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diftance.. Though the columns of both thefe hills are 
of the fimple, or unjointed fpecies, Corneus cryjlallifatus 
prifmaticus lateribus inordinatis^ wallerii, yet they dif- 
fer very remarkably from each other in many refpecfts ; 
but principally in their forms, and the texture and qua- 
lity of their parts. Thofe of San Giovanni commonly ap- 
proach a circular form, as nearly as their angles will per- 
mit ; which is alfo obfervable in the columns of the Gi- 
ants Gaufeway, and of moft other bafaltine groups. On 
the contrary, thofe of Monte Roflb rather alFe(5t an ob- 
long or o\ dl figure, as may be more particularly obferv- 
ed in the annexed reprefentation of one of them <'^>’. The 
columns of San Giovanni meafure, one with the other, 
near a foot in diameter ; nor do they vary much in their 
fize; though this is often the cafe in fimilar groups, 
and is particularly obfervable in that of Monte RoflTo, 
whofe columns fometimes equal nearly a foot in diame- 
ter, while others fcarcely exceed three inches : the com- 
mon width of them is about fix or eight inches. They 
differ, therefore, very confiderably in fize from thofe of 
the Giants Gaufeway; fome of which, as is well known, 
meafure two feet in width. I can fay nothing certain 
concerning the length of the columns of San Giovanni, 
fince they prefent only their tops to view ; the remaining 
parts of them being deeply buried in the hill, and in fome 
places intirely covered, as may be feen in the drawing. 
The columns of Monte Roffo, as far as they are vifible, 
meafure only from fix to eight or ten feet in height; 
(a) Fig. 1, 
which 
