In the following July we find him again upon the glacier. But the campaign of 1843 opened sadly for the glacial party. Arriving at Meiringen they heard that Jacob Leuthold was ill and would probably be unable to accompany them. They went to his house, and found him, indeed, the ghost of his former self, apparently in a rapid decline. Nevertheless, he welcomed them gladly to his humble home, and would have kept them for some refreshment. Fearing to fatigue him, however, they stayed but a few moments. As they left, one of the party pointed to the mountains, adding a hope that he might soon join them. His eyes filled with tears; it was his only answer, and he died three days later. He was but thirty-seven years of age, and at that time the most intrepid and the most intelligent of the Oberland guides. His death was felt as a personal grief by the band of workers whose steps he had for years guided over the most difficult Alpine passes. The summer's work continued and completed that of the last season. On leaving the glacier the year before they had marked a network of loose boulders, such as travel with the ice, and also a number of fixed points in the valley walls, comparing and registering their distance from each other. They had also sunk a line of stakes across the glacier. The change in the relative position of the two sets of signals and the curve in their line of stakes gave them, self-recorded, as it were, the rate of advance of the glacier as a whole, and also the comparative rate of progression in its different parts. Great pains was also taken during the summer to measure the advance in every twenty-four hours, as well as to compare the diurnal with the nocturnal movement, and to ascertain the amount of surface waste. The season was an unfavorable one, beginning so late and continuing so cold that the period of work was shortened. CHAPTER 12. 1843-1846: AGE 36-39. Completion of Fossil Fishes. Followed by Fossil Fishes of the Old Red Sandstone. Review of the Later Work. Identification of Fishes by the Skull. Renewed Correspondence with Prince Canino about Journey to the United States. Change of Plan owing to the Interest of the King of Prussia in the Expedition. Correspondence between Professor Sedgwick and Agassiz on Development Theory. Final Scientific Work in Neuchatel and Paris. Publication of "Systeme Glaciaire." Short Stay in England. Farewell Letter from Humboldt. Sails for United States.