438 Mr. H. C. Sorby on Analysis of Animal and Vegetable [Apr. 11, 



The next four are spectra of blood, produced by the successive addition 

 of the various reagents, as in detecting fresh stains. 



5. Fresh Blood. {Pale Scarlet) 3^ — 4f , 4| — 5| 7 . . 8 - - 9— 



6. Citric Acid then added. T * 



{Fale Brown) j If ... 2^ 4 ... 8 ... 9 — 10 — 



7. Ammonia then added. 1 * * 



{Pale Brown) J 3f . . . 4| 4| . . . 5f 7 . . 8 — 10— 



8. Deoxidized hsematin, from blood- \ * * 



stain 2 years old. {Pink) J 4^ — 5 5^ . . . 6f 9 . . 10 — 11 — 



With these may be compared the two spectra which more nearly resemble 

 those produced by blood than any I have yet seen. 



9. Cochineal in alum. {Pink) of — 4^ . . . 5^ — 6^ . . . 7^ 



10. Alkanet-root in alum. {Pink) 3^ — 4f 5^ . . . 5| 



The following spectra of compounds derived from chlorophyll are as 

 complicated as any I have met with. 



11. Normal chlorophyll 

 in alcohol. 



{Beep Green) J 



12. Ditto, as decompos- 



ed by acids, or as ! * * * * 



found in some leaves. [ 1— 2^ 2| ™ 3f 4^ . . . 5^ — 5f . . . 6f — 7| 8^ . - - 9^- 



{Olive Green) ) 



13. Ditto, as decompos- ^ 

 ed by caustic potash, 



and then by hydro- ! * * * * 



chloric acid. f i — I H — If 1| — 2^ 4^ — 5|- ... 9 - - 10- 



1 * 



r -I — 2^ — 



21-3^.... 4^ 6i.--7h 



{Eed^ Green, Neutral 

 Tint) J 



5. General Hemarks on Absorption, ^c. 



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 

 blue, end of the spectrum, as being relatively lower and higher. In a 

 similar manner, if the addition of some reagent cause the absorption to in- 

 crease 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 comparing 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 vibrations of light of nearly one particular velocity, and that broad 

 absorption-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 vi^ry decidedly, they must be due to different substances, or to the 



