there are no characteristic African forms-and although such showers, with the hot winds that attend them, are usually referred to the Sahara desert, they appear to be quite foreign to that region. Among the species, Synedra entomon is a characteristic form from Chili. In general character, the species are like those of the Cape Verd and other showers.

IV. Sirocco dust of Genoa, May 16, 1846.-In this dust, Ehrenberg found 22 species of Polygastrica, 21 of Phytolitharia, and 3 of parts of plants. The forms have much resemblance to those of the Malta and Atlantic showers. The colour is yellowish or ochreous, from oxide of iron, and not grey like the true African dust, and about one-sixth to onethird of the mass is organic. None of the species are characteristic African forms, and Synedra entomon is South American.

It follows from the preceding results that the showers of the Atlantic, of Malta and of Genoa, are in general alike, in organic, as well as inorganic constitution, and in the absence of characteristic African forms; and this resemblance is the more surprising, as the observations extend through the long period of 16 years, from 1830 to 1846. They are alike, also, in the brownish red colour of the dust.

V. Sirocco dust of Lyons, Oct. 17, 1846.—The Lyons shower afforded 39 species of Polygastrica, 25 of Phytolitharia, 3 of Polythalamia, besides minute portions of plants. In this shower, the organic forms make up about one-eighth of the mass. In general character, including colour, there is a close resemblance to the products of the Atlantic showers and the others above described. The species are nearly all of fresh-water or land origin; one-seventh only are marine species. The most abundant forms of Polygastrica are Eunotia amphioxys, E. gibberula, E. longicornis, Gallionella decussata, G. granulata, and G. procera; and those of Phytolitharia, Lithostylidium Amphiodon, L. ossiculum, and L. rude.

There are two South American species, the Eunotia Pileus and Himantidium Zygodon.

The number of species brought to light from the dust of nine showers thus far described, is as follows:

Polygastrica, 57; Phytolitharia, 46; Polythalmia, 8. Besides these, there are seven kinds of particles from plants, and are fragments from an insect. Seventeen of the species are marine, and the other 102 of fresh-water origin. There is no evidence of volcanic origin.

VI. Second specimen from the Genoa shower of the 16th of May 1846.-All but one of the forms mentioned were observed in the former specimen of the dust.

VII. Storm of red snow in Puster Valley, in Tyrol, March 31, 1847.-This red snow owed its colour to a coloured dust, much resembling that of the Atlantic. Its tint is brownish red.

It afforded, as obtained at two localities, 66 organic forms, 22 of which were Polygastrica, 28 Phytolitharia, 2 Polythalamia, 13 particles of plants, and 1 of an insect. The large majority of the species are known fresh water and continental forms; only 4 to 6 species are unknown, 2 are marine, namely, Coscinodiscus radiolatus, and a Spiroloculina (?). There is a remarkable resemblance in the colour and character of the dust to that of the Atlantic, Genoa, and Lyons, and an identity in many of the species; 46 species out of the 66 occur in the Sirocco and Atlantic dust; 12 Polygastric species, and 20 Phytolitharia are common to the Atlantic showers and the Tyrolese snows. This uniformity of character over regions so widely separate, yet in nearly a common latitude or zone, and in so many distinct examples through a number of years is most surprising.

VIII. Dust which fell in Italy in 1803, and in Calabria in 1813. The former of these showers is represented as coming from the south-east. It afforded 49 species, and that of Calabria 64. Out of the 49, 39 have been observed in the more recent showers; and out of the 64, 51 are like the more recent. These showers, although ten years apart, have 23 species in common, or about one-fourth. In both nearly all the species are of fresh water or continental origin. In both, as in other showers, the most abundant species are Eunotia amphioxys, Gallionella granulata, G. crenata, G. distans, G. procera, Lithodontia, Lithostylidia. In both, also, there are four South American forms; Coscinodiscus flavicans from Peru and St Domingo; Navicula undosa from Surinam; Stauroneis

linearis from Chili and North America; Synedra Entomon from Chili. The last occurs also in Africa and Asia. There are no characteristic African species.

Ehrenberg next mentions facts of a similar kind of earlier date. Humboldt when in Paramo, on the way from Bogota to Popayan, at a height of 2300 toises (14,700 feet), observed a red hail, a fact published by him in the Annales de Chemie for 1825. The height of the place gives peculiar interest to the observation.

In 1755, on the 14th of October, at 8 o'clock in the morning, a warm Sirocco wind was blowing at Locarno, near Lago Maggiora. At 10 o'clock the air was filled with a red mist, and at 4 o'clock, P.M. there was a blood-red rain, which left a reddish deposit, equal to one-ninth of its mass. There fell 9 inches of this rain in one night. About 40 square German leagues were covered with this bloody rain, which also extended on the north side of the Alps into Suabia, and 9 feet of reddish snow fell upon the Alps. Supposing that the deposit averaged but two lines in depth, there would be for each square English mile an amount equal to 2700 cubic feet. But actual measurement gave for the depth in some places about one inch (or th of 9 inches).

