390 



PROCEEDINGS OP THE AMERICAN ACADEMY 



TABLE L 



second gives the observed amount of light transmitted, the third gives 



the amount transmitted as calculated by the formula t = t— r— --, 



•' ! + ('« — i)^i 



in which A is the amount reflected from one surface, and m the num- 

 ber of surfaces. The quantity A was determined by solving the equa- 

 tion t = ■ . ^. , in which t was carefully determined by a considerable 



number of observations. The fourth column gives the differences 

 between the observed and computed values, which are within the 

 limits of errors of observation. It will thus be seen that these obser- 

 vations give a very accurate proof of the above formula. 



TABLE II. 



