EXPEDITION TOWARD THE NORTH POLE. 379 



tense cold slionld be studied on potassium, sodium, and otlier substances, 

 esi)ecially in relation to tlieir oxidation. 



The melting point of mercury should be observed, particularly- as a 

 means of correcting- the graduation of thermometers at low temperatures. 

 The resistance to freezing of minute drops of mercury, as has been 

 stated, should be tested. 



Facts long observed, when studied under new conditions, scarcely 

 ever fail to yield new and interesting results. 



JosErn UenFvY. 



NATURAL HISTORY. 



Objects of natural history of all kinds should be collected, and in as 

 large numbers as possible. For this purpose all on board the vessel, 

 both officers and sailors, should be reijuired to collect, upon every favor- 

 able opportunity, and to deliver the specimens obtained to those ap- 

 pointed to have charge of them. 



Zoology. — Tlie terrestrial mammals of Greenland are pretty well known, 

 but it is still desirable that a series, as complete as possible, of the skins 

 should be preserved, great care being taken to always indicate upon the 

 label to be attached the sex, and probable age, as well as the locality 

 and date of capture. The skeleton, and, when it is not possible to get 

 this complete, any detached bones, particularly the skull and attached 

 cervical vertebrae, are very desirable. Interesting soft parts, especially 

 the brain, and also embryos, are very important. If it should be con- 

 sidered necessary to record measurements, they should be taken from 

 specimens recently killed. 



Of walruses and seals, there should be collected as many skeletons as 

 l^ossible, of old and young individuals; also skins, especially of the seals. 

 Notes should be made regarding the habits in general, food, period of 

 copulation, duration of gestation and time of migration, it being desira- 

 ble to find out whether their migrations are periodical. 



Of the Cetacca, when these are too large to be taken on board the 

 vessel, the skull and cervical vertebra), the bones of the extremities and 

 penis, and whatever else may be deemed worthy of preservation, should 

 be secured. All the animals should be examined for ecto and ento par- 

 asites, and the means by which they become affixed to the animals 

 noted. 



Collect carefully the species of Myodcs {IcmmingsJ Arctomys and Arri- 

 cola, so as to determine the variations with locality and season. The 

 relationship of two kinds of foxes, the blue and white, should be studied 

 to determine their specific or other relationship. Any brown bears 

 should be carefully collected, both skin and skeleton, to determine 

 whether identical or not with the Old World Ursus arctos. 



Iieference has already been made to the seals and cetaceans ; of these 

 the Flioca cristata, the white whale, f Beluga, J and the Monodod are par- 

 ticularly desired. 



