After a shower of rain which extended over several of the Western States, on Friday the 25th ult., a substance resembling sulphur was observed in various localities, especially in the neighborhood of Louisville. The Courier of that city says : " On Saturday morning the streets and all the pools of water for miles around were discovered to be covered with a fine yellowish dust, which many have supposed to be sulphur ; in fact, we are informed that some ot the dust was gathered, and upon fire being applied it burned the same as sulphur. We, however, are not inclined to any such opinion, but believe the substance to have been no other than the pollen ot plants or trees and scattered by the winds.— Its appearance on the waters is a thing of common occurrence at this season, particularly in those parts of the State of Louisiana and Mississippi where the pine and cypress abounds." The Cincinnati papers also notice the phenomenon as it was observed in that city.— [Exchange. [It was doubtless the pollen of plants and trees blown across the continent, which is of common occurrence in the southern part of the Union at this period of the year. [for the Scientist! American.]