(• 444 ) 
any notable Preflure, and that the Sacculus does not 
divide into Coats as the Artery from whence it arifes 
does , I am induced to think that this Aneuryfm is a 
Tumor form’d by the Blood’s being forced thro ’ the 
ligamentous , or what is called the Mufcular-coat, and 
diji ending the membranous or outer one. And be- 
caufe the Impetus of the Blood will, as it were, per- 
petually prefsthro’ the x^perture into the Tumor, and 
be again (at leaf! in Part) return’d by the Elafticity of 
the external Coat ; therefore fuch a Tumor will ra- 
ther have a pulfatile Dilatation, than a Tulfation , for 
its true Diagnoitick. 
vi. A Letter to Dr. Halley, AJI r on. ^(eg. 
p. relating to a furprijing Shoal of Pumice- 
Stones f omul floating on the Sea, by .Mr. John 
Dove. 
siflfc, 
H Aving examined my Journal, I fend you herein a 
particular Account of what I can remember, con- 
cerning the c Pumice-Jlones we fell in with, in our 
Voyage to India in the Lyell^ Charles Small Com- 
mander. 
On Monday the n d of March, 172?, at Noon, being 
in the Latitude 35 , 36' South, and Longitude 4 0 , 9' 
Weft, with Variation 3 0 , 16', W. wedifcovered feveral 
Tumice-Jtones on the Sea } but not expe&ing any fuch 
thing 
