ftiarp eye,) without the affiftance of a glafs ; fo that 

 even taking up the water and examining it affords to 

 the vulgar no iatisfadtory elucidation. I remember to 

 have more than once obferved the whole furface of a 

 large moat or pool completely covered in the fpace of 

 a fingle night with this animalcule, when the day 

 before there was not the leaft appearance of difcolora- 

 tion in the water : the whole furface appeared as if 

 covered with florid blood. It mould be obferved that 

 feveral other fpecies of animalcules fometimes give 

 the fame tinge to ftagnant waters, though in a far lefs 

 Unking degree : thus the monoculus pulex of Linnasus 

 is frequently fo numerous as to redden the water : the 

 larva of the common gnat has alfo been known to pro- 

 duce a iimilar difcoloration. 



Thefe are appearances which in lefs enlightened 

 ages, unaffifled by the microfcope, have fo often filled 

 the minds of the people with the moft terrible appre- 

 henfions, and have been regarded either as the pre- 

 cursors of fome great calamity, or magnified into the 

 immediate fymptoms of heavenly difpleafure. We are 

 afiured by the celebrated Swammerdam that the city 

 of Leyden was in a ftate of confirmation on difcover- 

 ing one morning that the waters of mat place were 

 apparently changed into blood ; which, upon accurate 

 examination, was found to be owing to no other caufe 

 than prodigious numbers of minute red animalcules, 

 (in all probability of the very fame fpecies here repre- 

 fented.) For the effed which fuch appearances pro- 

 duced on the minds of the ancients, it may be fufficient 

 to recal to the recollection of the reader the words of 



Virgil, 



