Editing Pytheas (section)

== Encounter with drift ice ==
[[File:Islossning (119329313).jpg|thumb|[[Pancake ice]] in the Baltic in spring near the [[Sweden|Swedish]] coast.]]
After mentioning the crossing (''navigatio'') from ''Berrice'' to ''Tyle'', [[Pliny the Elder|Pliny]] made a brief statement that:
<blockquote>
''A Tyle unius diei navigatione mare concretum a nonnullis Cronium appellatur'' . [One day's sail from Thule is the frozen ocean, called by some the Cronian Sea.]</blockquote>

The ''mare concretum'' appears to match Strabo's ''pepēguia thalatta'' and is probably the same as the ''topoi'' ("places") mentioned in Strabo's apparent description of spring drift ice, which would have stopped his voyage further north and was for him the ultimate limit of the world. Strabo says:<ref name=straboII-4-1 /><ref>Translation from {{harvnb|Chevallier|1984}}.</ref>

<blockquote>
Pytheas also spoke of the waters around Thule and of those places where land properly speaking no longer exists, nor sea nor air, but a mixture of these things, like a "marine lung", in which it was said that earth and water and all things are in suspension as if this something was a link between all these elements, on which one can neither walk nor sail.
</blockquote>

The term used for "marine lung" (''pleumōn thalattios'') appears to refer to [[jellyfish]] of the type the ancients called sea-lung. The latter are mentioned by [[Aristotle]] in ''On the Parts of Animals'' as being free-floating and insensate.<ref>IV.5.</ref> They are not further identifiable from what Aristotle says but some ''pulmones'' appear in Pliny as a class of insensate sea animal;<ref>''Natural History'' [https://www.perseus.tufts.edu/hopper/text?doc=Plin.+Nat.+9.71&fromdoc=Perseus%3Atext%3A1999.02.0137 IX.71].</ref> specifically the ''halipleumon'' ("salt-water lung").<ref>''Natural History'' [https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D32%3Achapter%3D32 XXXII.32].</ref> William Ogle, a major translator and annotator of Aristotle, attributes the name sea-lung to the lung-like expansion and contraction of the [[Jellyfish|Medusae]], a kind of [[Cnidaria]], during locomotion.<ref>{{cite book|page=[https://archive.org/details/aristotleonparts00arisrich/page/226 226]|author=Aristotle|author2=William Ogle |title=On the Parts of Animals|publisher=Kegan, Paul, French & Co | location=London | date=1882 | url=https://archive.org/details/aristotleonparts00arisrich|quote=On the Parts of Animals.}}</ref> The ice resembled floating circles in the water. The modern English term for this phenomenon is [[pancake ice]].

The association of Pytheas' observations with [[drift ice]] has long been standard in navigational literature, including [[Bowditch's American Practical Navigator|Nathaniel Bowditch's ''American Practical Navigator'']], which begins Chapter 33, ''Ice Navigation'', with Pytheas.<ref>{{cite book|title=The American Practical Navigator: an Epitome of Navigation|first=Nathaniel|last=Bowditch|author-link=Nathaniel Bowditch|publisher=National Geospatial-Intelligence Agency |date=2002 | edition=Bicentennial  |url=http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-34.pdf |access-date=7 June 2012}}</ref> At its edge, sea, [[slush]], and [[ice]] mix, surrounded by [[fog]].