ON LIGHT. 399 



passing from red to green, but with increasing and finally 

 with extreme rapidity in the passage thence to violet. 



(174.) It is time, however, to bring this long Lecture to 

 a conclusion. To describe the variety of splendid and 

 singular phaenomena, developed in every department of 

 physical enquiry by the use of polarized light, not one 

 of which has hitherto afforded any, the smallest, ground 

 for doubt as to the applicability of the undulatory theory 

 to its complete explanation, would require volumes. We 

 would gladly have said something of the magnificent 

 phaenomena, exhibited by "macled" crystals,* and by 

 unannealed, or compressed glass ; of the changes pro- 

 duced by change of temperature on the optical relations 

 of bodies, and of the calorific and chemical rays of the 

 spectrum; but our limits forbid it. Suffice it to add, 

 that what the telescope and the microscope effect for us 

 in the discovery of outward and visible form, the proper- 

 ties of light, and especially of polarized light, effect in 

 subjecting to our intellectual vision the intimate structure 

 of material bodies. Within the compass of the smallest 

 visible atom they open out a world of wonders a uni- 

 verse sui generis, and for each atom of a different material 

 a different one all, however, related and bound together 

 in one vast harmony. 



* These may find a place elsewhere. The phenomena alluded 

 to have not, so far as I am aware, been hitherto described. 



