166 Mr. J. N. Lockyer. Researches in Spectrum [Dec. 12 r 



of the basic lines actually observed, tlie inquiry seemed worthy of 

 being carried to a farther stage. 



The next point I considered was to obtain a clear mental view of 

 the manner in which, on the principle of evolntion, varions bases might 

 now be formed, and then become basic themselves. 



It did not seem unnatural that the -bases should increase their com- 

 plexity by a process of continual multiplication, the factor being 1, 2, 

 or even 3, if conditions were available under which the temperature of 

 their environment should decrease, as we imagined it to do from the 

 furnace A down to furnace D. This would bring about a condition 

 of molecular complexity in which the proportion of the molecular 

 weight of a substance so produced in a combination with another sub- 

 stance would go on continually increasing. 



Another method of increasing molecular complexity would be repre- 

 sented by the addition of molecules of different origins. Representing 

 the first method by A + A, we could represent the second by A + B. 

 A variation of the last process would consist in a still further com- 

 plexity being brought about by the addition of another molecule of B, 

 so that instead of (A-f B) 2 merely, we should have A-f B 2 . 



Of these three processes the first one seemed that which it was pos- 

 sible to attack under the best conditions, because the consideration of 

 impurities was eliminated ; the prior work has left no doubt upon the 

 mind about such and such lines being due to calcinm, others to iron, 

 and so forth. That is to say, they are visible in the spectra of these 

 substances as a rule. The inquiry took this form : Granting that these 

 lines are special to such and such a substance, does each become basic 

 in turn as the temperature is changed ? 



I therefore began the search by reviewing the evidence concerning 

 calcium, and seeing if hydrogen, iron, and lithium behaved in the same 

 way. 



Application of the above Calcium Views to Calcium, Iron, Lithium, and 



Hydrogen . 



Calcium. 



It was in a communication to the Royal Society made in 1874 

 (" Proc. Roy. Soc," vol. xxii, p. 380), that I first referred to the 

 possibility that the well-known line spectra of the elementary bodies 

 might not result from the vibration of similar molecules. I was led to 

 make the remark in consequence of the differences to which I have 

 already drawn attention in the spectra of certain elements as observed 

 in the spectrum of the sun and in those obtained with the ordinary 

 instrumental appliances. 



Later (" Proc. Roy. Soc," No. 168, 1876) I produced evidence that 

 the molecular grouping of calcium which, with a small induction coil 

 and small jar, gives a spectrum with its chief line in the blue, is nearly 



