VOL. LXXXIII.] PHILOSOPHICAL TRANSACTIONS. 299 



auricle ; c the posterior ventricle, which is usually inclined to the left side ; d the posterior auricle ; 

 E the superior vena cava ; f the aorta ; g the pulmonary artery 5 h the common trunk of the left 

 carotid, and subclavian arteries ; i the right carotid ; k the right subclavian ; l the hepatic vein ; 

 M part of the diaphragm ; n the liver ; o the superior mesenteric artery ; p the renal artery ; q the 

 renal vein ; r the vena cava inferior ; s tlie aorta continued ; tt the vena portarura. 



In fig. 4, A is the anterior auricle, turned backwards, that the vena cava may be seen ; b the 

 posterior ventricle ; c the posterior auricle ; d the superior vena cava ; e the inferior vena cava ; f the 

 conjoined veins passing beneath the basis of the heart to the anterior auricle ; g the beginning of 

 the vessels of the right lung ; h the pulmonary artery ; i the aorta ; k the hepatic vein ; l part of 

 the diaphragm ; m the liver ; n tlie coeliac artery ; o the hepatic artery ; p the splenic artery ; q 

 the renal artery ; r the superior mesenteric artery ; s the renal vein ; tt the vena portarum. 



X, An Account of the Equatorial Instrument. By Sir George Shuckburgh, 



Bart.F.R.S. p. 67. 



The first account, that I meet with, says Sir G. of an astronomical instrument 

 that bears any resemblance to this, is to be found in Ptolemy, (lib. 5 of his Al- 

 magest) with which he says he determined the distance between the 2 tropics. 

 This instrument is described under the name aa-TjoXaSixon o^yavov, and appears to 

 have consisted of 2 circles, placed at right angles to each other, one representing 

 the meridian or solsticial colure, and the other the zodiac ; the former turning 

 on an axis, placed parallel to the axis of the earth, being elevated to the latitude 

 of the place, and the other turning within it on 2 centres, removed 23°i from 

 the former axis ; and was in truth not very unlike the common ring dial, only 

 about 6 times as large. Each circle was divided into 360°, and those again into 

 3 or 4 subdivisions ; and being furnished, it may be supposed, with moveable 

 sights, the observer was enabled to take the elevation or depression of any object 

 above or below the ecliptic, together with its distance from the meridian, or 

 colure, that circle being previously placed parallel to its corresponding one in the 

 heavens. The first measure would give the latitude of any heavenly body, and 

 the latter the longitude. This instrument, or something similar to it, seems to 

 have been in use as early as the time of Hipparchus, who lived in the 2d century 

 before our Saviour, (vide Weidleri Hist. Astron. p. SIQ; et Tychonis Brahe 

 Mechanica) and was continued to be used by astronomers for upwards of ] 5 cen- 

 turies afterwards. 



The next account that occurs is by J. Muller, Regiomontanus, sive Joannes 

 de Monte Regio, who flourished about a. 0. 1460, and, in a posthumous treatise 

 expressly on this subject, entitled Scripta clarissimi Mathematici M. Joannis 

 Regiomontani de Torqueto, Astrolabio armillari, Regula magna Ptolemaica, 

 Baculoque Astronomico, &c. &c. in quarto, printed at Nuremberg in 1544, has 

 given a pretty full account, not only of the armillary astrolabe, but also of the 

 torquetum, which in fact was nothing more than a portable equatorial, and may 

 be considered as the first instrument truly of this kind. As this treatise is become 



QQ 2 



