344 



NATURE 



[Fed. 13, 1879 



tered red-hot masses in all directions. A piece -weighing 

 four ounces fell within six feet of where 1 was standing, 

 and the guide ran up to it and pressed a copper coin 

 upon its still soft surface. A few minutes later a piece 

 of red-hot lava, weighing at least seven times as much 

 as the preceding, fell within four feet of me, and I 

 promptly retired to a safer distance. Fifteen days before 

 a guide had been killed by a falling red-hot stone from 

 the crater. The projectiles from the crater are doubly 

 dangerous, because you cannot "dodge"' them. Theydo 

 not come down straight like a cricket-ball, but waver in 

 their flight like a boomerang. In the case of the larger 

 of the two masses which fell so near to me, I had not 

 only time before it fell to watch it in the air above my 

 head, but also to speculate as to where it would fall. 

 Judging by its position when about forty feet from the 

 ground, it would certainly, I thought, fall behind me ; a 

 moment later it swerved, and fell about four feet in front 



of me. The cone, with its lurid smoke, and loud detona- 

 tions, and showers of red-hot stones, presented a most 

 fascinating spectacle. What, then, must be the effect 

 when the whole great cone of Vesuvius is in a like 

 condition ? 



The new lava is very leucitic, and does not resemble 

 that of 1872. When in a viscous state it can easily be 

 drawn into threads, and when cold it is jet-black and 

 possesses a fine lustre. 



Chloride of ammonium does not appear to have been 

 at all a common product in this eruption, although it was 

 conspicuously present during the eruption of 1872. Great 

 differences of opinion still exist as to the formation of 

 sublimates of chloride of ammonium in lavas. Bunsen 

 considers that it is mainly formed by the action of the hot 

 lava upon vegetable soil, and he has proved that "a 

 square metre of meadow land yields on dry distillation a 

 quantity of ammonia corresponding to 223*3 grammes of 



Kew Eruptive C^ne within the Crater cf Vetuv.us, vhxh opeLtd on November 2, i£7S, and is still actlva. 



chloride of ammonium." Palmieri, while he admits that 

 he has found more chloride of ammonium in those por- 

 tions of lavas which have passed over cultivated ground, 

 asserts that he has also found it high upon Vesuvius far 

 above the range of vegetation, and in localities where the 

 new lava has simply flowed over older and perfectly 

 barren lava fields. He accounts for its formation by 

 supposing that aqueous vapour undergoes dissociation in 

 the heated crevices of the lava, and that the nascent 

 hydrogen combines with the nitrogen of the air to form 

 ammonia. We do not know what chemists will have to 

 say to this theory. 



Not far from the active cone I found a very interesting 

 specimen of volcanic cinder which had obviously been 

 exposed to the action of hydrochloric acid at a very elevated 

 temperature, and had then probably been ejected before the 

 action was complete. The central portions consisted of 

 undecomposed cinder, and this was surrounded by a thick 

 layer of perfectly white decomposed substance consisting 



chiefly of silicate of alumina and silica ; the hot hydro- 

 chloric acid having formed sesquichloride of iron with 

 the iron in the superficial layers of the mass, which 

 sesquichloride had been afterwaids volatilised out of the 

 mass. By passing hydrochloric acid over lava heated to 

 redness in a porcelain tube, the same effect was pro- 

 duced, the portions of lava most strongly heated, and 

 longest submitted to the action of the hydrochloric acid, 

 became perfectly white, while a copious sublimate of 

 chloride of iron and chloride of aluminium passed into 

 the receiver. 



I ascended from the new lava (viz., from the bottom of 

 the great crater of Vesuvius, 7n'(fe the foreground of the 

 accompanying woodcut) at 1.30 P.M., ran down the sides 

 of the great cone, which had taken fifty-five minutes to 

 climb, in seven minutes, reached the observatory at 

 2.30 P.M. ; Portici, by a roundabout way to the west near 

 Monte Somma, whither we went to search for minerals, 

 at 4.30 P.M.; and Naples at 5.40. ,The next evening 



