ITALIAN AND CALABRIAN DUST-SHOWERS.

251

in others of lime, united with oxide of iron. In some cases it is combustible.

627. When the loricated infusoria die, their shells remain undecayed for ages, often congregated in such countless myriads as to form large portions of the earth's surface.

The city of Richmond, in Virginia, is built upon an extensive bed of flinty marl, from twelve to twenty feet in thickness, filled with fossil, infusorial shells; and it is stated by geologists, that nearly half of the bulk of all the chalk of Northern Europe is composed of the fossil remains of animalcules, and other minute shells. They are mingled with the mud that forms the bed of the Arctic Ocean; they float with the iceberg in all its wanderings, and lie loosely scattered over the surface of every land. These hieroglyphics of nature are interpreted by the aid of the microscope.*

628. THE ITALIAN DUST-SHOWER OF 1803, and the CALABRIAN OF 1813. In the dust which fell in Italy during the month of March, 1803, forty-nine species of organic structures were discovered, and sixty-four in that which descended at Gerace, in Calabria, in 1813. Thirtynine species in the Italian dust-shower, and fifty-one in the Calabrian, are identical with those discovered in more recent dust-storms. It is worthy of remark, that these two storms, though ten years apart, have no less than twenty-eight species in common, and in both nearly all the species are of fresh-water origin. Among the numerous infusorial shells, four South American forms were discovered; of these, one occurs in Peru, another in Surinam, and the remaining two belong to Chili. No animalcular structures were found exclusively African.

629. ATLANTIC AND CAPE DE VERD DUST. The dust

When the loricated infusoria die, what becomes of their shells? Of what did the dust consist which fell in the Italian and Calabrian dust-storms?

*For further information on the subject of Living and Fossil Infusoria, see "Views of the Microscopic World," by the author; published by Farmer, Brace & Co., New York.

that was collected by Mr. Darwin on the Atlantic, in N. Lat. 17° 43', W. Long. 26°, and at the distance of about five hundred miles from the African coast, was submitted to the examination of Ehrenberg, who discovered that one-sixth part of it was composed of the flinty shells of fresh water and land infusoria, and of silicious fossil plants. There were eighteen species of the former, and as many of the latter. Of the animalcular remains, the greater part were European; one species was decidedly of South American origin, and another probably; but there were none that belonged exclusively to Africa. In the opinion of Ehrenberg, the two South American species were either brought from that country by the upper winds of the atmosphere, or from some other locality which is yet unknown.

630. In the dust of several other showers, which occurred between the years 1834 and 1838, some at St. Jago, and some on the neighboring ocean, numerous organized structures were discovered, thirty of which were different from those detected in the dust just described. Among these were the shells of a few South American infusoria, and one beautiful microscopic shell, termed the Polythalamia, or many-chambered shell. A single species was observed that occurs in the Isle of France; but none of the forms were recognized as peculiarly African.

*

631. Some of the dust collected by Mr. Ewbank, on his voyage to Rio Janeiro, was examined by Professor Bailey, of West Point; but he was unable to discover in it any thing besides irregular, inorganic, mineral fragments. He believes, however, that more interesting results would have been obtained if the dust had been gathered with greater care. The entire number of distinct organic

Relate, in full, what is said respecting the composition of the Atlantic and Cape de Verd dust.

What is said respecting the dust of several other showers?
Were any of the forms distinctively African?

Were any organisms discovered in the dust collected by Mr. Ewbank?

What is, however, the opinion of Prof. Bailey?

* From polus, (Greek,) many, and thalamus, (Latin,) a chamber.

forms hitherto discovered in the Cape de Verd and Atlantic dust-storms is sixty-seven.

632. SIROCCO DUST. The dust that fell at Malta on the 15th of May, 1830, afforded forty-three distinct organized forms; of these there were fifteen infusorial structures, twenty-one kinds of minute, petrified plants, and seven of Polythalamia. The species of animalcules were, for the most part, identical with those discovered in the Cape de Verd and Atlantic dust-showers.

One form was noticed belonging peculiarly to Chili, but none were found distinctively African.

State the entire number of organic forms hitherto detected in the Cape de Verd and Atlantic dust-storms.

633. The Sirocco dust that fell at Lyons, on the 17th of October, 1846, was so rich in organic remains that they constituted one-eighth part of its mass. They consisted of numerous species of infusoria and of petrified plants, mingled with a few kinds of Polythalamia, and minute, vegetable fragments. The species were nearly all of fresh-water origin, one-seventh only being marine. In figures 45 and 46 are delineated the various microscopic

MICROSCOPIC ORGANISMS OF THE LYONS DUST-SHOWER.
(Fossil Plants.)

organisms which were discovered in this dust. The most remarkable circumstance respecting it is the fact, that, notwithstanding its general resemblance to the dust of the Atlantic showers, which has always exhibited nothing but dead and empty infusorial shells, this, on the contrary, was found, in many cases, to contain a species of

Describe the nature of the Sirocco dust that fell at Malta and at Lyons.

What is remarkable respecting the Lyons shower?

infusoria which was distinctly seen to be filled with green ovaries, or egg-sacks, and consequently was capable of life.

634. The dust collected, in the preceding instances, from the Cape de Verd, Atlantic, and Sirocco showers, being nine in all, afforded 119 distinct organisms. Of these there were fifty-seven species of infusoria, and eight of Polythalamia; forty-six kinds of fossil plants, together with particles of seven kinds of plants, and one fragment of an insect. Only seventeen of these organisms were marine; while 102, six-sevenths of the whole, consisted of fresh-water species. In all these showers the dust exhibited no indications whatever of volcanic origin.

635. In three dust-showers which occurred in the years 1847 and 1848-the first in Salzburg, the second in Arabia, and the third in Silesia and Lower Austria-similar fresh-water organisms were detected. The same South American species were here found, as in other showers, without any characteristic African forms.

636. The red snow that fell in the Tyrol on the 31st of March, 1847, afforded sixty-six different organic forms. Of these, twenty-two were infusorial structures, twentyeight fossil plants, two polythalamia, and thirteen particles of plants. There was also one fragment of an insect. The greater part, by far, of all these species, were of land origin, two only being marine.

A remarkable resemblance exists between the coloring matter of this shower and the dust of the Atlantic, Genoese, and Lyons storms, not only in its hue, but in its composition; for out of these sixty-six structures, forty

How many distinct organisms were discovered in the dust of nine showers? Describe the several kinds.

Was there any trace of volcanic dust in these showers?

What is observed respecting the dust-storms which happened in the years 1847 and 1848?

What organisms were detected in the red snow of the Tyrolese storm?

What resemblance was observed between the coloring matter of this shower and the dust that fell on the Atlantic, at Genoa, and at Lyons?