VOL. LX.] PHILOSOPHICAL TRAKSACTIONS. ftt' 



must be held in the direction mn. So here would be no aberration of the 

 vessel V. 



3. Suppose V to move the same way, but slower. A ball from v would now 

 be really carried forward, that is, to the right hand, though not so far as in the 

 second supposition ; and therefore would be left behind in respect of the vessel 

 E ; and so, would come to the side of the vessel somewhere between o and n ; but 

 the greater its velocity towards the right, the nearer to n. So that if the 

 velocity of v were to be continually increasing from nothing till it became equal 

 to that of E, "a tube to receive the ball must be held first in the direction om, 

 looking forward, and afterwards, more and more inclined till it came into the 

 perpendicular direction mn. Hence it is natural to conclude, 



4. That if v move the same way, but swifter, a tube to receive the ball must 

 be reclined backward. For the ball would now be carried to the right hand 

 further than in the 2d supposition ; and therefore would come to the other side 

 of the vessel at some point p on the right hand of n, as if it proceedetl from some 

 point a on the left hand of s. 



This last seems to be the case of the transit, by supposing s to be the sun, 

 E the earth, and v the planet Venus passing between them from left to right, 

 and with a greater velocity than the earth, greater nearly as 24 to 20. And it 

 should seem that the aberration must make Venus appear farther to the left 

 hand, or to the east from the sun, and consequently retard the transit, and make 

 it happen later than it would otherwise do. 



XXXI. On the Transit of Fienus, the Lengths of Pendulums, also the Inclination 



and Declination of the Magnetic Needle. By Mr. Mallett, of Geneva, in a 



Letter to Dr. Bevis, F. R. S., dated April 13, 1770. p. 363. 



I had the pleasure of writing you a few lines in August, last year, when I sent 



you my observations relative to the transit of Venus, which the Petersburg 



Academy has printed without my knowledge, while I was yet in Lapland. I 



left Russia soon afterwards, and have been 5 or 6 months in my own country. 



Part of this time I have employed in reducing and computing my observations 



made in the north, to get what useful results I could from them, which I have 



just now sent to Petersburg, to be printed in the Commentaries of the Academy. 



As it may be some time before that volume will be published, I thought. Sir, you 



might be willing to be informed of some of the principal consequences resulting 



from my observations. 



1°. To determine the latitude of Ponoi, where I observed the transit, a great 

 number of meridian altitudes of the stars and sun, taken with a quadrant of 2 

 feet radius, made at London by Mr. Sisson, gave the elevation of the pole 

 67° 4' 30". I was not able to make any other observation but that of the sun's 



