of the universe, which is the great, and perhaps the most important, effect of the increase of natural knowledge. THE END. FOOTNOTES: [A] There are excellent remarks to the same effect in Zeller's _Philosophie der Griechen_, Theil II. Abth. ii p. 407, and in Eucken's _Die Methode der Aristotelischen, Forschung_, pp. 136 _et seq_. [B] Fresnel, after a brilliant career of discovery in some of the most difficult regions of physico-mathematical science, died at thirty-nine years of age. The following passage of a letter from him to Young (written in November 1824), quoted by Whewell, so aptly illustrates the spirit which animates the scientific inquirer that I may cite it: 'For a long time that sensibility, or that vanity, which people call love of glory is munch blunted in me. I labor much less to catch the suffrages of the public than to obtain an inward approval which has always been the mental reward of my efforts. Without doubt I have often wanted the spur of vanity to excite me to pursue my researches in moments of disgust and discouragement. But all the compliments which I have received from M.M. Arago, De Laplace, or Biot, never gave me so much pleasure as the discovery of a theoretical truth or the confirmation of a calculation by experiment.' [C] 'Memorable exemple de l'impuissance des recherches collectives appliquees a la decouverte des verites nouvelles!' says one of the most distinguished of living French _savants_ of the corporate chemical work of the old Academie des Sciences. (See Berthelot, _Science et Philosophie_, p. 201.)