In 1623 there was another blood-rain at Strasburg. It happened on the 12th August, between the hours of four and five in the afternoon. In the year 1222 a similar rain fell at Rome for one day and night. Many other like facts are cited.

Ehrenberg favours the view of the atmospheric origin of these showers, and speaks of their relation to the fall of aerolites. Chladni, in his work on Meteorites, observes that the stones which fell between 1790 and 1819, amounted to not less than 600 cwt.; while for the single dust-shower of Lyons in 1846, the material that fell was full 7200 cwt. The Cape Verd shower had a breadth, according to Darwin,* of more than 1600 miles, and according to Tuckey, of 1800 miles, and extended 600 to 800 miles, or even 1000 miles from the African coast. This gives an area of 960,000 to 1,280,000, or from 1,648,000 to 1,854,000 square miles.

Quarterly Jour. Geol. Soc., No. 5, 1846, p. 26.

The surface of Italy is about 90,000 square miles; that of Sicily 10,000 square miles, making together 100,000. A single dust-shower, covering both countries like that of 1803, to the extent of that of Lyons in 1846, would deposit 112,800 cwt. of dust in a single day. With such facts before us, Ehrenberg asks, how many thousand millions of hundredweight of microscopic organisms have reached the earth since the period of Homer, the time of our earliest record of such events? He adds, "I cannot longer doubt, that there are relations according to which living organisms may develope themselves in the atmosphere;" and he speaks of this as a self-development and not a production from introduced ova. He supposes it probable that the atmospheric dustcloud region is of vast extent, and is above a height of 14,000 feet. The facts may seem inexplicable on any other hypothesis; yet much more investigation will be required before an opinion so contrary to received principles can be generally adopted.

Showers of Blood.

The work proceeds with a historical relation of all showers of dust, blood-rain, red snow, and similar phenomena, from the earliest records to the present time. This history occupies 100 pages of the volume.

The first instance adduced dates about 1500 years before the present era. It is the plague of blood inflicted upon the Egyptians, as related in the Mosaic history, which prevailed throughout the whole land of Egypt, continuing three days and three nights.

The second occurred about 1181 B.C., the time of Æneas and Dido, as related by Virgil, Æneid iv., 454 :—

"Horrendum dictu, latices nigrescere sacros.

Visaque in obscoenum se vetere vina cruorem."

The third, about 950 B.C., as described by Homer, Ilias xi., v. 52, 54, and also Ilias xvi., v. 459, 460.

The fourth, about 910 B.C., is the instance of bloody waters mentioned in connection with the victory over the Moabites in 2 Kings iii., v. 21, 22, 23.

Ehrenberg mentions then the rain of blood in the time of

Romulus, as related by Livy, and goes on with other accounts of subsequent date, with regard to which the information is not of as doubtful character as with those just alluded to.

A supplemental chapter contains a notice of meteoric dust showers since 1846. One on the 31st March 1847, in the valley of Gastein, in Salzburg; another in Arabia, January 24, 1848; another in Silesia and Lower Austria, January 31, 1848. The showers afforded similar fresh water and continental forms, with the same South American species before-mentioned, and no characteristic African form. Other showers occurred in 1849. In March there was a reddish dust fell at Catania in Sicily, during a south wind. On the 14th April, during a hail storm in Ireland, there was a black inky deposit, affording numerous microscopic organisms.

The number of showers which Ehrenberg records is in all 340, 81 before Christ and 249 after Christ. Ehrenberg remarks that these showers appear to prevail most within a zone extending from the part of the Atlantic off the west coast of Middle and North Africa, along in the direction of the Mediterranean Sea, reaching a short distance north of this sea, and continued into Asia between the Caspian Sea and the Persian Gulf, perhaps to Turkistan, Kaschgar, and China; and they seldom reach north to Sweden and Russia. This zone, according to the observations of Tuckey, has a breadth of 1800 miles in the north torrid zone. The reddish colour of the dust, as well as the organic forms, shew that the dust is not of African origin. Moreover, the storm winds and sirocco are found to afford the same species of organisms.

Ehrenberg repeats again his opinion that these phenomena are not to be traced to mineral materials from the earth's surface, nor to revolving masses of dust material in space, nor to atmospheric currents simply; but to some general law connected with the earth's atmosphere, according to which there is a self-development within it of living organisms.

J.

The whole number of species of organisms observed is 320. 1,200 e genera there are only the following: Coscinodiscus, Diploneis, Goniothecium, Grammatophora, and Biddul