“_Manna._--An account of manna ‘rains’ certainly pertains to the discussion of showers of vegetable matter, for the substance manna consists of lichens of the genus _Lecanora_ but in none of the numerous recorded instances of manna ‘rains’ is there any direct evidence that the substance really fell from the sky. These lichens form small, round bodies that are easily blown over the surface of the ground and accumulate in depressions; they are very buoyant also and hence easily drifted into masses during the run-off of rain water. Manna ‘rains’ have not occurred except in countries where these lichens are common, and as for statements of their falling down upon roofs or upon people, or for any other proofs that they really rained down, I have seen none. “_Blood rains._--The most frequently reported showers that are spurious, at least in name, are the so-called blood rains. In all times the phenomena going under this name have frightened the people and have been taken as portents of terrific calamities. One of the famous plagues of Egypt was a bloody rain which prevailed throughout the whole land, continuing three days and three nights. Homer and Virgil both allude to blood rains, and, in fact, the general subject of preternatural rains was a favorite with the older writers. “But scientific investigation has done away with the element of mystery in these phenomena and has explained, with the others, the rains of blood. Some blood rains have been found to be the meconial fluid ejected by large numbers of certain lepidoptera simultaneously emerging from their chrysalides; other red rains are due to the rapid multiplication in rain pools of algæ and of rotifers containing red coloring matter; “red snow” results from the presence of similar organisms. But in no case have they rained down, except in the sense that their spores or eggs have at some time been transported, probably by the wind. The precipitation of moisture furnishes favorable conditions for their rapid development and multiplication.” Most of the reported showers of blood, however, have probably been rainstorms in which the rain was colored with reddish dust. The occurrence of such dust in the atmosphere is very common in some parts of the world, as we have stated in a previous chapter. It has been asserted that rain which fell at Oppido Mamertina, Italy, May 15, 1890, actually contained blood, believed to be from birds. Showers of supposed “sulphur” are due to pollen, chiefly from pine trees. The air in the vicinity of pine forests is sometimes filled with clouds of this material and the wind carries it for many miles. It is reported that a pollen shower at Pictou, Nova Scotia, in June, 1841, was so heavy that bucketfuls were swept up on a ship. In the case of alleged showers of “paper” the material has been found to be the crusts of dried algæ, which form on the surface of the ground exposed by the evaporation of the water of shallow ponds. 6. THE YEAR WITHOUT A SUMMER