PRESIDENTIAL ADDRESS, B.A. 1871. 175 



To the prodigious and wearing toil of Kirchhoff 

 himself, and of Angstrom, W c owe large-scale 



o o 



maps of the solar spectrum, incomparably superior 

 in minuteness and accuracy of delineation to any- 

 thing ever attempted previously. These maps now 

 constitute the standards of reference for all workers 

 in the field. Pliicker and Hittorf opened ground 

 in advancing the physics of spectrum analysis and 

 made the important discovery of changes in the 

 spectra of ignited gases produced by changes in 

 the physical condition of the gas. The scientific 

 value of the meetings of the British Association is 

 well illustrated by the fact that it was through 

 conversation with Pliicker at the Newcastle meet- 

 ing that Lockyer was first led into the investigation 

 of the effects of varied pressure on the quality of 

 the light emitted by glowing gas which he and 

 Frankland have prosecuted with such admirable 

 success. Scientific wealth tends to accumulation 

 according to the law of compound interest. Every 

 addition to knowledge of properties of matter 

 supplies the naturalist with new instrumental 

 means for discovering and interpreting phenomena 



