616 Reviews — The Arctic Manual. 



Under the head of Miscellaneous Observations are some valuable 

 remarks and suggestions by Dr. Eae and Professor Tyndall. The 

 former deals with the salinity of ice, and the kinds which are most 

 useful as a source of water-supply for drinking purposes, and 

 points out that it is possible to procure " almost always " good 

 drinking water from "wasted old ice," which must not be con- 

 founded with " rotten ice," as the latter is spongy, comparatively 

 thin, saline, and unsafe to travel on, while the former breaks into 

 detached floes when quite thick and solid. This rotten ice is worn 

 away whilst in situ by sea-currents acting on its under surface ; 

 while the upper, owing to the low temperature of the air, is not 

 affected ; but it was suggested by Dr. E. Brown that this alteration 

 may further be due to the accumulation of Diatomaceas below the 

 surface, which would tend to increase the local heat and be there- 

 fore perhaps another cause of the phenomenon to which Dr. Eae 

 refers. Be the cause what it may, the fact itself is of considerable 

 importance when the water-supply in an ice-bound region fails, and 

 the determination of that kind of ice whence good water could be 

 obtained is not merely interesting, but might be of considerable 

 utility to those vessels which frequent the Northern seas. 



Professor Tyndall's remarks, suggested by his own laborious re- 

 searches, call especial attention to the formation of snow crystals and 

 the rapidity of the conduction of heat through ice, and the action of 

 the great Arctic glaciers. It is still a disputed point whether the 

 icebergs are formed by the uplifting action of the water when the 

 ice mass projects into the sea, in which case the surface being in a 

 state of longitudinal compression, and therefore devoid of crevasses, 

 or by the gravity of the overhanging end, when such fissures must 

 naturally be formed. Some suggestive remarks on the method of 

 determining the range of sound conclude the paper, to which Prof. 

 Tyndall has appended copies of his valuable papers on the " Physical 

 Properties of Ice," the "Atmosphere as a Vehicle of Sound," and 

 " Forms of Water," which will doubtless furnish many important 

 hints to those who accompany the Expedition. 



Part II. of the first section of the book is devoted to Biology 

 (Zoology and Botany), and Geology and Mineralogy. The first 

 portion is purely for guidance in collecting the Mammalia, Birds, 

 Fishes, Crustacea, Mollusca, Polyzoa, Hydroids, etc. ; and for 

 the determination of the more important varieties careful lucid 

 descriptions are given ; while the various points of interest about 

 which our knowledge is still imperfect are fully noted. The com- 

 pleteness of this section, as a guide to, perhaps in some instances, 

 inexperienced collectors, is very noticeable ; and its value is en- 

 hanced by a brief but pertinent paper by Professor Huxley, calling 

 particular attention to Microscopic collections of various kinds, but 

 particularly those which could lead to a comparison between the 

 microscopic Fauna and Flora of the surface-waters of the sea and 

 those of the sea-bottom, to be obtained by dredging from the same 

 localities. 



The botanical section, by Dr. J. Dalton Hooker, consists of but 



