factures, and commerce, of mining and building, of inventing and executing in every land-Colleges in which great chemists, great mechanics, great naturalists, great inventors, are already working, in a professional manner, to aid and develope all that capital, skill, and enterprise can do. Coming from such Colleges to the central University, may we not well look upon it as a great epoch in the life of the Material Arts, that they have thus begun their university careerthat they have had the advantage of such academical arrangements as there have been found, and still more, as I have said, that they have had the greater advantage of intercourse with each other? May we not expect that from this time the eminent producers and manufacturers, artizans and artists, in every department of art, and in every land, will entertain for each other an increased share of regard and good-will, of sympathy in the great objects which man's office as producer and manufacturer, artizan and artist, places before him-of respect for each other's characters, and for the common opinion of their body, all increased by their being able to say, "We were students together at the Great University in 1851."

On the Infusoria and other Microscopic Forms in Dust-showers and Blood-rain. By Dr C. G. Ehrenberg.

The infusorial character of the dust occasionally transported by winds, is one of the most interesting of Ehrenberg's discoveries. His investigations have been reported from time to time in the Berlin Memoirs and elsewhere, and notices of some of his results have appeared in this journal. A memoir in the Memoirs of the Berlin Academy contains the details of his various researches, with full pictorial illustrations. The plates contain, not only figures of all the forms observed in each case, but a sketch of a portion of the dust as it lay under the field of his microscope, exhibiting to the eye the relative prevalence of different forms, and the colours

*

* Vide Passatstaub und Staubregen. Grosses organisches unsichtbares Wirken und Leben in der Atmosphäre. Von Hrn. Ehrenberg. Abhandlungen der Academie der Wissenschaften zu Berlin, 1847.

they presented. The showers, whose microscopic organisms are here reported, are as follows:

I. In the Atlantic, latitude 17° 43′ N., and longitude 26° W., about 500 miles from the coast of Africa.-The dust was collected by Mr Darwin, from the ship in which he was at the time. The direction of the wind was from the African coast. The dust resembled volcanic ashes, although evidently not of this origin, and about a sixth part of it was silicious shells of fresh water and land infusoria, and silicious phytolites,eighteen species of the former, and as many of the latter. The most of the forms are European, and none exclusively African. Among them there is the South American species Himantidium papilio, which occurs at Cayenne, and also a Surirella, probably from the same continent. The conclusion follows, as Ehrenberg observes, that either the dust came in part from South America, in the upper regions of the atmosphere, or these two species are yet to be discovered elsewhere.

II. Other Dust-showers in the Atlantic, from the Collections of Mr Darwin. These collections were made between the years 1834 and 1838, in latitudes 15°, 17°, 19°, and 21°, part at San Jago (Cape Verds), and part within 250 miles of the land, in the open sea, between longitudes 22° and 26°. They afford thirty new forms to those of the shower above noticed, and include also the same South American forms, Himantidium papilio, and Surirella Peruviana. In addition, there are three species of Eunotia, which have been found only in Senegambia and Guiana, together with the Amphidiscus obtusus, also South American. Besides the others, there was one Polythalamium, making in all 67 organic forms. The only new species was the Eunotia longicornis, which is very similar to a Hungarian fossil species. No species peculiarly African was found in the dust. One, the Lithostylidium Rajula, occurs at the Isle of France.

III. Dust which fell at Malta, 15th of May 1830.—This dust was obtained by Mr Darwin from purser R. G. Didham, of the ship Revenge. The wind at the time was east-southeast, and a similar fall of dust took place at the time, in the bay of Palmas, in Sardinia. The number of species afforded was 43, of which 15 were Infusorial, 21 Phytolitharia, and 7 Polythalamia.

Some of the species occur in Africa, yet

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.