Pliny.
The next authority is Pliny (nat. A.D. 23, ob. A.D. 79), who makes Thule the northernmost British island. Both he and Cæsar (Bell. Gall., v. 13), placing Mona about N. lat. 66°, declare that the sun does not set in summer, but perpetually disappears during the winter solstice. To the former phase Cæsar assigns thirty days, Pliny six months (senis mensibus). The great natural philosopher mentions the Massilian traveller without abusing him:
“Pytheas informs us that this is the case (i.e., the day lasting six months, and the night being of equal length) in the island of Thule, which is six days’ sail from the north of Britain” (Nat. Hist., vol. i., book ii., chap. 77, Bostock and Riley, Bohn, 1835).
In book iv., chap. 30, occurs:
“The most remote of all that we find mentioned is Thule, in which, as we have previously stated, there is no night at the summer solstice, when the sun is passing through the sign of Cancer; while, on the other hand, at the winter solstice there is no day.”
Again (loc. cit.):
“There are writers also who make mention of some other islands, Scandia, namely, Damna, Bergos, and, greater than all, Nerigos (or Nerigo, Noreg, i.e., Norway), from which persons embark for Thule. At one day’s sail from Thule, is the Frozen Ocean, which by some is called the Cronian Sea.”
Finally, in book vi., chap. 39, we find:
“The last of all is the Scythian parallel,[10] which runs from the Riphæan range to Thule, in which, as we have already stated, the year is divided into days and nights alternately of six months’ duration.”
With these passages before us, it is easy to understand why popular writers generally assume Pliny’s Thule to be the Shetland Isles. But he evidently confirms the account of Pytheas, and adds the significant detail about the Cronian or Frozen Sea. It is well established that the ocean south of Iceland is not icy, whilst the northern and western shores are often frost-bound.