[ 93 ] 
§ .i4* i-'Iiere is alfo another worm, which padcs 
thro’ the coral tranfverfely from fide to fide, and in 
rig it lines, by drait cylindrical holes. 
It may not be improper to take notice here, that 
the harded marbles, lying in the fea, are liable to be 
corroded in the lame manner. 
§ 15. The furface of the fubdance of coral is fur- 
rowed and wrinkled (Pig*. B. Fig. D. e, z/,). The 
wrinkles begin from the foot, and afcend, always 
nearly parallel, to the trunk and branches. However, 
thefe wrinkles are not fo deep in the llender branches, 
and fometimes are not vifible there : but they are al- 
ways more elevated, and more confiderable, in the 
thick branches and trunk : they are not fmooth, but 
uneven, with knobs or bumps on them, and the fur- 
face, as it were, compofed of very little hemifpheres. 
§ 16. This fubdance of the coral, being expofed 
to a drong lire, is reduced to a very fine adi- colour’d 
powder. As common adies, when taken clean from 
burning charcoal, and examined by a microfcope, 
exhibit a fort of fkeleton, compofed of the fibres 
and vedels of the wood; fo the allies of the fub- 
dance of coral diffidently point out, of what fort of 
parts it is compofed. The microfcope difcovers 
therein adies, formed of very lmall white corpufcles, 
united in cluders ; each one of which is nearly lplie- 
rical. The allies of the bark of the coral are of the 
fame diape and colour ; fo that the fubdance of coral 
agrees with its bark in the primitive and condituent 
parts (if I may be allow’d the expreifion) which 
feem to be the lame in both. 
§ 17. In pieces of coral broken tranfverfely, I 
have often obferved fome prominent wrinkles, which, 
difengaging 
