Reflection of Light. 39 



Once now and then, looking at this range of hills 

 from a distance of two or three miles on moonless 

 nights, wlien it has been sufficiently clear to distin- 

 guish them, I have noticed that the particular down 

 on which the earthwork is situate shows more dis- 

 tinctl}^ than the others. By da}' no difference is ap- 

 parent ; but sometimes by night it seems slightly 

 lighter in hue, and stands out more plainly. This 

 may perhaps be due to some unobserved character- 

 istic of the herbage on its slope, or possiblj^ to the 

 chalky subsoil coming there nearer to the surface. 

 The power of reflecting light possessed by the earth, 

 and varied hy different soils or by vegetation, is worth 

 observation. 



