ASH DEPOSITS ON THE OCEAN FLOOR. 183 



fowls went to roost. At twelve o'clock on the following day, objects 

 could be distinguished at a distance of twelve yards, but the light 

 was thus obscured for two days longer. All the time a fine 

 impalpable white dust fell, which covered the ground at San Antonio 

 to a depth of 2 J inches, in three layers ; the lowest dark, the next 

 greyish, and the upper whitish. The light continued partly obscured 

 for twelve days more the darkness, of course, being due to the 

 quantity of ash in the air. At Nacaome, 24 miles north, the ashes 

 which fell four or five inches deep, had a fetid, sulphurous smell. 

 On the 23d, the sky was light enough to show that a fresh eruption 

 had taken place ; and in three hours darkness returned as on the 

 2oth. When the atmosphere became clearer next day, the houses 

 were covered with ashes to a depth of eight inches. Twenty-four 

 miles south of the crater, ashes covered the ground to a depth of more 

 than 10 feet, destroying pine woods. The thickness of the ash 

 deposit varied somewhat with the wind, but so fine was the dust 

 that it was carried as far as Chiapa, 1200 miles to the north, while 

 at St. Ann's, in Jamaica, 1700 miles N.E., the sun was obscured on 

 the 24th and 25th of January, and showers of fine ashes fell over 

 the whole island, so that they must have travelled at the rate of 

 170 miles a day. 



The surface of the Pacific, uoo miles S.E. of the volcano, was 

 covered with ashes, and a ship ran through 40 miles of floating 

 pumice. This eruption of Coseguina is especially interesting, because 

 Aconcagua and Corcovado were active at the same time. 



The eruption of Vesuvius in 472 is said to have covered all 

 Europe with ashes which even fell in Constantinople ; and on various 

 occasions the ashes from the volcanoes of Iceland have covered the 

 North Sea, and fallen in Scandinavia. Perhaps the most remarkable 

 evidence, however, of the extreme fineness of the dust is furnished by 

 those great deposits of red clay which characterise the central regions 

 of the Atlantic and Pacific Oceans. 



Red Clay in the Deep Sea. Mr. Murray reports that the deep- 

 sea clays and deposits at a greater depth than 2000 fathoms appear 

 to be always due to the decomposition of ashes and volcanic materials. 

 The red clays owe their colour to oxide of iron ; the chocolate-coloured 

 clays are tinged with oxide of manganese, a mineral that abounds in sea- 

 bed regions covered with augitic materials. Most of these clays con- 

 tain little carbonate of lime, and those of the North- West Pacific 

 abound in siliceous organisms. Amorphous matter rarely makes up 

 one-half of the clay, and the remainder consists of quartz, mica, pumice, 

 peroxide of manganese, and other minerals. Peroxide of manganese 

 is always present, and sometimes makes up one-half the deposit, but 

 quartz and mica are only characteristic of the North Atlantic. Occasion- 

 ally copper, cobalt, and nickel are found in the clays. Pumice and 

 scorias are universally distributed, some of the bottoms at 2900 fathoms 

 being largely made up of finely-divided pumice. Pumice was dredged 

 by the Challenger in at least 80 stations in masses from the size of a 

 pea to that of a cannon-ball, and is most abundant in the neighbour- 



