110 CLASSIFICATION OF 



they have a mouth with palpi, a spiral tongue, and a 

 body set with hairs. The scales resemble feathers ; 

 they lie over one another, in an imbricated manner, 



between mosaic and the scales on the wings of papilionaceous 

 insects, is not less interesting. 



Mosaic work is of very ancient invention, but the moderns 

 have greatly improved the art. Pictures of various subjects 

 are formed of it, of amazingly fine workmanship ; imitations 

 of buildings, trees, ground of various kinds, and distant moun- 

 tains ; and the human figure, both singly and in groups. These 

 are produced by small pins, of variously coloured glass, stuck 

 into a kind of paste. They are so minute in many cases, that we 

 can hardly discern them to be an arrangement of an infinite 

 number of particles of glass ; they rather look like a picture 

 painted with the finest colours, harmoniously blended together. 

 The calculation made by Keysler is, that a piece of eighty 

 square feet, if perforated with tolerable care and delicacy, 

 would employ eight artists the space of two years. 



A small piece of the wing of Papilio lo, (the Peacock 

 Butterfly,) a quarter of an inch square, was cut out, and placed 

 under the third magnifier of an opaque microscope, when 

 seventy rows of scales were counted, and ninety in each row. 

 Consequently, there were six thousand three hundred scales 

 on one side of this small portion of wing ; so that the square 

 inch of a wing must contain the astonishing number of one 

 hundred thousand seven hundred and thirty- six scales. The 

 number of glass pins in a square inch of mosaic being only 

 eight hundred and seventy, the coarseness of such a picture, 

 compared with the mosaic of the wing of this insect, is in the 

 proportion of one hundred and fifteen at least to one ; that is, 

 such a picture is one hundred and fifteen times coarser than 

 this natural mosaic. 



The Peacock Butterfly is one of medium size, and the scales 

 on it are in proportion to its size. What then n^ust be the 



