u 



It may be necessary to give some explanation of the Frontispiece, lest 

 the reader impute to it a mystic, symbolical character, other than it is 

 intended to convey. 



No. 1 represents the Spectrum produced by the Newtonian Prism 

 with the prismatic Colours, and the emblematical representation of the 

 Magnetic forces. 



No. 2 exhibits the appearance of the Aureola, obtained bv the action 

 of the Lenticular Prism of Field, on a black spot, on the white 

 ground. 



No. 3 is the Aureola from a white spot, on a dark or black ground, 

 by the same instrument ; for the explanation of the back-ground of the 

 lower Diagram, the reader is referred to the first ten verses of the 1st 

 Chapter of Genesis, and subsequently to ch. ixi v. 13. 



ERRATA. 



Page 63, for "Del CementO," read " The Del Cemento" being a 

 Scientific Association. 



Page 65, heading, for "NOT reflexible," read " MOST reflexible." 

 The note in page 115 ought to have been placed in page 56. 



103247 



