A Letter to Dr. Halley, Astron. Reg. & F. R. S. Relating to a Surprising Shoal of Pumice-Stones Found Floating on the Sea, by Mr. John Dove

any notable Pressure, and that the *Sacculus* does not divide into *Coats* as the Artery from whence it arises does, I am induced to think that this Aneurysm is a Tumor form'd by the Blood's being forced thro' the ligamentous, or what is called the Muscular-coat, and distending the membranous or outer one. And because the Impetus of the Blood will, as it were, perpetually press thro' the Aperture into the Tumor, and be again (at least in Part) return'd by the Elasticity of the external Coat; therefore such a Tumor will rather have a *pulsatile* Dilatation, than a *Pulsation*, for its true Diagnostick. --- VI. A Letter to Dr. Halley, Astron. Reg. & F.R.S. relating to a surprising Shoal of Pumice-Stones found floating on the Sea, by Mr. John Dove. *SIR,* Having examined my Journal, I send you herein a particular Account of what I can remember, concerning the *Pumice-stones* we fell in with, in our Voyage to India in the *Lyell*, Charles Small Commander. On Monday the 22^nd of March, 1724, at Noon, being in the Latitude 35°, 36' South, and Longitude 4°, 9' West, with Variation 3°, 16', W. we discovered several *Pumice-stones* on the Sea; but not expecting any such thing thing at that Distance from the Land, (the Islands Tristan d'Acunha being the nearest, which I judged to bear from us W. 9°, 10', S. Distance 186 Leagues) we were in Dispute what it might be; when about 1 P.M. we took up a Piece in a Bucket, (the Ship going then but 3 Knots) which confirmed my Opinion of its being Pumice-stones, such as I gave you. Towards Night it was spread all round us as far as we could see: The Wind being variable from N. by E. to E. we stood to the Eastward: Towards Morning, the Wind veering to the Northward, we steered E.S.E. The Pumice-stones were very thick, in Drifts, lying N.N.E. and S.S.W. and extended out of our Sight at the Mast's Head, encreasing as we ran to the Eastward. To the 23rd at Noon I made our Course S. 38°, 30' E. Distance 76 Miles: Latitude by Observation 36°, 35' S. Longitude 3°, 24' West, from the Meridian of London. Wednesday the 24th, clear Weather and fresh Gales, variable from N.E. by N. to N. by W. with a long Swell from the Eastward. We continued our Course E.S.E. 140 Miles, the Pumice-stones being thicker; so that from Yesterday Noon till four this Morning, some of the Drifts were about a Cable's Length broad, and so thick, we could scarce see the Water between them; and there was much the same Breadth between the Drifts, with several Pumice-stones interspersed. Towards Noon, I found the Pumice somewhat thinner: Latitude 37°, 35' S. and Longitude 1°, 4' W. Thursday the 25th, from Noon till two this Morning, had a fresh Gale at N. and N.by E. afterwards little Wind from W. to N.W. with a N.E. Sea: we steered E.by S. 101 Miles. In the Evening the Drifts were near as large as above, but towards Morning decreased much; much; so that about Noon we were clear of these Pumice-stones, several of which were as big as a Man's Head. We have sailed 317 Miles since we first discovered them. They lay just in the Track for Ships outward bound, and we have no Account of them before; but all the Ships that went out the same Year, and since, (who go so far to the Southward) have fallen in with them. In the Morning we tried the Current, but found none: and no Ground at 130 Fathoms. At Noon Latitude 37°, 54' S. Longitude 0°, 38' E. The following Evening Variation 6°, 12' W. At Noon, I judge Tristan d'Acunha then bore from us W. 3°, 39' N. Distance 256 Leagues, supposing it to lie in Latitude 37°, 5' S. and Longitude 15°, 38' W. As to the Original of the Pumice-stones, I submit that to your better Judgment. If I can oblige you in any thing else, you may command, SIR, Your most humble Servant, East-Lane, Rotherbith, Febr. 27th. 1727-8. John Dove. VII. Some