PATTERNS CONSPICUOUS IN NATURE. 



391 



As a circle is the most concentrated form that an object can 

 have, therefore it is the most visible form. The ratio cir- 

 cumference over area only gives the concentration for simple 

 figures. Objects can be made of the same area and of the 

 same circumference but of different concentration. In these 

 cases concentration must be represented by the moment of area 

 round the centre of area. 



Text-fis:ure 5. 



1. ^.3.U 



Vo\xT figures of the same area and of the same circumference but which are not 

 equally visible. The coucentration of their areas is estimated by the length of 

 the cord joining the centre of area of the two triangles. 



EXPBBIMENX No. 6. 



Candles 1 ft. apart. Objects distant from candles 2 ft. 1 in. 



Objects of black needle-paper, of the same area and having the same circumference, 

 composed of two triangles as shown in the figure ; the longest side measured 

 I'l cm., the shortest '5 cm., and the angle opposite the longest side was a right 

 angle. Background of white paper. 



Distance 

 Object. at which visible. 



No. 1 51 feet. 



„ 2 50 „ 



„ 3 47 „ 



» 4 4o-5 „ 



(Mean of six observations.) 



The figure shows the lengths of the cords joining the centres of areas of the two 

 triangles; it can be seen that when the cord is short and the area therefore cou- 

 centratedj then the visibility is great, aud vice versa. 



26* 



