150 Royal Society : — Mr. H. C. Sorby on Analysis of Animal 



11. Normal chlorophyll 1 . 



{Deep Green) j « ~ 2 f ™ H-- A h 6$ . - - 7\— 



12. Ditto, as decompo-^ 



sed by acids, or as ! * * 



* 



found in some leaves, f 1— 2| 2| — Sf 4$ . . . 5fc — 5f . . . 6§ — 7| 8£ . - - £ 

 ( Olive Green) ) 



13. Ditto, as decompo-^ 

 sed by caustic potash, f 



and then by hydro- J * * * * 



chloric acid. j* — f 1^ — If 1| — ^ 4£ — 5£ . . . 9 - - 10- 



(Bed- Green, Neutral J 



5. General Remarks on Absolution Sfc. 



It appears to me that in adopting the undulatory theory of light 

 it greatly simplifies the subject before us if we, to some extent, make 

 use of the phraseology of acoustics. And thus, for example, I shall 

 speak of two absorption-bands that occur, one nearer the red, and 

 the other nearer the blve end of the spectrum, as being relatively 

 lower and higher. In a similar manner, if the addition of some re- 

 agent cause the absorption to increase towards the blue, and decrease 

 towards the red, end, I shall describe it as raising the position of the 

 absorption. We may also make some facts more intelligible by com- 

 paring them with the analogous phenomena of sound, and thus, for 

 instance, may suppose that very narrow absorption-bands indicate 

 that the ultimate particles of the substance will only take up vibra- 

 tions of light of nearly one particular velocity, and that broad ab- 

 sorption-bands show that the particles have a much less definite rate 

 of movement. Analogy would also lead us to infer that, when two 

 spectra differ very decidedly, they must be due to different sub- 

 stances or to the same in a different condition ; whereas, if two 

 spectra agree, they may be the same substance, or two distinct sub- 

 stances whose different actions are made equal by particular circum- 

 stances. As an illustration, we may refer to a short string, which 

 may give the same note as a longer whose tension is greater. For 

 this reason we should be careful not to rely too much on one spec- 

 trum. If, however, we can produce some great physical change in 

 both substances, and still their spectra remain the same under equal 

 conditions, and if this occur uniformly in several different changes, 

 we may conclude that they are identical. Hence the value of the 

 various" reagents named below. Many excellent illustrations of these 

 principles could easily be given. 



6. General Method of Experiments. 



Since the spectrum-microscope enables us to use very small quan- 

 tities, it appeared desirable to adopt such a method of research as 

 would enable us to take full advantage of this circumstance, and to 

 avoid as much as possible previous chemical manipulations. On 

 this account I shall say nothing about modified chemical methods, 

 which may, of course, be also employed when sufficient material is 



