APPENDIX. IL 479 



^reighteof all the elements, And once again the inductive or experimental 

 method of studying Nature gained a direct advantage from the old Pytha- 

 gorean 'ide'a : because atomic weights were determined with an accuracy 

 formerly unknown. But again the idea could not stand the ordeal of expert- 

 tnental test, yet the prejudice remains and has not been uprooted, even by 

 'Stas; nay, it has gained a new vigour, for we see that all which is imperfectly 

 worked out, new and unexplained, from the still scarcely studied rare metals 

 to the hardly perceptible nebulae, have been used to justify it. As soon da 

 spectrum analysis appears as a new and powerful weapon of chemistry, the 

 idea of a primary matter is immediately attached to it. From all sides we 

 see 'attempts to constitute -the imaginary substance helium, 9 the, so much 

 longed for primary matter.. No attention is paid to the circumstance that 

 the helium line is only seen in the spectrum of the solar protuberances, so 

 that its universality in Nature remains, as problematic as the primary matter 

 itself ; nor to the fact that the helium line is wanting amongst the Fraun- 

 hofer lines of the solar spectrum, and thus does not answer to the brilliant 

 fundamental conception which gives its real force to spectrum analysis. 



And finally, no notice is even taken of the indubitable fact that the bril- 

 liancies of the spectral lines of the simple substances vary under different tem- 

 peratures and pressures ; so that all probabilities are in favour of the helium 

 line simply belonging to some long since known, element placed under such 

 conditions of temperature, pressure, and gravity as have not yet been realised 

 in our experiments. Again, the idea that the excellent investigations of 

 Lockyer of the spectrum o iron can be interpreted in favour of the compound 

 nature of that element, evidently, must have arisen from some misunder- 

 standing. The spectrum of a compound certainly does not appear as a 

 sum of the spectra of its components ; and therefore the observations of 

 Lockyer can oe considered precisely as a- proof that iron undergoes no other 

 changes at the temperature of the sun than those which it experiences in the 

 voltaic arc provided the spectrum of iron is preserved. As to the shifting 

 of some of the lines -of the spectrum of iron while the other lines maintain 

 their positions, it can be explained, as shown by M. Klelbetf ('Journal -of the 

 Russian Chemical and Physical Society, 1885, 14*7), by the relative motion 

 of the various strata of the sun's atmosphere, and by Zollner's laws of the 

 relative brilliancies of different lines of the spectrum. Moreover, it ought 

 not to be forgotten that if iron were really proved to consist of two or more, 

 unknown elements, we should simply have an increase in the number of our 

 elements^-not a reduction, and still less a reduction of all of them to one 

 single primary matter. 



Feeling that spectrum analysis will not yield a support to the Pythagorean 

 conception, its. modern promoters are so bent upon its being confirmed by 

 the periodic law, that the illustrious Berthelot, in his work * Les origines de 

 i'Alchjmie,' 1885, 318, has simply mixed up the fundamental idea of the law 

 of periodicity with the ideas of Prout, the alchemists, and Democritus about 

 primary matter, 4 But the periodic law, based as it is on the solid and whole- 



8 That is, a substance having a wave-length equal to 0*0005875 millimetre, 

 * He maintains (on p. 800) that the periodic law requires two new analogous 

 elements, having atomic Weights of. 48 and 64, occupying positions between sulphur 



