INTRODUCTION. 



1 O thofe who are acquainted with tlie works of Mr. Leemven- 

 hoek, or who have been much converfant in INIicrofcopical ftudies, 

 this hitrodu61:ion may appear unneceflary : but thofe to whom the 

 fubjecl is new, ^^■iH find fo many wonders laid open to their view, 

 as perhaps to induce a doubt of the Author's accuracy in his obfer- 

 vations, or his veracity in his narrations. Indeed, the extreme mi- 

 nutenefs of many of the fubje6ts on wliich he treats, is in fome 

 inflances beyond the reach of our capacities to comprehend,* althougli 

 we may be fully adured of their exiftence. In fadi, it appears by 

 Mr. Leeuwenhoek's writings, that the difficulty now ftated, was 



* The Spcdtator, in one of his papers on the Pleafures of the Imagination, has a paffage 

 full to the prcfent purpc fe, which is as follows : 



' Nothing is more plsafant to the fancy, than to enlarge itfelf by degree?, in its contem- 

 ' plation of the various proportions which its feveral objefts bear to each other, when it com- 

 ' pares the boJy of man to the bulk of the whole earth, the earth to the circle it defcribes round 

 ' the fun, that circle to the fphcre of the fixed flats, the fphere of the fixed ft ars to the circuit 

 ' of the whole creation, the whole creation itfelf to the infinite fpace that is every where dif- 

 ' fufcd about it: or when the imagination works downward, and confiders the bulk of a human 

 •■ body, in rcfpect of an animal a hundred times Icfs than a mite, the particular limbs of fuch 

 ' an animal, the different fprings which a^^uate the limb?, the fpirits which fet thcfe fprings a 

 ' going, and the proportionable minutencfs of thtfc ftvcral parts, before they have arrived at 

 ' their full growth and perfetStion. But if, after all this, we take the leaft particle of thefc 

 ' animal fpirits, and confider its capacity of being wrought into a world, that fliall contain 

 ' within thofe narrow dimenfions a heaven and earth, ftars and planets, and every different 

 ' fpecics of living crcatur:?, in the fnme analogy and proportion they bear to each other in our 



a 



