The superstition that water, under certain circumstances, assumed the hue of blood, as in the case of St. Tredwell's Loch in Orkney, &c., claims special attention. We call this belief a superstition, inasmuch as a special miracle was thought to be involved in the matter; but we nowadays know, that such appearances show themselves without any miracle at all, except the constant miracle without which there would be no natural law. Modern bacteriology has proved the existence of a certain microscopic plant, technically styled Hæmatococcus Pluvialis and popularly known in Germany as Blutalge. In "Notes and Queries" for 12th March, 1892, Dr. G. H. F. Nuttall of Baltimore, observes:--"In Central Europe it has been found in pools formed by the rain in rocky hollows and stone troughs, &c. Hæmatococcus often becomes intimately mixed with the pollen of conifers and minute particles of plants which are known to be carried hundreds of miles by occasional currents of air. The rain drops in the heavens condense about such minute particles, and in falling, carry them down to the earth's surface, where, under proper conditions, these little plants multiply with enormous rapidity." Dr. Nuttall adds, "Besides the Hæmatococcus Pluvialis, we have a Bacterium which has often deceived people into the belief that they were dealing with bona-fide blood. This Bacterium is easily cultivated in the laboratory. It is one of the so-called chromogenic or colour-producing Bacteria, and bears the name Bacillus Prodigiosus, on account of its exceedingly rapid growth. This very minute plant has undoubtedly been the cause of terror among superstitious people. The organism will only produce its colour in the presence of oxygen, and, as a consequence, red spots appear only on the surface of the moist nutrient medium on which it may fall." Undoubtedly some such explanation would account for certain red spots, alluded to by Mr. Hunt, which appeared from time to time on the stones in the churchyard of the Cornish parish of St. Denis. According to the belief of the district, the spots were marks of blood, and their appearance foretold the occurrence of some untoward event in English history.