at the Surface of Highly-absorbing Media. 355 



transparent medium. If a film of fuchsine is situated between 

 air and glass we should therefore expect to find a displacement 

 of the interference-bands. 



Change of Phase on Reflexion. 



Glass-fucbsine (§ 5). — An increasing acceleration as we go 

 from the violet to the red end of the spectrum = 

 approx. at the violet end and approx. ir at the 

 red end. 



Air- fuchsine (§ 6) . — A retardation reaching a maximum in the 

 green and falling off to approx. it at either end 

 of the spectrum. 



Fuchsine-glass (§ 4). — Assume = glass-fuchsine +tt. 



Fuchsine-air (§4). — Assume = air-fuchsine ±7r. 



Table B, 1st Column. 



Towards the violet end of the spectrum the light reflected 

 dye-glass is abnormally retarded relatively to that reflected 

 air-dye. That is to say, the light coming from the second 

 surface is abnormally retarded relatively to that coining from 

 the first. This causes the maxima and minima when the film 

 is viewed directly to be displaced towards the thin end of the 

 film, § 3. 



Table B, 2nd Column. 



Towards the violet end of the spectrum the light reflected 

 dye-air is abnormally accelerated relatively to that reflected 

 glass-dye. That is to say, the light coming from the second 

 surface is abnormally accelerated relatively to that coming 

 from the first. This causes the maxima and minima when the 

 film is viewed through the glass to be displaced towards the 

 thick end of the film, the displacement being greatest towards 

 the violet end of the spectrum. 



Thin films of acid green, and of methyl aniline violet, show 

 a concordant displacement of interference-bands. 



As it is impossible to regulate the gradient of thickness in 

 these thin films, no attempt has been made at accurate 

 measurement. 



