Dr. Walker on Ice Observations. 437 



authors have found that these oxides undergo no sensible increase of 

 weight, even after the destruction of 50 or 60 milligrammes of ozone. 

 The same oxides, when brought into contact with oxygen contracted 

 by the spark, restore it to nearly its original volume. 



Hydrogen gas, purified with care, and perfectly dry, was not 

 changed in volume by the action either of the electrical spark, or of 

 the silent discharge. 



_ A similar negative result was'obtained with nitrogen and the silent 

 discharge ; but with the spark a very slight alteration of volume 

 appeared to occur, the cause of which is still under investigation. 



In the experiments now described, the electrical sparks and dis- 

 charge were always obtained from the common friction-machine. 

 The discharge from the induction coil, even when passed through two 

 Leyden jars, produces very insignificant ozone effects. The heat 

 which always accompanies this discharge, and its comparatively feeble 

 tension, sufficiently explain its want of energy. 



All the results recently obtained by the authors fully confirm the 

 former experiments of one of them*, that in no case is water pro- 

 duced by the destruction of ozone, whether prepared by electrolysis 

 or by the electrical discharge. They reserve any further expression 

 of their views as to the true relations which exist between ozone and 

 oxygen, till they shall have an opportunity of laying the results of 

 this inquiry in a more complete form before the Society. 



"Ice Observations." By David Walker, M.D., Surgeon and 

 Naturalist to the Arctic Discovery Expedition. 



The contradictory statements of Dr. Sutherland and Dr. Kane, with 

 regard to the saltness of the ice formed from sea-water, — the former 

 maintaining that sea-water ice contains about one-fourth of the salt 

 of the original water; the latter, that if the cold be sufficiently 

 intense, there will be formed from sea-water a fresh and purer ele- 

 rnent fit for domestic use, — induced the author to take advantage of 

 his position, as naturalist to the expedition now in the northern seas, 

 to reinvestigate the subject. 



The changes which he has observed sea-water to undergo in 

 freezing are the following. When the temperature falls below 

 -|-28°'.5, it becomes covered with a thin pellicle of ice; after some 

 time this pellicle becomes thicker and presents a vertically striated 

 structure, similar to that of the ordinary cakes of sal-ammoniac. 

 As the ice further increases in thickness, it becomes more compact, 

 but the lowest portion still retains the striated structure. On the 

 surface of the ice, saline crystals, designated by the author " efflo- 

 rescence," soon begin to form, at first few in number and widely 

 separated, but gradually forming into tufts and ultimately covering 

 the whole surface. At first, the increase in thickness of the ice is 

 rapid, but afterwards the rate of growth is much slower and more 

 uniform. The ice formed yields, on being melted, a solution differ- 

 ing in specific gravity according to the temperature at the time of 



* riiilosopliical Transactions for 1856, Part I. 



