1 62, Mr. cockin’s ^Account of. \ &c. 
After all, this is only to be confidered as conjecture. 
Though it does not want analogy, we have not had it yet 
properly afcertained by experiment : and hence it is not 
without reafon, that Dr. priestley confiders the addi- 
tional rows of colours within the common rainbow ob- 
ferved by Dr. langwith, and thofe of the fpecies of 
image here defcribed, as one of the defiderata of optics. 
