Relation of the most miraculous swarms of flies [electronic resource] : that were seen flying in innumerable bodies through London, and dropping in great heaps like showers of rain, and appearing as white as snow on the ground, on Saturday the 19th of July, to the great admiration of thousands of people, who stood to admire their vast numbers in several parts both of city, the suburbs, and in Southwark: with the opinions of most learned persons concerning this surprizing prodigy. Licensed according to order.