1867.] 



Colouring -matters by the Spectrum Microscope. 



437 



account of this system, I here give a printed illustration, which will show 

 that by this means it is easy to give in a single line all the essential parti- 

 culars which would otherwise require a long and tedious description, or a 

 number of drawings and woodcuts. Without some such method of measu- 

 ring and recording spectra it would be almost impossible to carry on 

 extensive inquiries. 



The intensity of the absorption is expressed by the following types : — ■ 



Not at all shaded Blank space. 



Very slightly shaded . . . Dots with wide spaces. 



Decidedly shaded . . . Dots closer together. 



More shaded ... Very close dots. 



Strongly shaded, but so that a trace \ _ _ hvnhens close 



of colour is still seen / iiypHens close. 



Still darker — Single dash. 



Nearly black Double dash. 



Except when specially requisite, only the symbols ... — — are em- 

 ployed for the sake of simplicity, and then as signs of the relative, rather 

 than of the absolute, amount of absorption ; and it is assumed that there 

 is a gradual shading off from one tint to the other, unless the contrary is 

 expressed. This is done by means of a small vertical line over the figure 

 (see No. 1 1 ), which shows that there is a well-marked division between 

 them. Definite narrow absorption-bands are indicated by * printed over 

 their centre. This will be better understood by a description of the spec- 

 trum of deoxidized hsematin. 



M Z ^ % 



W ^ Cb ^ III 



4| — 5 5i 6| 9 . . 10 — 11 — 



The following examples will show how simple or more complicated 

 spectra may thus readily be printed and compared. I have chosen solu- 

 tions of similar tint, in order to show that the spectra of those of nearly 

 the same colour may be very different, or, if analogous, may differ in 

 details easily expressed by the symbols. The colour of each is given after 

 the name. Nos. 1, 8, 9, 10, 11, 12, and 13 can be kept for a long time 

 sealed up in tubes, and the rest are easily prepared. I have in all cases 

 chosen that strength of solution which gives either the most characteristic 

 spectra, or those best suited for comparison with other allied colours. 



1. Cudbear in alum (Pink) 3 8 11 . — 



2. Colour of Elder berries with \ 



citric acid. (Red Pink) J 



4 . - 5^—8 - - 9 ... 11 



Brazil-wood, with bicarbonate 1 * 



of ammonia. (Pink) j 4^ — 5f J 



Logwood, with bicarbonate of! * 



ammonia. (Pink) j 3| — 5^ 7 



