Jan. 4, 1872] 



NATURE 



185 



Of the Suez Canal fauna we were able to observe 

 very little, except that the canal perfectly swarms with 

 fish from one end to the other. A good many were 

 taken with hand-lines in two spots, one close to Port 

 Said, the other in the middle of the Great Bitter Lake. 

 They were all of one species, a sort of mullet, but there 

 are no books at hand to determine llie species. The mud 

 brought up from the bottom of the Great Bitter Lake by 

 the chain cable was absolutely devoid of any traces of life. 

 The Miizaporc has been visited on her voyage by various 

 land birds. One hen chaffinch accompanied us from Cape 

 Finisterre to Port Said, not leaving the ship when she was 

 anchored at Malta, and was to be seen everyday hopping 

 about the deck and feeding. At present the ship is sur- 

 rounded by vast flights of flying fish. They fly generally 

 up wind, and sometimes go as far as one hundred yards. 



It is hoped that this short note may be found of some 

 interest, and that it will be borne in mind that it is im- 

 possible to travel about with a library suflkient to dcter- 

 niine species on the spot, 



H. N. MOSELEV 



MELTING AND RECELATION OF ICE 



AN observation made yesterday caused me to present to 

 my class, in a lecture on Heat this morning, the follow- 

 ing experiment. A piece of wire gauze was laid on a con- 

 venient horizontal ring, and on this a lump of ice. A 

 flat board was placed on the ice, and pressure was applied 

 by means of weights put upon the laoard. I put 12 lbs. 

 upon a piece of ice as large as an apple. This was done 

 at the commencement of the lecture, and before the con- 

 clusion I found a considerable quantity of ice on the lower 

 side of the gauze, apparently squeezed through the meshes. 

 The temperature of the class-room was about 15° C. 

 (59' Fah.). The experiment was continued for eight or 

 ten hours, fresh ice being suppUed when necessary to the 

 upper side of the gauze, and, in spite of the continual 

 surface melting and dripping away of water, a very 

 large quantity of ice was formed below the gauze. The 

 ice below the gauze was firmly united to that above. I 

 tried with my hands to break away the upper from the 

 lower, and to lireak either of them off at the place where 

 the wire gauze separated them ; but I was not able to do 

 so. The ice that has passed through the meshes has a 

 kind of texture corresponding to that of the network, and 

 the small air bubbles appeared to be arranged in columns. 



The phenomenon is a consequence of the properties, 

 announced from theory by Prof. James Thomson, and 

 then exemplified by an experiment ; and the explanation 

 depends on the theories put forward by him — the first 

 (1857) founded on the lowering of the freezing point of 

 water by pressure, and the second (1S61) founded on the 

 tendency to melt given by the application to the solid 

 ice of forces whose nature is /o produce cliangt of form 

 as distinguished from forces applied alike to the liquid 

 and solid. The stress upon the ice, due to its pressure 

 on the network, gives it a tendency to melt at the point 

 in contact with the wire, and the ice, in the form of water 

 intermixed with fragments and new crystals, moves so as to 

 relieve itself of pressure. As soon as any portion of the 

 mass is thus relieved, freezing takes place throughout it, 

 because its temperature is reduced below that of the 

 freezing point of water at ordinary pressures, by melting 

 of contiguous parts. The obvious tendency of the ice 

 under the pressure from above is thus, by a series of 

 meltings and refreezings, to force itself through the 

 meshes. 



The next experiment that 1 tried I was led to by 

 that just described. I supported a block of ice on 

 two parallel boards, placed near to each other, and 

 passed a loop of wire over the ice. The loop hung 

 down between the boards, and weights were attached 



to it. The first wire tried was a fine one (o'oo; inches 

 diameter) and a two-pound weight was hung on the loop. 

 The wire immediately entered the ice, and it passed right 

 through it and dropped down with the weiglit after having 

 done so, but it left the ice undivided, and on trying it with 

 a knife and chisel in the plane in which the cutting had 

 taken place, I did not find that it was weaker there than 

 elsewhere. The track of the wire was marked by opacity 

 of the ice along the plane of passage. This opacity 

 seemed to be due to the scattering of air from the small 

 bubbles cut across by the wire. 1 have not, however, 

 been able to try a piece of ice free from bubbles ; and, 

 from the nature of the experiment, air may very possibly 

 pass in along the Wire from the outside. 1 next e.x- 

 perimented with a wire o'o24 inches diameter, weight- 

 ing the loop with 8 lbs., and obtained a similar result ; 

 and, finally, I took a wire o'l inch diameter, and, putting 

 a 561b. weight on a loop of it, I caused it to pass through 

 the ice, and the block remained undivided. This, though 

 it follows from theory, has a most startling eft'ect ; and 

 during the passage of the thick wire through the ice, 

 I was able to see the bubbles of air across which it cut 

 rising up round its sides. I made careful trials to cut the 

 ice with a knife in the lamina through which the wire 

 had passed, but found no weakness there. 



A string was next tried, but, as might be expected, it 

 did not pass through the ice. I considered that the string 

 was not a good enough conductor to relieve itself of the 

 cold in front and pass it back to the water behind. The 

 capillary action of the string also doubtless takes part in 

 the production of the result. It simply indented the ice 

 and froze into it. 



On this point of the necessity for a good conductor, 

 and for a way of relieving itself of the cold, a curious 

 obser\ation was made. In one case a thick wire appeared 

 to have stopped (this requires confirmation) as if it were 

 frozen into the ice. On examination it turned out that the 

 ice was so placed that the water formed by the pressure of 

 the wire had flowed away at the first, and a hole was left 

 behind the wire. On supplying a few drops of water to 

 the place from a small pointed bit of melting ice, the 

 water froze instantly on coming in contact with the wire, 

 and the wire moved forward as usual. By this 1 was 

 also led to try putting a thick wire over a piece of ice 

 having a hollow at the top, so that the wire cutting into 

 the shoulders bridged across the hollow between them. 

 Looking at the wire, which was in front of a window, I 

 dropped some ice-cold water on it, and saw it freeze 

 inslantly into crystals on the parts of the wire near to the 

 shoulders on which it was pressing. This is notable as 

 the first experimental confirmation of Prof. Thomson's 

 theory on the production of cold by the application of 

 stress. 



I have not yet had an opportunity of trying these ex- 

 periments at a temperature lower than freezing. The 

 amount of pressure necessary to make the wire pass 

 through the ice would of course be very much increased 

 as the temperature is lowered, and it would finally be 

 impossible to cut the ice without breaking it up like any 

 other hard solid. Indeed 1 saw in one case in which I 

 had a very great weight (Solb. or so) on a thick wire, the 

 ice cracking in front of the wire ; apparently the wire 

 was forced too fast through the ice. 



These experiments seem to me to have considerable 

 importance in relation to the sliding motion of glaciers. 

 The smallness of the cause has been raised as an ob- 

 jection to the theory of Prof. Thomson. But no one can 

 see the experiments 1 have described, particularly the 

 first, where a large quanuty of ice is squeezed through 

 the meshes of fine wire gauze under small pressure and 

 in a short time, without feeling ahnost surprised at the 

 slowness of the glacier motion, 



James Thomson Bottomlev 



Glasgow University, Dec. 20, 1871 



