C. C. Hutchins — Irregular Reflection. 377 



by Arthur Searle* from the analytical study of the reflection 

 of a furrowed cylinder. Other bodies of greater or less fine- 

 ness of grain or powder illustrate the same fact. A few are 

 here given. 





Clay 

 Gal. 



Red. 



Marble powd. 

 Gal. Red. 



Lava. 

 Gal. Red. 



10° 



100 



98-5 



130 



98'5 



94-2 



98-5 



20 



86-5 



85-0 ■ 



124 



93-6 



83*5 



87-3 



30 



80*5 



79-1 



107 



8T4 



69*3 



72-4 



40 



75-2 



73-9 



94-3 



71-4 



63-6 



66-5 



50 



58'5 



57-5 



76-5 



58*0 



53-6 



56-0 



60 



45-7 



44-9 



62-5 



47*4 



43-6 



45-6 



70 



30-8 



28*2 



39-0 



296 



28-3 



29-6 



80 



16-0 



157 



17-5 



13*3 



16*4 



17'1 



The inference to be derived from these observations seems 

 to be that the manner of reflection of any body is to be learned 

 only from an experimental study of it. 



Sext after a plane the sphere is perhaps the surface possess- 

 ing the most interest ; a knowledge of its manner of reflection 

 being of special importance in astronomy in problems relating 

 to the light given by the planets and other bodies. 



Lambert's formula for the reflection of a smooth sphere is 

 L = 1 /tz (sin v — u cos v). The curve of this equation is rep- 

 resented in fig. 5, by the smooth continuous line. The phase 

 angle at new moon is taken as 0° and the light at apposition 

 equal to 100. 



Phase angle. Magnesia. Lead. Red clay. Moon. 



4-24 12*6 



7-46 18-2 



13-3 26-7 



19-9 

 25-9 34-0 25-0 



31-0 

 43-8 40-6 37-5 



44-9 

 66*4 610 53-6 



62-8 

 85-2 72-8 73-2 



83-9 

 98*5 92*1 93-8 



180 100 100 100 100 



Substituting now for the flat surface a small carefully pre- 

 pared sphere of magnesia obtained by smoking an ivory ball 



* Phases of the Moon, American Academy of Arts and Sciences, 1884. 



30° 



3-00 



40 



4-71 



50 



7-52 



60 



11-5 



70 



17-0 



80 



23-3 



90 



31*1 



100 



39-1 



110 



51-3 



120 



58-9 



130 



69'4 



140 



79*3 



150 



88-0 



160 



93-5 



170 



98-4 



