THE ERUPTION OF VESUVUTS IN APRIL, 1906. 235 



moisture, and became imnu)bile, and erosion exposed ii-regiilar 

 lines of lamination. The action of light rains accompanyino; or 

 immediately following the fall produced granulation. No granules 

 were observed, however, as large as peas, such as are common in the 

 Antilles and also in ash beds of Pompeii. The conditions most 

 favorable to the production of this structure are fineness of grain and 

 a succession of showers insufficient to soak the material. The first 

 condition is ' illustrated at Pompeii, where the pisolites are found 

 only in the upper and finest part of a bed. When the precipitation 

 is great at the time of an ash fall, a mud is produced which can unite 

 into small glol)ules before reaching the ground. 



The distribution of the ash being determined b}^ the Avind is very 

 irregular in the Yesuvian area. On the other hand, in the Tropics, 

 where trade winds prevail, the dissymmetry of these deposits, with 

 reference to their source, is a characteristic feature. The thickness 

 of the deposit ranged from 3 centimeters at Xaples to 20 centimeters 

 at the base of the volcano. The portion that reached the higher 

 regions of the atmosphere was transported far beyond the bounds of 

 Italy. 



On the flanks of the volcano, and particularly near the crater, the 

 ash has contributed to the formation of dust spouts, flaring above and 

 terminating at the surface in a narrow stem. They had a very rapid 

 gyratory movement and a slow movement laterally. 



The fine ash which covered the vegetation seemed at first to destroy 

 all things, but the buds of the vines being still closed the destruction 

 was less than was expected, and at the beginning of Ma}'^ the country 

 was again luxuriantly green. The floating fauna in the Bay of 

 Naples is rejDorted to have suffered much by the eruption and also 

 some of the animal life at the bottom of the bay. 



An observation was made — interesting to paleontologists studying 

 problematic organisms — concerning animal trails. At the beginning 

 of the eruption where the ash was light and uncompacted numerous 

 and varied trails were to be seen made by lizards, small snakes, and 

 coleoptera. At the end of the trails made by the last-named, the 

 animal itself could often be found still living or entombed in the ash. 



II. FUMAROLES AND PRODUCTS OF ERUPTION. 

 PUMA ROLES. 



Previous eruptions of Vesuvius have played an important part in 

 the acquisition of definite knowledge regarding volcanic fumaroles. 



Fouque has shown that the chemical composition of a fumarole is 

 essentially a function of its temperature. The fumaroles of high 

 temperature spring only from flowing lava and furnish white subli- 

 mates of the alkaline chlorides, associated at times on Vesuvius with 



