270 Harttey—The Action of Heat on the Absorption Spectra and 
very questionable whether any value can be attached to measurements carried 
beyond three figures, unless perhaps in the bands of didymium salts, which are 
strong and well defined. 
Hence the measurements of the cobalt spectra are recorded to three figures 
only. Absorption bands which are diffuse cannot be accurately measured with 
great dispersion. 
The Spectra of Cobalt Salts. 
CoCl,6H,0.—A saturated Aqueous Solution at 20° ©. 
Thin wedge cell, measurements taken at the middle of the cell. Photograph 
No. 1 :— nN 
Spectrum begins at . 6 : ; 6 : ; 656 
Rays transmitted from 656 to . . ‘ : : 572 
Absorption Band. : : : : ; . 572 to 474 
Rays transmitted from 474 to . 5 : 5 342 
End of spectrum. 
At the upper part of the cell :— 
Spectrum begins at . : : : : : : 649 
Rays transmitted from 649 to . : . : : 612 
Absorption Band. : : : : : . 612 to 443 
Rays transmitted from 443 to . : : : : 372 
End of spectrum. 
CoCl,'6H,0.—Saturated Aqueous Solution at 20° C. 
Measurements taken at the middle of the cell. Photograph No. 2 :— 
r 
Complete absorption up to where spectrum begins. 653 
Absorption Band. : . 653 to 642 
Absorption Band, with stpondest side towards r 627, . 642 to 627 
Absorption Band, with its strongest side at 612, . 627 to 612 
Rays transmitted strongly to. ; : : : 584 
Great Absorption Band. : : ; : . 580 to 450 
Rays transmitted from 450 to . ; : ; : 347 
Measurements taken at the upper part of the cell :— 
Rays feebly transmitted from . : : : : 627 
Spectrum extends to. : : : : : . 620 
Absorption Band. : : : : . 620 to 612 
Rays transmitted from A 612 i 9 : 602 
Indications of an absorption band with its obits a 608 
Absorption Band. : : : ‘ : . 601 to 597 
Rays feebly transmitted to 6 3 : 6 6 589 
Great Absorption Band. : : ‘ 5 . 589 to 436 
Rays transmitted from » 436 to 6 6 6 . 356 
