INDEPENDENCE OF TITHONIC RAYS AND HEAT. 



161 



its corresponding tithonograph. This spectrum is divided into three portions, one of 

 which is red and yellow, a second indigo, and a third violet. But the tithonograph ex- 

 hibits an action far heyond the extreme red, half way through the dark space that in- 

 tervenes in the middle of the spectrum, both ends of this lower part projecting into 

 dark spaces ; while the indigo ray, ordinarily so active, does not tithonize at all. 



66G. Without going into a long descriptive detail of the comparison of different 

 spectra and their corresponding tithonographs, I shall here sum up the results which 

 may he gathered from an inspection of the plate. 



667. By the absorbent action of the persulphocyanide of iron, we can prove the ex- 

 istence of invisible tithonic rays beyond the extreme red invisible rays corresponding 

 to the green. We can also prove that the indigo-coloured rays of LIGHT may exist 

 without tithonic effect. 



668. By the absorbent action of neutral chloride of gold, we can insulate blue-col-* 

 cured rays of light that are not tithonic. 



669. The green solution formed by a mixture of bichromate of potash, muriatic acid, 

 and alcohol, enables us to insulate tithonic rays of the same refrangibility as the violet, 

 but unaccompanied by any light. 



670. The solution of sulphate of copper and ammonia enables us to insulate a visible 

 red and yellow ray that are without tithonic power, and an invisible tithonic ray beyond 

 the violet. 



671. The solution of litmus enables us to obtain red and green light without action, 

 and an invisible tithonic ray corresponding to the violet. 



672. The solution of bichromate of potash enables us to obtain red and orange light 

 without any tithonic effect. 



673. Such results might be multiplied without end, for, indeed, there is scarcely 

 an instance in which spectra of rays that have passed absorbent media are exactly 

 coincident with their corresponding tithonographs. To set the matter plainly before 

 the reader, the following tabular view, gathered from the plate, may suffice : 



From this, therefore, I infer the entire independence throughout the spectrum of the 

 luminous rays that give to the organs of vision the impression of colour and the tithonic 

 rays. 



674. When I come to describe the dark tithonic rays that are analogous to the rays 

 of dark heat, and which are unaccompanied by any kind of light whatsoever, no farther 

 doubt can be entertained on this subject. I have also some other proofs of a very 

 remarkable kind, to be described hereafter, drawn from the phenomena exhibited by 

 tithonic rays that have undergone polarization. 



675. Next, as to the independence of these rays and the rays of heat. 



X 



