But again his studies were interrupted, this time by the king of Prussia’s celebrated call “To my people.” Though not a Prussian, Froebel was heart and soul a German. He therefore responded to the call, enlisted in Lützow’s corps, and went through the campaign of 1813. His military ardour, however, did not take his mind off education. “Everywhere,” he writes, “as far as the fatigues I underwent allowed, I carried in my thoughts my future calling as educator; yes, even in the few engagements in which I had to take part. Even in these I could gather experience for the task I proposed to myself.” Froebel’s soldiering showed him the value of discipline and united action, how the individual belongs not to himself but to the whole body, and how the whole body supports the individual. Froebel was rewarded for his patriotism by the friendship of two men whose names will always be associated with his, Langethal and Middendorff. These young men, ten years younger than Froebel, became attached to him in the field, and were ever afterwards his devoted followers, sacrificing all their prospects in life for the sake of carrying out his ideas. § 7. At the peace of Fontainebleau (signed in May, 1814) Froebel returned to Berlin, and became curator of the Museum of Mineralogy under Professor Weiss. In accepting this appointment from the Government he seemed to turn aside from his work as educator; but if not teaching he was learning. The unity of nature and human nature seemed more and more to reveal itself to him. Of the days past in the museum he afterwards wrote: “Here was I at the central point of my life and strife, where inner working and law, where life, nature, and mathematics were united in the fixed crystaline form, where a world of symbols lay open to the inner eye.” Again he says: “The stones in my hand and under my eye became speaking forms. The world of crystals declared to me the life and laws of life of man, and in still but real and sensible speech taught the true life of humanity.” “Geology and crystallography not only opened for me a higher circle of knowledge and insight, but also showed me a higher goal for my inquiry, my speculation, and my endeavour. Nature and man now seemed to me mutually to explain each other through all their numberless various stages of development. Man, as I saw, receives from a knowledge of natural objects, even because of their immense deep-seated diversity, a foundation for and a guidance towards a knowledge of himself and life, and a preparation for the manifestation of that knowledge” (_Autob._ _ut supra_, p. 97). More and more the thought possessed him that the one thing needful for man was unity of development, perfect evolution in accordance with the laws of his being, such evolution as science discovers in the other organisms of nature.