so INtRODUCTIOK. 



matical or cylindrical form, which is to be put into a 

 vessel, filled with sea- water : the length of the piece 

 immersed, compared with that of the part above 

 the water, gives the proportion in which the visible 

 mass of ice must be magnified, in order to obtain 

 the probable amount of the whole. Faithful draw- 

 ings of such ice-bergs, which have been formed, by 

 masses of ice piled upon, each other, are also de- 

 sirable, as well as measurements of the thickness 

 of flakes of ice, which seem to have been produced 

 by a single frost. We have already spoken of the 

 areometrical experiments in the vicinity of the 

 new-formed ice. As the meritorious naturalist, 

 Higgins, and, in these latter times. Parrot, induced 

 by experiments on a small scale, have disputed the 

 assertion of navigators, from Forbisher and Davis 

 down to the time of Cook, that the sea-ice con- 

 tains no salt, a new investigation of this subject on 

 the spot is desirable, which may be made by taking 

 a sufficient quantity of solid sea-ice, and, after 

 washing it, melting it in fresh water, and then 

 examining the specific gravity with the areometer. 

 To obtain further certainty, it might be proper to 

 fill some bottles with such ice, that the water may 

 be chemically analysed. 



Lastly, the external visible properties of the sea- 

 water, merit the attention of the navigator : its 

 colour, its transparency, and then the shining of 

 the sea at night. With regard to the first, it is to 

 be observed, how far the visible or altered colour 



