at Berlin again. My friends pursued their theological studies with
earnestness, and I my natural science; therefore, at first we came
little into contact with one another.

So passed several months, when suddenly life threw us closer together
again. This came about through the call to arms in 1815. We all enlisted
again together as volunteers. On account of our previous service, and by
royal favour, we were at once promoted to officer's rank, and each one
was appointed to a regiment. However, there was such a throng of
volunteers that it was not necessary for any State officials to be
called upon to leave their posts, or for students to interrupt their
studies, and we therefore received counter-orders commanding us to stay
at home. Middendorff, who felt sure of his speedy departure for the
army, preferred not to take lodgings for the short time of his stay in
Berlin, and as there was room enough in mine for us both, he came and
stayed with me. Yet we still seemed to draw very little closer together
at first, because of the diversity of our pursuits; but soon a bond of
union wove itself again, which was all the stronger on that very
account. Langethal and Middendorff had endeavoured to secure a
sufficiency for their support at the university by taking private
tutorships in families, making such arrangements as that their
university studies should not be interfered with. In the beginning of
their work all seemed simple and easy, but they soon came upon
difficulties both as regards the teaching and the training of the
children entrusted to them. As our former conversations had so often
turned upon these very subjects they now came to me to consult me,
especially about mathematical teaching and arithmetic, and we set apart
two hours a week, in which I gave them instruction on these matters.
From this moment our mutual interchange of thought again became animated
and continuous.