1 88 PROGRESS OF SCIENCE. 



Gladstone, Dr. Carnelley, Clarke and others, have held that 

 our supposed simple elements are really complex, and must 

 have come into existence by the evolutionary development 

 of some primordial matter. But Crookes it was who, for 

 years, investigated the question most elaborately, by his 

 analysis of " rare earths" especially yttria, which he calls 

 his Rosetta Stone present in samarskite, gadolinite, and 

 other minerals,* through the process of chemical fractioni- 

 sation. To settle a single point regarding the nature of 

 yttria he performed upwards of two thousand fractionisations ! 

 He does not claim to have demonstrated or established 

 chemical evolution, but he thinks that the balance of evi- 

 dence fairly weighs in favour of it. If evolution be a cosmic 

 law which enables us to account for the origin and formation 

 of heavenly bodies according to Laplace, of the earth according 

 to Lyell, of plants and animals according to Lamarck, Darwin, 

 and Wallace, then it is difficult to believe that it does not 

 hold good in chemistry development of matter as well. 

 All our knowledge tends more and more to force the con- 

 viction upon us that unity of energy governs the Cosmos, 

 and that principle almost necessarily involves unity of matter 

 as it involves unity of law. Whether one day this be 

 demonstrated, or whether the contrary be established, 

 Crookes will, in either case, always be considered as one 

 of the keenest pioneers of a wonderful age, and one who 

 forwarded in no small degree the settlement of the deepest 

 questions of scientific philosophy. We shall further on see 

 the services which he has rendered to physics. 



b. 1837. Perkin (William Henry) discovered (1856) 

 the first of the ANILINE DYES the source of an immense 

 increase of trade and wealth throughout the world ; made 

 a great number of discoveries in organic chemistry, and 

 greatly distinguished himself by applying the measurement 

 of the MAGNETIC ROTATION OF ORGANIC SUBSTANCES to 

 the study of their constitution. 



18 . Mendelejeff formulated the PERIODIC LAW, 



* To obtain almost pure yttria cost Crookes fifteen months' work, and 

 another ten months to eliminate from it the aWinnrth part of impurity it 

 contained. 



