644 PHYSICAL PROPERTIES OF ICE. 



snow is much lower than that of sea-water ice, the degree de- 

 pending upon the amount of salts contained. Consequentlj, in 

 these lanes does the disintegrating action first commence ; the 

 sun's rays acting on this mass, thaw it, and form a kind of sludge 

 on top ; afterwards exosmosis and endosmosis commence, the ice 

 acting as the membrane between the salt water below and the 

 sludgv pools above ; in time this intervening ice becomes per- 

 meated and infiltrated with salt, less buoyant, and thus soon 

 becomes a prey to the eroding action of the water and the thaw- 

 ing power of the sun. Thus the new lanes and bay-ice are first 

 broken up, allowing more play to the water on the remaining 

 thicker mass, and at the same time giving greater advantage to 

 the action of the wind, which drifts it to a warmer situation, 

 where it is soon reduced in bulk, and gradually Avastes away. But 

 not only do these lanes experience the effect of the efflorescence, 

 but also the main body of the floe, but not to so great an extent, 

 as there is more snow mixed with it, and the intervening mem- 

 brane is much thicker. The portions of the hummocks which 

 were below the general under surfiice of the floe having become 

 water-eaten, honej^combed, and detached, now make their appear- 

 ance (under the name of tongue-pieces), and act the part of 

 wedges, keeping ^.eparate the different fields and masses of ice. I 

 have said these tongue pieces are water-eaten and honeycombed. 

 The salts retained in the ice are not equally dispersed through it, 

 but are (if I might so speak) contained in cells, having aggregated 

 at the time of freezing ; as these cells are exposed to the thawing 

 power of the water beneath, they become melted much sooner than 

 the mass of the ice, less heat being required, and thus present the 

 honeycombed appearance seen by every one as they sail through 

 nips in the floe. The needle-ice spoken of by Parry and other 

 Arctic travellers over ice is due to the same cause, although that, 

 distinguished navigator says it depends on the drops of rain. I 

 have often seen it in early summer, before one drop of rain had 

 fallen, but when the sun had commenced to act on the surface of 

 the ice. 



A word or two on the appearances seen when sea-water was 

 frozen in a capacious vessel. After, say, 12 hours' exposure, 

 when the ice Avas removed, it was found vertically striated, and 

 oftentimes divisible into two or more layers, the under-surface 

 presenting a curious aspect, small lines of about half an inch long, 

 and in groups of four or six, reticulating, seemed to cover the 

 entire under-surface. 



This occurred at all temperatures, and independent of length of 

 exposure and consequent thickness of ice. From the bottom of 

 the vessel thin plates of ice were seen protruding into the resi- 

 duary watei', from -J to 2^ inches long, and proportionately wide. 

 These were found to be much fresher than the ice formed on top, 

 or the residue below ; they completely studded the bottom of the 

 vessel. The appearance of these plates was not at all modified by 

 the varied density of the residue in which they were formed, or 

 even the density of the primary solution ; but of course their 



