NATURAL HISTORY. 177 



fly has put me in mind of it : the other day 

 we were sitting together in school, and the 

 wall over our heads was covered with com- 

 mon flies ; and when we came out, we were 

 talking about the way in which the fly stuck 

 to the wall without falling down ; and as we 

 could not tell what kept him up, we agreed 

 to ask you about it." 



" I will tell you, boys, very willingly. I 

 do not wonder that you were unable to tell how 

 the fly stuck to the wall ; for you never tried to 

 find out, and therefore could only guess at it." 



" And that is not a good way to find out 

 any thing, Uncle Philip ?" 



" No, boys ; though some persons much older 

 than you are, did nothing but guess about this 

 very thing, and guessed very far from the truth 

 too. Some thought that the fly had a sponge 

 in its foot, and squeezed a sort of glue out of 

 it which made it stick fast ; others said that 

 the glass or wall was so rough that the fly's 

 feet would catch hold of the little points upon 

 it ; but both were wrong." 



" How does it hold on, Uncle Philip ?" 



" Did you ever see what the boys call a 

 sucker, made of a piece of soft sole leather ? 

 That will show you how the fly's foot sticks 



