52 Notes upon some Atmospherical PJienomena [No. 1. 



As before remarked, the two phenomena just described were seen 

 between the spectator and the sun, the spectator having his face 

 turned towards the sun, and that they owed their brilliant prismatic 

 colours to light refracted by small spiculae of ice floating in the at- 

 mosphere ; those now about to be described, on the contrary, were 

 seen when the spectator was between the sun and the phenomena ; 

 and with the back turned towards the sun ; and further they owe 

 their prismatic colours to the refraction of light, falling upon minute 

 vesicles of water containing air suspended in fogs ; they are in fact 

 Fog-lows and all those seen by me were seen early in the morning 

 when the sun was 12° to 18° above the horizon. 



The spectator must be placed between the sun and a fog ; turning 

 his face towards the fog he will see his figure reflected upon the oppo- 

 site cloud, surrounded by a succession of concentric circles of brilliant 

 colours, refracted by the watery particles of the fog ; and following 

 the order of the colours as seen in the rainbow. (Vide Plate III.) 



A line drawn from the sun through the spectator's head to the 

 common centre of the circles is a straight line. 



The general appearance of a very perfect fog-bow, is as follows ; 

 by which it will be seen, that some of the colours of the prism are 

 wanting, or taking violet or the upper colour of the solar spectrum 

 as 1, numbers, 2, 3, 4 and 6, are wanting. The spectator sees his 

 figure about thirty yards in front of him, surrounded by a disc of a 

 greyish, or pinkish neutral tint, with a diameter equal to his own 

 height, but with the head exactly in the centre ; beyond this central 

 disc which is edged on the outer circle with a pale violet, appear the 

 following circles of colour, viz. violet, yellow, orange, their width 

 bearing the correct proportion as ascertained by the prism, viz. the 

 violet eighty parts ; yellow forty ; orange twenty-seven ; the three 

 circles occupy three semi-diameters of the central disc ; beyond this 

 first series of circles another series is visible, observing the following 

 arrangement of colours ; violet, green, yellow, orange ; the circles 

 being much broader than those in the first series, the brilliancy of 

 their colours much fainter and rather confused. Beyond this second 

 series of colours a colourless or white bow is sometimes seen with 

 a radius equal to six semi-diameters of the inner or first series of 

 colours, viz. from the centre of the disc where the spectator's head 

 is reflected, to the exterior of the first orange colour. 



