Michelsen, Johann Andreas Christian. Letters about the initial reasons of the letter calculus and algebra. XXXVI, 3 Bl. Content, 598 pp., 1 Bl. (print error). 18 x 10.5 cm. Brown cardboard band d. Zt. with RSchild (something rubbed and toasted). Berlin, S.F. Hesse, 1789. See Poggendorff II, 147. ADB XXI, 698. – Title edition of the edition of 1786, which can also be found in 1789 under the title "Instructions on letter calculus and algebra". Michelsen (1749-1797) was Professor of Mathematics and Physics at the Berlin grammar school "Zum Grauen Kloster" and dealt in 29 letters the mathematical signs, comparison of the rectangles, consideration of the quotients, potencies, fractures, equations, root pulling etc. – estate of Notarius Rose, gift of the chamberwife Henriette Rose (Exlibris); Grand Duke. Library Neustrelitz (Stamp verso title); Tholé (?; Name entry on title). Upper edge with slight water traces, about 15 leaves brown discoloured.