FRESH-WATER ALG. 227 
handed down as such to our own times. We be- 
lieve the facts ; but we do not believe the explana- 
tion given of them, or the inferences deduced from 
them ; our superior scientific knowledge enabling 
us to account, on natural grounds, for what, in an 
age of ignorance and superstition, appeared pro- 
digies of fatal presage. 
Instances of such phenomena are to be met with 
in the earliest literary remains. Homer tells us 
in the /ad that before the death of Sarpedon 
‘The weeping heavens distilled 
A shower of blood o’er all the fatal field.’ 
During the first great plague of Rome, in the reign 
of Romulus, we read in Plutarch that it seemed to 
rain blood; and also that when Flaminius and 
Furius were leading an army against the Isubrians, 
the river which ran through the Picene was seen 
flowing with blood. Livy relates that the Alban 
water flowed in a bloody stream, and that this and 
other prodigies were expiated by sacrifices. Quintus 
Curtius mentions the occurrence of blood-rain near 
the end of the siege of Tyre by Alexander the 
Great, staining the bread of the Macedonian 
soldiers as well as of the besieged Tyrians, but 
frightening the latter into surrender. Ehrenberg 
has given a very full and exhaustive account of 
these curious portents, from which I shall give a few 
selections. In the middle of the ninth century, red. 
