UBIQUITY OP DIATOMACE.E. 209 



up with the lead. Here then was a submarine deposit 

 in process of formation equalling in extent any similar 

 deposit of the earlier world. Such strata are doubtless 

 in course of accumulation in most parts of the ocean, 

 and may be observed on our own shores ; but this Ant- 

 arctic bank is the grandest example of the kind which 

 has been carefully investigated by an able naturalist. 

 But it is not only the sea and the land which yield the 

 relics of these plants j the Diatomacece perform long 

 journeys through the air ! This remarkable fact rests 

 on the authority of the accurate Darwin, who collected 

 at sea small dust, which fell from the atmosphere on 

 the planks and rigging of the ship, which dust, when 

 examined by the microscope, was found composed of 

 Diatomacece. These were on their flight from America 

 to Africa. From their silicious nature they resist even 

 the strong heat of volcanoes, and their remains are 

 found thrown up in the pumice and dust from the 

 crater. In fact, it is difficult to name a nook on the 

 face of the earth, or in the depths of the sea, where they 

 are wholly absent, either in a dead or living state ; and 

 their office in the general economy, besides affording 

 food for the humbler members of the animal kingdom, 

 seems to be the preparation of a soil for a higher class 

 of vegetables. This they effect by the minute division 

 of the silicious particles laid up in their tissues, and 

 probably make this nearly insoluble earth more fit for 

 assimilation by other plants. We must also suppose 

 them endowed, like other vegetables, with the power of 

 decomposing carbonic acid and liberating oxygen; and 

 thus, in their countless myriads, exercising no mean 



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