viii PKEFACE . 



One of the advantages which has come from the introduc- 

 tion of new apparatus has been the possibility of making maps 

 of the solar lines and of the metallic lines which have to be 

 compared with them on a very large scale. Thanks to the 

 generosity of Mr. Rutherfurd and the skill of Professor 

 Rowland, magnificent diffraction-gratings have been spread 

 broadcast among workers in science, and we have therefore 

 easy means of obtaining with inexpensive apparatus a spectrum 

 of the sun, and of mapping it on such a scale that the fine line 

 of light which is allowed to come through the slit is drawn 

 out into a band or spectrum half a furlong long. A complete 

 spectrum on this scale, when complete (as I hope it some day 

 will be, though certainly not in our time), from the ultra- 

 violet to the ultra-red, will be 315 feet long, on the scale on 

 which I have already been working. This is a considerable 

 scale to apply to the investigation of these problems ; but recent 

 work has shown that, gigantic as the scale is, it is really not 

 beyond what is required for honest, patient work. 



I announced some years ago to the Royal Society that, 

 reasoning from the phenomena presented to us in the spectro- 

 scope when known compounds are decomposed, I had obtained 

 strong evidence that the so-called elementary bodies are in 

 reality compound ones. 



The idea of simplifying the elements is connected with the 

 philosopher's stone ; the use oFthe philosopher's stone was to 

 transmute metals ; therefore I was at first supposed to be 

 " transmuting " metals ; and imaginations had been so active 

 in this direction that I am not sure that when one of my 



