40 The Microscope. 



The scales of the green Forester-moth are somewhat 

 similarly inscribed, but not with equal distinctness. 



Let us again adjust the microscope to view 

 " opaque objects/' and feast our eyes on a few more 

 specimens of Nature's mosaic work. The wings of 

 butterflies and moths have been compared to patterns 

 in mosaic ; though of course there is this great dif- 

 ference, that the pieces of mosaic are inlaid ; whereas 

 the scales of these insects, as I have already said, lie 

 over each other like feathers, fishes' scales, or tiles on 

 a roof. Still their general flatness, and the fact of 

 their delicate shades being usually caused by hundreds 

 of minute scales the dark or light ones in greater or 

 less number according to the hue required originated 

 the comparison. 



I have examined some, however, in which the 

 effect of the shading is heightened in a way inadmis- 

 sible in mosaic work, but sometimes employed by 

 painters. It sometimes happens, that when an artist 

 is painting for instance a landscape and wishes 

 to bring out a rock or tree very vividly, he finds it 

 necessary to make a roughness on that part of his 

 canvas. A painter, whose works are familiar to 

 many, on one occasion actually made t)' ^ surface of 

 his picture rough by causing a small quantity of sand 

 to adhere to the canvas, and it had the desired effect 

 of giving brightness to what was then painted over it. 



Now there is a yellowish-brown insect called the 



power, although the additional size gained by further magnifying 

 makes it easier to engrave. The same remark applies to many othur 

 objects represented in this work. 



