442 Mr. W. Hardie's Description of a New Pseudoscope. 



from those who have seen it under the most favourable circum- 

 stances, that its brightness much exceeded that of the secondary, 

 and more nearly equalled that of the primary rainbow. Under 

 very favourable circumstances, therefore, a secondary horizontal 

 iris might be seen more frequently than a tertiary rainbow ; and 

 cases might be conceived, as not beyond the possibility of occur- 

 rence, in which the secondary horizontal iris should be visible, 

 while from the causes above alluded to, the primary could not 

 be seen. I have never myself seen this secondary bow, nor have 

 I met with any one who had. 



One illustration of the popular error prevalent with respect to 

 the ' horizontal iris ' may be alluded to. It is not uncommon in 

 some of those sketches of scenery under the effect of shower and 

 sunshine, which our artists love so well, to observe a very pal- 

 pable attempt at painting in a calm sheet of water, occupying 

 the foreground or middle distance, a reflexion of part of an arch 

 of the rainbow ; the attempt being made evident by the exercise 

 of those artifices by which painters throw images formed by 

 reflexion in water, beneath its surface. 



Kingstown near Dublin, 

 April 26, 1863. 



P.S. It may seem almost affectation to observe, in reference 

 to a paper so unpretending as the above, that it was not sug- 

 gested by Mr. Pratt's paper which appeared in the Philosophical 

 Magazine for February ; having, in fact, been written previously 

 to the writer having seen that article. The two papers obviously 

 have no further connexion than the circumstance of both refer- 

 ring to phsenomena occasionally accompanying rainbows. 



LXX. Description of a New Pseudoscope. 



By Walter Hardie, Edinburgh. 



[With a Plate.] 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



PERHAPS the following description of a new pseudoscope 

 may interest those of your readers who have studied Pro- 

 fessor Wheatstone's and Sir David Brewster's papers upon bino- 

 cular vision. It consists of a simple combination of plane reflect- 

 ors, and may be constructed of pieces of thin looking-glass. In 

 the accompanying diagrams these are represented in section by 

 the thick black lines ; the thin lines, representing the visual rays 

 as reflected by the mirrors, will also serve to indicate the position 

 of the reflecting surfaces. The peculiar properties of this instru- 

 ment are, — 



