114 Prof. Hansteen on the Number and Situation 
_. Further, The quantum of heat which would raise water to. 
1000, would elevate an equal bulk of glass to 2000. Hence 
we may infer, that from every snow there is received twice as 
much caloric as would be yielded by an equal depth of red-" 
hot powdered glass. 
- It is thus that the turbulent wave, which at one moment 
rocks the mariner’s sea-boat on the border of the torrid zone, 
transformed into a cloud, and borne away towards the arctic, 
soon after supports the sledge or the snow-shoe of an Esqui- 
maux or Greenlander; successively cooling or warming the 
surrounding media, by absorbing or giving out the material 
cause of heat. 
XIX. On the Number and Situation of the Magnetic Poles of 
the Earth. By Professor CuristopHER HansTEEN *. 
(PRE attraction of iron by the magnet was known to the 
naturalists of Greece and Rome, but it is uncertain at 
what time the Europeans became acquainted with that remark- 
able property of the magnet which we call Polarity; distinct 
traces, however, of the use of the compass are found towards 
the end of the twelfth century. There is no doubt that the 
Chinese knew it long before, and it is very probable that the 
Venetians obtained some information respecting it while 
trading on the Red Sea. 
Our Northern ancestors were in this respect not behind the 
inhabitants of Southern Europe, as may be seen in the Land- 
namabok, part i. chap. 2 and 7, where we are told that the 
famous Viking Floke Vilgerdarson, the third discoverer of 
Iceland, who sailed about the year 868 from Rogaland in 
Norway, in order to seek for Gardarsholm (Iceland), took 
three ravens with him, which were to serve him as guides. 
For on letting birds fly on the open sea, and finding them to 
return, it was considered:as a sign of there being no land near. 
But if they flew away, the vessel followed them, with a view 
of reaching the nearest shore. In order to consecrate these 
ravens for his purpose, Floke offered up a great sacrifice at 
Smiérsund, where the ships lay ready for sailing ; for “ at that 
time the navigators in the Northern countries had no magnets ” 
(pviat pa hifdo hafsiglingarmen enger leidarstein i pan pima & 
nordorlindim). As the Landnamabok was apparently written at 
* From Dr. Keemttz’s translation into German of the original memoir, 
published in the Magazin for Naturvidenskaberne, udgivet af Professorer ne 
Lundh, Hansteen og Maschmann, vol. i. p. 1—46. 
the 
