386 PHILOSOPHICAL TKANSACTIONS. [aNNO I7I9. 



2 its articulation with the incus; 3 the incus; 4 the manubrium malleoli; 5 a point of the incus, 

 framed by the other two productions; 6 the long protuberance of the incus; 7 the sinus in the extre- 

 mity of its long production. 



Fig. 15, the malleolus, incus, and stapes, articulated together; 1 the incus; 2 the malleolus; 3 

 the stapes where it shuts the foramen ovale. 



Fig. 16 represents the upper part of the lineae semilunares, or that side which is towards the pas- 

 sage of the nervus auditorius; a the five extremities cut off; b the linea semilunaris major; c the 

 semilunaris media; d the minor; e the common canule between the major and media. 



Fig. 17 represents the cochlea and labyrinth together; a the vestibulum ; b the foramen ovale; 

 c the foramen oblongum ; d tlie linea semilunaris minor, which is towards the cavitas tympani j e the 

 common canule to the major and media; f the major; g the media; h the cochlea. 



Fig. 18 represents the cochlea; a the vestibulum ; b the third gyre or turning ; c the orifice; d 

 the first gyre or turning opened; e the second turning; g the orifice at the top of the cochlea. 



Observations of the Transit of the Body and Shadow of Jupiter's Fourth Sate/lite 

 over the Disks of the Planet. By the Rev. Mr. James Pound, F. R. S, 

 N^ 359, p. 900. 



Feb. 16, 1719, at 6^^, through a short tube, we saw all the four satellites, 

 the three outermost on the east side of Jupiter, and the innermost near the 

 western limb approaching to an eclipse. The fourth at that time was about half 

 a semidiameter of Jupiter from the eastern limb. It then proved cloudy till 

 about 8^, at which time, through the long glass, we could see only the second 

 and third satellites, the first being behind Jupiter in the shadow, and the fourth 

 entered on the disk. We saw at this time a dark spot, a little northward of 

 the great northern zone, and near the eastern limb, where the satellite was to 

 enter on the disk, which we took for the shadow of the satellite. The clouds 

 then again intercepted our view, till 8*^ 53*" mean time, when the first satellite 

 was lately emerged out of the shadow, and the spot advanced so far, that we 

 perceived it would arrive at the middle of Jupiter near 2 hours sooner than the 

 shadow ought to have done by our computation; but not imagining that this 

 dark spot could be any thing else but the shadow, we concluded there had been 

 some error in the calculation, which we thought to re-examine afterwards. On 

 this presumption we left oiF observing till 9^ 35™, at which time we were sur- 

 prised to see a notch in the limb of Jupiter, near the place where the former 

 spot entered. This last appearance agreeing well with the time that the shadow 

 of the satellite ought to have entered the disk, soon made us alter our former 

 opinion, and conjecture that this, and not the other spot, was the said shadow. 

 At 9*^ 39"™ the notch vanishing, a round black spot appeared within the limb, 

 but in contact with it. At 9*^ 45™ we judged the first spot, and at 1 1*^45™ the 

 second, to be in the middle of Jupiter. 



At 1 1'^ 50™ the first spot touched the limb, being within the disk ; soon after 



