First visit to the Staatsbibliothek at Unter den Linden.
The Library consisted of two buildings (in different locations),
and so far I went only to the one at the Potsdamer Straße.
My purpose is to consult a textbook of mechanics written by Ch. Wolff.
Although the revised version is today available by its facsimile edition,
I've not seen the first edition (probably no copy is in Japan).
To my surprising, there are more differences between two editions
than I expected. Since I'm mainly interested in the first edition,
these differences are highly important.
I'm intend to visit once more the Library in this week.