Details
A RARE 18TH-CENTURY LACQUERED-BRASS PARALLELAGRAM,
SIGNED ON THE PRIMARY RULE JONATHAN SISSON LONDON, THE RULE ENGRAVED WITH SCALE ON ONE SIDE, 1-12, BY PROGRESSION, THE OTHER SIDE 100-0, THE CENTRE RULE SIMILARLY ENGRAVED BUT WITH TWO SCALES 1-12 TO ONE SIDE OF THE RULE, THE OTHER SIDE ENGRAVED 100-0/100-0, THE THIRD RULE SIMILARLY ENGRAVED TO THE FIRST, THE CENTRE RULE ARRANGED SO AS TO SLIDE WITHIN TWO SQUARE-SECTION COLLETTS WITH IRON WING TIGHTENING SCREWS, THE TWO PARALLEL LINK ARMS JOINTED TO THE RULES WITH SCREWS AND SPACER WASHERS, ONE FITTED WITH IVORY CASTOR, ANOTHER WITH MOUNTING FOR SCRIBE, ANOTHER WITH MOUNTING FOR PEN, THE BALUSTER-TURNED CORNER SUPPORT WITH PLAIN TABLE CLOTH-COVERED LEAD WEIGHT, CONTAINED IN A MAHOGANY CASE -- 21½IN. (54.6CM.) WIDE; AND A PHOTOSTAT COPY OF AN ORIGINAL DRAWING AND DESCRIPTION OF THE PARALLELAGRAM
SEE ILLUSTRATION
SIGNED ON THE PRIMARY RULE JONATHAN SISSON LONDON, THE RULE ENGRAVED WITH SCALE ON ONE SIDE, 1-12, BY PROGRESSION, THE OTHER SIDE 100-0, THE CENTRE RULE SIMILARLY ENGRAVED BUT WITH TWO SCALES 1-12 TO ONE SIDE OF THE RULE, THE OTHER SIDE ENGRAVED 100-0/100-0, THE THIRD RULE SIMILARLY ENGRAVED TO THE FIRST, THE CENTRE RULE ARRANGED SO AS TO SLIDE WITHIN TWO SQUARE-SECTION COLLETTS WITH IRON WING TIGHTENING SCREWS, THE TWO PARALLEL LINK ARMS JOINTED TO THE RULES WITH SCREWS AND SPACER WASHERS, ONE FITTED WITH IVORY CASTOR, ANOTHER WITH MOUNTING FOR SCRIBE, ANOTHER WITH MOUNTING FOR PEN, THE BALUSTER-TURNED CORNER SUPPORT WITH PLAIN TABLE CLOTH-COVERED LEAD WEIGHT, CONTAINED IN A MAHOGANY CASE -- 21½IN. (54.6CM.) WIDE; AND A PHOTOSTAT COPY OF AN ORIGINAL DRAWING AND DESCRIPTION OF THE PARALLELAGRAM
SEE ILLUSTRATION