of the Arctic Regions. 5287 
tion and detail. The 3d chapter is entitled Hydrographic Sui% 
vey of the Greenland Sea The author first assigns the 
limits of that portion of the ocean which he names the Green- 
land Sea, and then enters into all the details of the colour it as^ 
sumes in different places, of its various qualities, its specific 
gravity, and its degree of saltness. 
He notices the temperature of water drawn from different 
depths, the degree of pressure which it there sustains, and de- 
scribes an instrument which enabled him to make experiments 
on these latter subjects. The chapter concludes with some high- 
ly interesting remarks on the rapidity and direction of currents 
in general. The author extends his researches to a summary 
abstract of what is known on the formation of waves, on the 
causes of their greater or less elevation, and on the effects which 
they produce, when several billows coming in different direc- 
tions meet in the same place. 
The 4th chapter, of nearly 100 pages, is a complete and 
well arranged treatise on the Ices of the Greenland and Polar 
Seas in general. 
The author, in the first place, endeavours to fix definite ideas 
to the terms employed by seamen to designate the different 
forms assumed by the ice, with which the Polar Seas are often 
encumbered, and sometimes wholly covered ; whether the mas- 
ses of ice, connected together, present the aspect of a continuous 
plain, or the image of a country bristled with hills ; whether 
they consist of detached pieces in continual motion, that threa- 
ten by their collision to crush to pieces the ships entangled 
among them, or impinging against them, or, whether, reduced 
to smaller pieces, they form a barrier, through which it is not 
always safe to force a passage. 
The precision of the author’s descriptions greatly contributes, 
to tlirow a clear light on what he afterwards says of the forma- 
tion of the different kinds of ice, of the causes which collect 
tliem into masses of prodigious extent, or which shiver them 
into minute fragments. The isolated mountains of ice resem- 
bling floating islands, are also the subject of his researches. 
The author, in any of his descriptions, however alluring 
* The learned reporters have here erred ; they say, “ De&cripti<m des eauci^ ^ 
de la merd* ^ 
