176 POPULAR I.RCTURKS AND ADDRESSES. 



of nature, which in their turn afford foundations 

 for fresh generalisations, bringing gains of perman- 

 ent value into the great storehouse of philosophy. 

 Thus Frankland, led, from observing the want of 

 brightness of a candle burning in a tent on the 

 summit of Mont Blanc, to scrutinise Davy's theory 

 of flame, discovered that brightness without incan- 

 descent solid particles is given to a purely gaseous 

 flame by augmented pressure, and that a dense 

 ignited gas gives a spectrum comparable with that 

 of the light from an incandescent solid or liquid. 

 Lockyer joined him ; and the two found that every 

 incandescent substance gives a continuous spec- 

 trum that an incandescent gas under varied 

 pressure gives bright bars across the continuous 

 spectrum, some of which, from the sharp, hard and 

 fast lines observed where the gas is in a state of 

 extreme attenuation, broaden out on each side into 

 nebulous bands as the density is increased, and arc 

 ultimately lost in the continuous spectrum when 

 the condensation is pushed on till the gas becomes 

 a fluid no longer to be called gaseous. More 

 recently they have examined the influence of tcm- 



