154 LEISURE-TIME STUDIES. 



modern study of earth-science, the geologist is led to recog- 

 nise in the principle of the uniformity of nature the means 

 whereby all physical actions are bound together in one har- 

 monious whole. It so happens that the evidence capable of 

 being adduced from the growth of coral-reefs goes far to 

 prove the constant and uniform state of our earth through- 

 out immense periods of time. The testimony of Mr. Dana 

 with regard to the rate at which coral grows is to the effect 

 that the massive corals on which the increase of reef depends 

 are of very slow growth ; the branching and certain other 

 kinds growing at a faster rate. One-eighth of an inch per 

 year is given by this author as " the average upward increase 

 of the whole reef-ground per year;" and the estimate 

 appears to be a perfectly just one, when judged by the 

 evidence afforded us of the rate of growth in corals. All 

 authorities agree in stating the growth of massive corals at a 

 very low rate, and the time which has been occupied in the 

 formation of a reef 2000 feet thick must, therefore, on Mr. 

 Dana's estimate, be set down at 192,000 years. This com- 

 putation, it must be remembered, is one dealing with 

 the work of modern corals. In the far-back past, coral- 

 reefs existed similar in every respect to their modern 

 representatives ; these fossil-reefs in many cases evincing 

 an immense thickness. Hence we are led to believe 

 that, notwithstanding the alteration which our earth has 

 undergone, it has had prolonged periods of rest; and 

 the existence of a modern coral-reef may therefore afford 

 evidence, not only of the immensity of past time, but also 

 of the uniformity of nature's ways and works during periods 

 compared with which the furthest limits of history and even 

 of man's own age, are but as yesterday. The deductions 

 from a study like the present may be fitly expressed in 

 Laugel's words, as giving us " a higher conception of the 

 universe than that entertained by the ancients ; " since 

 science "no longer regards the material world as the play- 

 thing of mere caprice," but " embraces the past, the present, 

 and the future in a magnificent unity, outside of which 

 nothing can exist." 



