594 BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 



Herschel, W.: Synopsis of the Writings of— Continued. 



A. B. Tol. P. 



Id09 99 2G1-282 XXXVII. Irregular Curves produce irregular Figures. 



XXXVIII. Curved Surfaces are required for producing the coloured Ap- 

 pearances at present under consideration. 

 203 XXXIX. Coloured Ajjpearanccs cannot he produced between the plain Sur- 

 faces of two parallel Pieces of Glass applied to one another. 

 This conclusion is derived from the observation that colours appear 

 between two such glasses only when they are pressed together with 

 considerable force ; but such pressure necessarily produces distorticn 

 of form in the glasses. 

 264-265 XL. Of the Production of coloured Appearances. 

 265 The colours contained in white light may be separated by reflection, 

 as well as by refraction. The production of the blue bow at the 

 limit of total reflection, as described by Sir Isaac Newton, is an 

 instance of this effect. 

 266-268 XLI. Particulars relating to the Newtonian prismatic blue Bow. 



A description of the phenomenon, with a calculation of its place and 

 breadth in a particular case. 

 268-272 XLII. Account of a prismatic red Boiv. 



268 This consists of red, orange, yellow, and some green rays, the red 



colour being very predominant. To see the red bow, an observer 

 should place himself in the open air, and, standing with his back 

 within a few feet of some wall or building, hold the sides of an 

 equilateral jirism flat over his eyes, and look upwards to an altitude 

 of about 30° at the heavens. 



269 Calculations relating to this bow. 

 270-271 Method of projecting the bow. 



272-274 XLIII. Of a sudden Change of the Colours of the Bows. 



272 If a right-angled prism be laid down on a sheet of white paper before 



a window, and the eye be placed in the proper position for seeing 

 the blue bow, we may instantly transform it into red one by cover- 

 ing the side of the prism which is toward the incident light with a 

 slip of pasteboard. 



273 Relative positions of red and blue bows. 



274-276 XLIV. Of Streaks and other Phenomena produced from the prismatic 

 blue and red Bows. 

 These may be jiroduced by applying a surface of glass or metal to 

 that surface of the prism which produces the one or the other bow. 

 276-279 XLV. Explanation of various Appearances relating to prismatic Boivs. 

 280-281 XLVI. The first Surface of a Prism is not concerned in the Formation 

 of the blue Bow, nor of the Streaks that are produced by a plain 

 Glass applied to the efficient Surface. 

 281-284 XL VII. Tlie Streaks which may be seen in the blue Boui contain the 

 colours of both the Parts of the prismatic Spectrum, by the critical 

 separation of xchich the Bow is formed. 

 282 List of colours observed in streaks. 

 284-291 XLVIII. On the Formation of Streaks. 



This is an efl'ort to determine by calculation some of the features of 

 the phenomenon under the supposition that the streaks are pro- 

 duced by a reflection, at the surface of the glass plate, of the light 

 transmitted by the prism near the critical angle. 

 291-292 XLIX. Prismatic Boies, ichen seen at a Distance, are straight Lines. 

 292-294 L. The colours of the Bow-streaks owe their Production to the Principle 

 of the critical Separation of the different Parts of theprismatic Spectrum. 



