BABBAGE, Charles (1791-1871). 'Observations on the Notation Employed in the Calculus of Functions.' Offprint from: Transactions of the Cambridge Philosophical Society. Cambridge: printed by J. Smith, 1820. – 'On some new methods of investigating the sums of several classes of infinite series.' Offprint from: Philosophical Transactions. London: printed by W. Bulmer [for the Royal Society], 1819 – 'Observations on the analogy which subsists between the calculus of functions and other branches of analysis.' Offprint from: Philosophical Transactions. London: printed by W. Bulmer [for the Royal Society], 1817 – 'On a new zenith micrometer.' ?Offprint from: Memoirs of the Astronomical Society. London: 1825. Together 4 works bound in one volume, 4° (272 x 215mm). Large folding engraved plate to accompanying last named work. (Long clean tear to title of first named work, crudely repaired with tape, occasional faint spotting.) 20th-century wrappers (worn, covers detached). Provenance: AUTHORIAL PRESENTATION INSCRIPTION (on title of last named work, to:) – Joseph-Nicolas Nicollet – Georgetown College (stamps). RARE BABBAGE OFFPRINTS, ONE OF THEM WITH A SPLENDID REPUBLIC OF LETTERS ASSOCIATION. Joseph-Nicolas Nicollet (1786-1843) was a French geographer, astronomer, and mathematician best known for mapping the Upper Mississippi River basin during the 1830s. Prior to this, Nicollet had been a member of the French equivalent of the Board of Longitude, and Babbage and Herschel visited him during their joint tour of France in 1824. The offprint being presented here regards accurate measurement of 'minute portions of angular space' and would have been of considerable interest to Nicollet.