M rc r o s c- opical Essays, gjn 



hereby able- to view it in any poll u re. From hence he collected, 

 that the extreme limits of the vibrations were ufually fomewhat 

 about the length of the body diftant from each other, often 

 fhorter, and fometimes longer. The foremofl limit was generally 

 a little above the back, and the hinder one fomewhat beneath the 

 Kelly ; between thefe, to judge by the found,, they feemed to 

 move with an equal velocity, The manner of their moving 

 them, if ajuft idea can be formed by the ihadow of the wing, and. 

 a confideration of it's nature and ftruclure, feemed to be this : 

 the wing being fuppofecl to be in the extreme limit, it is then 

 nearly horizontal, the fore part only being a little depreffed ; in 

 this fituation the wing moves to the lower limit ; before it arrives 

 at this, the hinder part begins to move fallen 1 ; the area of the 

 wing begins to dip behind, and in that pofture it feems to be 

 moved to the upper limit back again. Thefe vibrations (judging 

 by the found, and comparing them with a firing tuned in unifon 

 thereto) con fi ft of many hundreds, if not thoufands, in a feeond 

 of time. The powers of the governing faculty of the infect, and 

 the vivacity of it's fenfations, whereby every organ is Simulated 

 to a6l with fo much velocity and regularity, furpafs our prefent 

 comprehenfion. . 



Fig. l, Plate XV. is a reprefentation of the wing of the heme- 

 robius perl a (Lin. SyfL Nat. vol. i, part 2, page 911-2) of the 

 natural fize. Fig. 2 reprefents the fame wing magnified. This 

 elegant infec~l has acquired the name of hemerobius from the 

 mortnefs of it's life, as it feldom lives more than two or three 

 days in it's fly Hate : Linnaeus has placed it in his fourth clafs, 

 among thole infecls which have four tranfparent wings and no 

 fting. The wings are nearly of a length, and exaaly fimilar; 



tliey. 



