THE PROBABLE AGE OF THE WORLD. 649 



MODERN philosophers on the probable age 



OF THE WORLD. 1 



A SHORT time ago Sir William Thomson took occasion, at a 

 meeting of the Geological Society of Glasgow, to make a some- 

 what startling statement. He said that the tendency of British popu- 

 lar geology was, at the time he spoke, in direct opposition to the 

 principles of natural philosophy. 



So strong an opinion expressed by the man who is, perhaps, fore- 

 most in this country in applied mathematics and natural science, 

 naturally attracted great attention, and it is not too much to say that 

 in the six years which have since elapsed a very great change has 

 taken place in the views of those best able to form an opinion on the 

 subject of Sir William Thomson's animadversions. 



Whether or not we are correct in saying that such a change has 

 actually taken place in educated public opinion, it is the object of this 

 paper to show; but we may at least affirm at the outset, without fear 

 of contradiction, that a very smart conflict has been raging on the sub- 

 ject in the scientific world. The opposing forces are the geologists and 

 the mathematicians. There has been hard hitting on both sides, and 

 no quarter given. Of late the mathematicians have brought up their 

 reserve, a contingent of natural philosophers, who have clone good 

 service. The latest intelligence from the seat of war speaks of a sus- 

 pension of hostilities. The mathematicians will make no concessions, 

 but the geologists appear likely to abate somewhat of their high de- 

 mands. There is even some talk of an amalgamation of the opposing 

 armies. In plain English, there has been a dispute as to the age of 

 the world. Geologists declared that the centuries of its duration 

 could only be denoted by an array of figures so large as to paralyze 

 the reasoning faculties and convey no definite impression to the mind. 

 Other branches of science have shown cause for attributing to the 

 solar system a limit of duration, vast indeed, but not absolutely in- 

 conceivable. 



To those whose interest in such matters is literary rather than 



1 1. "Lectures on some Recent Advances in Physical Science." By Prof. P. G. Tait, 

 Professor of Natural Philosophy in the University of Edinburgh. 1876. 



2. " On Geological Dynamics." By Sir William Thomson, LL. D., F. R. S. " Trans- 



actions of the Geological Society of Glasgow," 1869. 



3. "On Geological Time." By Sir William Thomson, LL. D. "Transactions of the 

 Geological Society of Glasgow." 1868. 



4. " Sur le Ralentissement du Mouvement de Rotation de la Terre." Par M. Delaunay. 

 Paris, 1866. 



5. "Climate and Time." By James Croll. " H. M. Geological Survey of Scotland." 

 London, 18*75. 



6. " Principles of Geology." By Sir Charles Lyell. Fourteenth edition. London, 1875. 



