When quietly on the march, both walking and tobogganing produce the same rate of progression, so that the string of arriving birds, tailing out in a long line as far as the horizon, appears as a well-ordered procession. I walked out a mile or so along this line, standing for some time watching it tail past me and taking the photographs with which I have illustrated the scene. Most of the little creatures seemed much out of breath, their wheezy respiration being distinctly heard. First would pass a string of them walking, then a dozen or so tobogganing. (Fig. 15.) Suddenly those that walked would flop on to their breasts and start tobogganing, and conversely strings of tobogganers would as suddenly pop up on to their feet and start walking. In this way they relieved the monotony of their march, and gave periodical rest to different groups of muscles and nerve-centres. The surface of the snow on the sea-ice varied continually, and over any very smooth patches the pedestrians almost invariably started to toboggan, whilst over "bad going" they all had perforce to walk. Figs. 16, 17, 18 and 19 present some idea of the procession of these thousands on thousands of penguins as day after day they passed into the rookery. [Illustration: Fig. 15. ON THE MARCH TO THE ROOKERY OVER THE SEA-ICE. SOME ARE WALKING AND SOME "TOBOGGANING" (Page 28)] When tobogganing, turning to one side or the other is done with one or more strokes of the opposite flipper. When fleeing or chasing, both flippers as well as both feet are used in propulsion, and over most surfaces tobogganing is thus their fastest mode of progression, but when going at full tilt it is also the most exhausting, and after a short spurt in this way they invariably return to the walking position. By October 20 many of the nests were complete, and the hens sat in them, though no eggs were to be seen yet. In the middle of one of the frozen lakes rose a little island, well suited for nesting except for the fact that later in the season, probably about the time when the young chicks were hatched, the lake would be thawed and the approach to the island only to be accomplished through about six inches or more of dirty water and ooze. Until then, however, the surface of the lake would remain frozen, and was at this time covered with snow. Not a penguin attempted to build its nest on this island, though many passed it or walked over it in crossing the lake. How did they realize that later on they would get dirty every time they journeyed to or from the spot? Not far from this island another mound rose from the lake, but this was connected with the "mainland" by a narrow neck of guano-covered pebbles. This mound was covered with nests, showing that the birds understood this place could always be reached over dry land. Surely this was well worth remarking.