The monsoon was expected in about three weeks and the gorge would then be completely closed with floods so their exploration of the Sanctuary could only be brief. They had difficulty crossing the Rishi - at this point is the confluence of a northern and southern arm at a height of about . To the north the river emerges from a large glacier and it was in this direction they started their survey. They saw for the first time the vast northern face of Nanda Devi - an unbroken sweep of . They reached the rim of the northeastern encircling mountains at over and looked over to the east to the Milam Glacier hoping there might be an alternative way out of the Sanctuary. They also went to the northernmost part of the ring but while they were exploring the foothills of Changabang the weather deteriorated and the Sherpas effectively took the lead when both Europeans were ill. On 24 June the monsoon arrived and they started their retreat, urged on by the Sherpas. In heavy rain they descended the gorge to the Rhamani river in two days. This river had become torrential and they were forced upstream to where they found an easy crossing point and a route back to Dibrughita from where they raced back to civilisation. In a letter Shipton wrote of the Sanctuary There was a tremendous variety of birds and any amount of game - most of which can never have seen a man, and stared at us incredulously. I was glad we did not have guns - it would have been a crime to shoot them. It was perhaps the most wonderful three weeks of my life, and I shall never forget a moment of it...