VI. 0« the Dhi^rslo,, of LigU_ m e^pUmd by the Hmthem ct 



[Read Feb. 22, 1836.] 

 PRELIMINARY OBSERVATIONS. 



There is no phenomenon in Optics more familiar and prominent 

 than that a beam of solar light is composed of differently coloured rays 

 each endued with its own peculiar properties. ' 



It was first satisfactorily proved by Newton, that the parts are dis 

 tinct from each other, and are susceptible of separation and recompo- 

 sition, so that any particular colour can be examined apart from the 

 rest. At a very recent period Wollaston and Fraunhofer have examined 

 more mtimately the constitution of a beam of ordinary white light 

 and from the accurate measures of the latter, we are put in possesion 

 of a series of data by which, in a variety of substances, the position 

 of each particular portion of the beam is accurately defined. Having 

 then before us such observations, we are in a state to proceed to an 

 explanation not merely of facts broadly and generally stated, but of 

 the minutest detads, and most trivial deviations from the rough outhne. 



It might perhaps be more easy to proceed on the hypothesis which 

 Newton himself advanced, as it would be a matter of little difficulty 

 to assign such forces or inertia to the particles of light, combined with 

 the constant attractive or repulsive forces of the material particles com 

 Vol. VI. Part I. u 



