(harp eye,) without the affiftance of a glafs ; fo that 
even taking up the water and examining it affords to 
the vulgar no fatisfadtory 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 leaf!: appearance of difcolora- 
tion in the water : the whole furface appeared as if 
covered with florid blood. It fhould be obferved that 
feveral other fpecies of animalcules fometimes give 
the fame tinge to ftagnant waters, though in a far lefs 
flriking degree: thus the monoculus pulex of Linnaeus 
is frequently fo numerous as to redden the water: the 
larva of the common gnat has alfo been known to pro¬ 
duce a fimilar difcoloration. 
Thefe are appearances which in lefs enlightened 
ages, unaflifted 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- 
curfors of fome great calamity, or magnified into the 
immediate fymptoms of heavenly difpleafure. We are 
affined by the celebrated Swammerdam that the city 
of Leyden was in a ftate of confternation on difcover- 
ing one morning that the waters of that place were 
apparently changed into blood ; which, upon accurate 
examination, was found to be owing to no other caufc 
than prodigious numbers of minute red animalcules, 
(in all probability of the very fame fpecies here repre- 
fented.) For the effect which fuch appearances pro¬ 
duced on the minds of the ancients, it may be fufficient 
to recal to the recolledtion of the reader the words of 
Virgil, 
