340 ANNUAL OF SCIENTIFIC DISCOVERY. 



de Verd shower of 1834 had a breadth, according to Darwin, of more 

 than 1600 miles, and extended from 800 to 1000 miles from the African 

 coast. This gives an area of 960,000 to 1,648,000 square miles. The 

 surface of Italy and Sicily is about 100,000 square miles ; a single dust- 

 shower covering both these countries, like that of 1803, or of Lyons 

 in 1846, would deposit 112,800 weight of dust in a single day. With 

 such facts before us, Ehrenberg asks, how many thousand millions of 

 hundred weight of microscopic organisms have fallen since the period 

 of our earliest record of such events ? He adds, " I can no longer doubt, 

 that there are relations, according to which living organisms may 

 develop themselves in the atmosphere ;" and he speaks of this as a 

 self-development, and not a production from introduced ova. He sup- 

 poses it probable that the atmospheric dust-cloud region is of vast ex- 

 tent, and is above a height of 14,000 feet. These facts may seem in- 

 explicable on any other hypothesis ; yet much more investigation will 

 be required before an opinion, so contrary to received principles, can be 

 generally adopted. 



The number of dust showers which Ehrenberg records is in all 340 ; 

 81 before the Christian era, 249 after. The first instance he adduces, 

 is the plague of blood inflicted upon the Egyptians, as related in the 

 Mosaic history, which continued throughout all the land of Egypt for 

 three days and three nights. The second occurred about 1181, J3. C., in 

 the time of ^Eneas and Dido, as related by Virgil, ^neid, iv. 454, "Hor- 

 rcndum dictu, latices nigrescere sacros visaque in obscoznum se vertere 

 vina cruorem" Many other instances of subsequent date are also re- 

 corded, the information respecting which is not of as doubtful a char- 

 acter as with those referred to before the Christian era. 



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. They seldom reach 

 north as far as Russia and Sweden. This zone, in the North Torrid 

 Zone, has a breadth of 1800 miles. The reddish color of the dust, as 

 well as the organic forms, show that the dust is not of African origin. 

 Moreover the storm-winds and Sirocco are found to afford the same 

 species of organisms. The whole number of species of organisms ob- 

 served is 320. A simultaneous occurrence of dust-showers and falls of 

 meteoric stones has been observed in probably eighteen instances before 

 the Christian era. During the Christian era, fourteen coincidences have 

 been observed, making thirty-two in all. Compiled from Silliman's 

 Journal. 



STRUCTURE AND GROWTH OF ZOOPHYTES. 



A SINGULAR degree of obscurity has been thrown around the growth 

 of coral zoophytes and coral formations, through the various specula- 

 tions which have been offered in place of facts ; and, to the present 

 day, the subject is seldom mentioned without the qualifying adjective 

 mysterious, expressed or understood. Some writers, scouting the idea 



