After the Peace of Paris he settled down for a time to a quiet life in the mineralogical museum at the University of Berlin, his duties being the care, arrangement, and investigation of crystals. Surrounded thus by the exquisite formations whose development according to law is so perfect, whose obedience to the promptings of an inward ideal so complete, he could not but learn from their unconscious ethics to look into the depths of his own nature, and there recognize more clearly the purpose it was intended to work out. In 1816 he quietly gave up his position, and taking as pupils five of his nephews, three of whom were fatherless, he entered upon his life work, the first step in which was the carrying out of his plan for a "Universal German Educational Institute." He was without money, of course, as he had always been and always would be,--his hands were made for giving, not for getting; he slept in a barn on a wisp of straw while arranging for his first school at Griesheim; but outward things were so little real to him in comparison with the life of the spirit, that bodily privations seemed scarcely worth considering. The school at Keilhau, to which he soon removed, the institutions later established in Wartensee and Willisau, the orphanage in Burgdorf, all were most successful educationally, but, it is hardly necessary to say, were never a source of profit to their head and founder. Through the twenty succeeding years, busy as he was in teaching, in lecturing, in writing, he was constantly shadowed by dissatisfaction with the foundation upon which he was building. A nebulous idea for the betterment of things was floating before him; but it was not until 1836 that it appeared to his eyes as a "definite truth." This definite truth, the discovery of his old age, was of course the kindergarten; and from this time until the end, all other work was laid aside, and his entire strength given to the consummate flower of his educational thought. The first kindergarten was opened in 1837 at Blankenburg (where a memorial school is now conducted), and in 1850 the institution at Marienthal for the training of kindergartners was founded, Froebel remaining at its head until his death two years after. With the exception of that remarkable book 'The Education of Man' (1826), his most important literary work was done after 1836; 'Pedagogics of the Kindergarten,' the first great European contribution to the subject of child-study, appearing from 1837 to 1840 in the form of separate essays, and the 'Mutter-und-Kose Lieder' (Mother-Play) in 1843. Many of his educational aphorisms and occasional speeches were preserved by his great disciple the Baroness von Marenholtz-Buelow in her 'Reminiscences of Froebel'; and though two most interesting volumes of his correspondence have been published, there remain a number of letters, as well as essays and educational sketches, not yet rendered into English.