PROGRESS OF HUMAN KNOWLEDGE. 13 



ledge of tlie fossil world, vast though its scope and 

 attainments now are, has grown up in the course of a 

 single lifetime. When I was at Edinburgh, from 1809 

 to 1811, an angry contest existed between the Plutonian 

 and Neptunian schools of Geology. The ' Ossemens 

 Fossiles' of Cuvier had been published a few years 

 before ; but this great topic scarcely found place in 

 the controversy. Its value as an index to geological 

 ages and successions was barely understood, and its 

 future greatness as a science wholly unseen. 



The term prediction, in its strict sense, belongs 

 almost exclusively to the science of our own day. 

 Except in a few astronomical phenomena, the know- 

 ledge of the ancients never reached to this highest ex- 

 pression of intellectual power and progress. The 

 faculty of predicting, through known phenomena, 

 others yet unseen and unknown, needs no epithets to 

 mark its import. It is, in fact, the nearest approach 

 made to those higher laws through which the Creator 

 acts in the natural world, and is due mainly to that 

 increasing exactness of experiment and observation, of 

 which number, weight, and measure are the practical 

 exponents. Savoir pour prevoir is the key to all scien- 

 tific predictions. Every branch of physical knowledge 

 is rich in examples of them. Astronomy, Optics, 

 Chemistry, and Electricity furnish the most striking 

 such as the elliptic polarisation of light the discovery 

 of new metals by spectrum analysis the discovery of 

 Neptune through the perturbations of Uranus the 

 discovery of numerous chemical compounds through 

 the laws of atomicity and definite proportions, &c. 



