But we now knew one or two things about that pressure which we had not known twenty-four hours ago; for instance, that there was a lot of alteration since the Discovery days and that probably the pressure was bigger.  As a matter of fact it has been since proved by photographs that the ridges now ran out three-quarters of a mile farther into the sea than they did ten years before.  We knew also that if we entered the pressure at the only place where the ice-cliffs came down to the level of the Barrier, as we did yesterday, we could neither penetrate to the rookery nor get in under the cliffs where formerly a possible way had been found.  There was only one other thing to do—­to go over the cliff.  And this was what we proposed to try and do.

Now these ice-cliffs are some two hundred feet high, and I felt uncomfortable, especially in the dark.  But as we came back the day before we had noticed at one place a break in the cliffs from which there hung a snow-drift.  It might be possible to get down that drift.

And so, all harnessed to the sledge, with Bill on a long lead out in front and Birdie and myself checking the sledge behind, we started down the slope which ended in the cliff, which of course we could not see.  We crossed a number of small crevasses, and soon we knew we must be nearly there.  Twice we crept up to the edge of the cliff with no success, and then we found the slope:  more, we got down it without great difficulty and it brought us out just where we wanted to be, between the land cliffs and the pressure.

[Illustration:  THE BARRIER PRESSURE AT CAPE CROZIER]

Then began the most exciting climb among the pressure that you can imagine.  At first very much as it was the day before—­pulling ourselves and one another up ridges, slithering down slopes, tumbling into and out of crevasses and holes of all sorts, we made our way along under the cliffs which rose higher and higher above us as we neared the black lava precipices which form Cape Crozier itself.  We straddled along the top of a snow ridge with a razor-backed edge, balancing the sledge between us as we wriggled:  on our right was a drop of great depth with crevasses at the bottom, on our left was a smaller drop also crevassed.  We crawled along, and I can tell you it was exciting work in the more than half darkness.  At the end was a series of slopes full of crevasses, and finally we got right in under the rock on to moraine, and here we had to leave the sledge.

We roped up, and started to worry along under the cliffs, which had now changed from ice to rock, and rose 800 feet above us.  The tumult of pressure which climbed against them showed no order here.  Four hundred miles of moving ice behind it had just tossed and twisted those giant ridges until Job himself would have lacked words to reproach their Maker.  We scrambled over and under, hanging on with our axes, and cutting steps where we could not find a foothold