Phenomena ofFesuvius. 49 



the trunk of this pine, already much weakened from other cir- 

 cumstances, instead of the cylindrical column presented only a 

 series of large and small globes, which the authors attribute, in 

 great measure, to the enfeebled state of the electric attraction 

 of the air. At the conclusion of the eruption the volcano at- 

 tracted to itself all the clouds of the atmosphere, from which 

 was formed an immense quantity of water, which rolling down 

 its sides in torrents, and carrying with it large quantities of in- 

 coherent matter, devastated the surrounding country. Of the 

 pisolites, some of them, and those the largest, fell already 

 formed ; the others were formed upon the ashes which covered 

 the ground by means of a fine rain. 



Section 3d. " Observations and Experiments made during 

 the Eruption of October 1822." This section is the longest, 

 the most interesting, and contains the greatest variety of new 

 facts. The following are the titles of its principal divisions : 



Art. I. " Periods of the Maximum and Minimum of Violence 

 which this Eruption presented. In this is given in detail the 

 fact that the paroxysms appear subject to this general law, 

 that their violence is in the inverse ratio to their duration. The 

 shortest and most terrible are in the middle of the eruption ; 

 the longest and feeblest, at its commencement and at its 

 close. 



Art. II. " State of the Crater and of the great Cone on the 

 16th of November 1822. — Description of the Cone and of the 

 actual Crater." The Atrio became more and more filled up, 

 and Vesuvius, properly so called, and Mount Somma were ap- 

 proaching to union. The edge of the crater in question was 

 very narrow. 



The authors have given in this part a review of the obser- 

 vations made upon the height of Vesuvius from the year 

 1749 to 1822. 



Art. III. " Examination of the Substances which are 

 ejected or produced during the Eruption." These are di- 

 vided into five classes: 1. incoherent solids; 2. liquids; 3. 

 volatile substances; 4. gaseous substances; 5. imponderable 

 substances. Each of these classes is examined separately 

 and in detail, and the various modes and periods of their ap- 

 pearance are pointed out. The ashes have been carried as far 

 as 105 miles in almost all directions; and the strata which are 

 the result of them, as well as those consisting of other incohe- 

 rent matter, are studied under various aspects, and are ob- 

 served to differ greatly from those formed by alluvial deposi- 

 tion. The effects of these showers of ashes on organized 

 bodies are again spoken of. The currents of lava form sub- 



Vol. 63. No. 309. Jan. 1824. G jects 



