XVII. The Bakerian Lecture.— On photographic method of mapping the least refrangible end of the solar spectrum

Abstract

The research which I commenced some five years ago on a method of photography by which the least refrangible end of the solar spectrum could be mapped has reached such a stage that it seems desirable that I should put on record the results I have obtained, and with it to present a map of the solar spectrum between wave lengths 7600 and 10,750 based upon measurements from a series of photographs which appear to be satisfactory for the purpose. Action of dyes on silver bromide . In December, 1873, Dr. H. C. Vogel, of Berlin, announced that by means of dyed collodion films which contained silver bromide he had been enabled to photograph with the yellow and green rays of the solar spectrum, which had hitherto been supposed to be possessed of but little chemical effect. About the same time I had set myself the cask of mapping the ultra-red region of the spectrum, and I was naturally led to examine the method advocated by Dr. H. C. Vogel.