THE GRAND ERUPTION OF VESUVIUS IN 1906 651 



Upon this is the surface layer of nearly white impalpable ash. Von 

 Buch, who observed the quite important Vesuvian eruption of 1794, 

 has given the order of colors, which, he states, was then recognized 

 as characteristic, to be black, bright gray, and white.' The falling 

 of the sahhia rossa during the late eruption was joyously hailed by 

 the Neapolitans as the beginning of the end. 



This red ash is probably of the same general characters as the 

 gray underlying material, save for its finer state of subdivision and the 

 greater oxidation of the contained iron. Its fall appears to indicate 

 that, having been long suspended in the higher layers of the vaporous 

 atmosphere above the crater, the diminution in violence of the up- 

 rushing steam has left it without support and allowed it to settle. 

 The ultimate layer of nearly white material appears to be still more 

 finely divided. 



Effect of the projectiles upon windows. — The windows of Ottaiano 

 and San Giuseppe afford material for an interesting study. On 

 the sides of houses opposite the mountain they were broken in appar- 

 ently much more generally than on the side facing it, and even when 

 protected from falling blocks by deeply set casings. In several 

 of the windows specially examined possibihty of reflexion from 

 neighboring walls was excluded, and in all cases rather improb- 

 able. Sometimes almost entirely broken out, in other instances 

 they presented only a few cleanly cut holes almost perfectly circular 

 in form, and generally between two and three inches in diameter. 

 These holes were wholly devoid of radial fractures. Sometimes 

 two or more holes overlapped, but always with the same cleanly 

 cut outlines. Tn a number of cases the circular crack appeared, 

 but with the inclosed disk still in its place to indicate that the missile 

 had rebounded. The holes are clearly much larger than the flying 

 missiles which produced them. The large amount of ash in the air 

 at the time of the writer's visit to these cities made photographing 

 difficult, and the exposures from these windows were unfortunately 

 failures. 



The explanation of these fractured windows on the sides of build- 

 ings away from the volcano is probably to be found in the inrush 

 of air from all sides toward the crater to replace that removed by 



I L. V. Buch, Gesanimelte Schrijten, Vol. I, pp. 397-404. 



