THE UNDULATORY THEORY. 491 



gungs-erscheinungen, (Phenomena of Inflection,) 

 1836. In this Treatise, the author has with great 

 industry and skill calculated the integrals which, as 

 we have seen, are requisite in order to trace the 

 consequences of the theory; and the accordance 

 which he finds between these and the varied and 

 brilliant results of observation is throughout exact. 

 "I shall," says he, in the preface 18 , "prove by the 

 present Treatise, that all inflection -phenomena, 

 through openings of any form, size, and arrange- 

 ment, are not only explained by the undulation- 

 theory, but that they can be represented by analy- 

 tical expressions, determining the intensity of the 

 light in any point whatever." And he justly adds, 

 that the undulation-theory accounts for the pheno- 

 mena of light, as completely as the theory of gravi- 

 tation does for the facts of the solar system. 



9. Objections to the Theory. We have hitherto 

 mentioned only cases in which the undulatory 

 theory was either entirely successful in explaining 

 the facts, or at least hypothetically consistent with 

 them and with itself. But other objections were 

 started, and some difficulties were long considered 

 as very embarrassing. Objections were made to 

 the theory by some English experimenters, as Mr. 

 Potter, Mr. Barton, and others. These appeared in 

 scientific journals, and were afterwards answered in 

 similar publications. The objections depended partly 

 on the measure of the intensity of light in the dif- 

 11 Dated Speyer, Aug. 1835. 



