PHYSICAL PROPERTIES OF ICE. 637 



action, independent of percolation, solar heat, depending position, 

 or even depth of ice, produce from salt water a fresh, pure, and 

 drinkable element." 



2. Ice Observations. By Sir Edward Belcher. 

 The Formation of Floe-Ice. (Sir Edward Belcher.) 



Some interesting experiments were made on the rate and 

 mode of formation of the floe or salt-water ice by inserting a 

 wooden tube, with two opposite sides partially open, into the ice. 

 The results from November to March, recorded on page 123, 

 Vol. I. show an average increase of ice of half an inch a day 

 solely from below. Observations of thickness were made every 

 10 days, and compared with the recorded temperatures. 



After the ice-gauge was raised in March 1854, observations 

 were made on the in-shore ice to discover when the ice-crystals 

 ceased to attach themselves to the under surface. From Novem- 

 ber 5th to March 25th the thickness had increased from 18 to 

 68 inches. 



Again on April 9th (p. 161) the thickness of the ice was found 

 to be 66 inches. The ice had not only ceased to form, but the 

 lower portion of two inches in depth was entirely composed of 

 loosely cohering separate crystals yielding easily to the pressure 

 of the finger. The ice in contact with these crystals was also in 

 a rotten state. 



By experiments made by rapidly lowering bottles fitted with a 

 plug of loose cotton to a considerable depth so as to bring up 

 vvater from that depth, the water was found to be full of 

 crystalline stars of ice. 



These results entirely agreed v/itli experiments made on sea- 

 water in glass cylinders at 50° F., and submitted to a temperature 

 of — 24° F. The crystallization commenced from below. As the 

 freezing point was approached, peculiar stars were produced, and 

 rose to the surface where they became attached to and formed the 

 general mass. These stars were perfect detached crystals, similar 

 to those met with in the atmosphere. 



Experiments are also described in Vol. I. (p. 150) intended to 

 measure the amount of evaporation from ice, and cubes of ice 

 from different layers were exposed to the upper- deck temperature 

 during winter, and weighed at intervals to determine the changes. 

 The water which thawed from these cubes was bottled for future 

 examination, and the atmospheric air in well-dried bottles, and 

 covered with leather and bladder, was also obtained. 



In the Appendix at the end of Vol. 11. of the Last of the Arctic 

 Voyages will be found records of experiments to ascertain the 

 amount of evaporation from cubes of salt-water ice from different 

 depths in the floe ; also an Analysis of the Water, and a most 

 interesting Account of Observations on the Forms of and Changes 

 in Crystals of Ice and Snow, with magnificent pictures of the 

 remarkable and, in some cases, complicated forms which were 

 observed. 



