378 EXPEDITION TOWARD THE NORTH POLE. 



like meridians, and converging to a point in the eastern horizon. Any 

 appearance of this kind shoukl be carefully noted and described. 



Meteors. — Shooting-stars and meteors of all kinds should be observed 

 with the spectroscope. The direction and length of their motion should 

 be traced on star-maps, and especial attention should be given at 

 the stated periods in August and November. A remarkable disturb- 

 ance of the aurora has been seen during the passage of a meteor 

 through its beams. Any phenomenon of this kind should be minutely 

 described. 



Ozone. — The expedition is furnished with a quantity of ozone test 

 paper, observations with which can only be rendered comparable by pro- 

 jecting against the sensitized paper a given quantity of atmospheric 

 air. For this purpose an aspirator should be nsed, which may be made 

 by fastening together two small casks, one of whicli is filled with water,- 

 with their axes parallel, by means of a piece of plank nailed across the 

 heads, through the middle of which is passed an iron axis on which the 

 two casks may be made to revolve, and the full cask may readily be 

 placed above the empty, so that its contents may gradually descend 

 into the latter. During the running of the water from the upper 

 cask, an equal quantity of air is drawn through a small adjutage 

 into a closed vessel, and made to impinge upon the test-paper. The 

 vessel containing the test-paper should be united with the aspirator by 

 means of an India-rubber tube. 



Miscellaneous. — The conduction of sound during still weather, through 

 the air over the ice, through the ice itself, and through the water, may 

 be studied. 



Evaporation of snow, ice, and water may be measured by a balance, 

 of which the pan is of a given dimension. 



Experiments on the resistance of water to freezing in a confined space 

 at a low temperature, may be made with small bomb-shells closed with 

 screw-plugs of iron. The fact of the liquidity of the water at a very low 

 temperature may be determined by the percussion of a small iron bullet, 

 or by simply inverting the shell, when the ball, if the liquid remains 

 unfrozen, will be found at the lowest point. It might be better, how- 

 ever, to employ vessels of wrought iron especially prepared for the pur- 

 pose, since tlie porosity of cast-iron is such that the water will be forced 

 through the pores, e. g., the lower end of a gun-barrel, which, from the 

 smallness of its diameter, will sustain an immense pressure, and through 

 which the percussion of the inclosed bullet may be more readily heard. 

 Water, in a thin metallic vessel, exposed on all sides to the cold, some- 

 times gives rise to hollow crystals of a remarkable shape and size, pro- 

 jecting above the level surface of the water, and exhibits phenomena 

 worthy of study. 



Exi)erimeuts may be made on regelation, the plasticity of ice, the con- 

 solidation of snow into ice, the expansion of ice, its. conducting power 

 for heat, and the various forms of its crystallization. The eflect of in- 



