DRAWING INSTRUMENTS 5 



14. Recipient Angle or Semicircular Protractor. 



Radius 4 inches. Orrery Coll. (49 ?). 



Inscr. : I Rowley fecit. 



Semicircle graduated o-i8o in both directions. Fitted with ad- 

 justable rulers, marked Ext. and Inf., as in Stone's Bion, PI. XI, Fig. D. 

 This type of instrument was of great use for plotting fortifications. 



15. Circular Protractor. 



Diameter iaf inches. Christ Church. 



Inscr. : J. St'ssbn, London. 



Divided to f degrees. A very beautifully graduated instrument. 



16. g-inch Sector. 



Ivory, with silver hinge. Orrery Coll. jl^rlAT^ 



Inscr. I Rowley fecit. 



17. 6-inch Sector. c. 1720. 

 Ivory, with brass hinge. ? Orrery Coll. 

 Apparently by Rowley, but unmarked. 



18. 12-inch Sector. 



Brass, in deal box. Christ Church. 



19. 9 -inch Sliding Gunter. 



Ivory. Orrery Coll. 



Inscr. : I: Rowley, fee. 



20. io-inch Artillerist's Gunnery Scale. 



Ivory, with silver slider. Orrery Coll. 



Inscr. : I Rowley Fecit. 



Slide Rule. 



21. Oughtred's Circles of Proportion and Horizontal Instrument. 



1632. 



Diameter i foot 6 inches. St. John's College. 



This fine instrument is inscribed with the name of the maker, Elias 

 Allen fecit, and with the name of the donor 



GEORGIVS BARKHAM; FILIVS D. IOHANNIS 



COMMENSALIS; BARKHAM S. T. P. 



DONO DEDIT A 1635 

 (Coat of Arms) 



(Motto) RECTA CERTA 



Unfortunately all the movable parts but the base-plate and a couple of 

 thumb-screws are missing. 



The face of the instrument is engraved with Oughtred's Horizontal 

 Instrument. The back is engraved with eleven Circles of Proportion 



