311 



the given temperature ; and, if the same vacuum be filled with air, though just 

 the same amount of watery vapour would rise if the temperature is kept the 

 same, yet it would take a considerable time. It follows, therefore, that the 

 difFusibility of watery vapour is rendered much more rapid when the pressure 

 of the air is reduced by its upward oscillations ; it is taken more rapidly into 

 the cold upper regions where it is condensed. It may be interesting to note 

 the experiments of Dulong, which show that " equal volumes of all gaseous 

 fluids, at the same tempei-ature and pressure, on being suddenly compressed or 

 dilated to any equal volumes, disengage or absorb the same amount of heat, 

 and the amount of heat required to raise a gas to a certain temperature 

 increases the more it is allowed to expand. If there be no source of heat from 

 which this additional supply can be obtained, the gas is cooled." And there 

 does not appear to be this source of heat in the highest i"egions of the atmos- 

 phere, where the air is rare, for its diathermancy if dry, as we must suppose it 

 to be in these regions, allows of the transmission of the heat rays of the sun 

 through it, no heat is absorbed by it, therefore none can be radiated, and we 

 have already seen that terrestrial radiation is much diminished by passing 

 upwards through the aqueous vapour near the earth's surface. 



Referring once moi'e to the miniature column of the atmosphere contained 

 in the glass tube, if the air be heated it will expand, and if cooled it will 

 contract, and conversely (from what Faraday terms " the Correlation of 

 Physical Forces ") ; if it be mechanically compressed, its temperature rises, and 

 if rarefied its temperature lowers. With suitable apparatus, the column could 

 be made to show not only a reduction of temperature when mechanically 

 expanded, but also a loss of transparency arising from partial condensation of 

 its watery vapour. 



Aet. LVIII. — Notes on the Chatham Islands and their Inhabitants. 



By Gilbert Mair. 



[Read before the Wellington Philosophical Society, November 12, 1870.] 



The Chatham Islanders, or Morioris, or, more correctly, Maiorioris, state that 

 they came to the Chathams in five canoes, viz : — Rangitane, Rangihona, Rangi- 

 mata, RuapuJie, and Okahu. They say that they came from the villages of 

 Tahurimanuka and Wharepapa, at Hawai, whence they were driven by tribal 

 qnan-els ; that upon their arrival at the Chathams they found the islands 

 thickly populated by natives, differing very considerably from themselves. 



There wei^e two tribes of them, — the Rongomaitere and the Rongomai- 

 whenua. At first, and for some years aftei', they had numerous fights with 

 these people, but chey eventually made peace with each other, and by inter- 

 marriages became as one people. 



