218 PHILOSOPHICAL TRANSACTIONS. [aNNO 1668. 



to find, that the same motion which was made from south to north in the in- 

 ferior part of the disk, was on the contrary made from north to south in the 

 superior part. The next day at sun rising, the bright part was not far from the 

 section, and distant from the southern horn -i- of the diameter. When the sun 

 was 4 deg. high, the same was situated near the section, and remote from the 

 southern horn ^ of the diameter. The sun being 6^ lO' high, it seemed to 

 have passed the centre, and that the section of the disk intersected it. The 

 sun being 7 ° high, it appeared yet more advanced northward, together with 

 two obscure spots seated between the section and the circumference, and 

 equally distant from one another, and from each horn on both sides. And the 

 sky being very clear, he observed the motion of the bright part for 1^ hour; 

 which then seemed to be exactly made from south to north, without any sen- 

 sible inclination east or westward. 



May 10 and 13, before sun rising, he still saw the bright part near the 

 centre northward. Lastly, June 5 and 6, before sun rising, he saw the 

 same between the northern horn and the centre of the planet, and noted the 

 same irregular variation in the obscure spots. But when Venus began to be 

 further removed from the earth, it was more difficult to observe these phaeno- 

 mena. 



These appearances in Venus being seen for so small a time, makes it very 

 difficult to know with certainty when they return to the same place. Yet 

 this I can say, supposing that this bright part of Venus which I have observed, 

 especially this year 1667, has been always the same ; that in less than one day it 

 completes its motion, whether of revolution or libration, so as in near 23 hours 

 it returns about the same hour to the same situation in this planet ; but yet not 

 without some irregularity.* 



Extract of a Letter written hy Dr. J. Denis t of Paris, touching a late 

 Cure of an inveterate Phreiuy hy the Transfusion of Blood ; tran- 

 slated from the original French, Addressed to the Editor, Mr. 

 Oldenburg. N" 32, p. 6I7. 



You have doubtless heard of a madman that has been lately cured and re- 

 stored to his understanding by means of transfusion. Some spread a rumour 

 that he died soon after the operation ; others that he was relapsed into a greater 

 madness than before ; and in short it has been so differently spoken of that I 



* From these observations, though rather imperfect, Cassini deduced a conclusion pretty near the 

 truth 5 more modern and accurate observations having shewn that the period of Venus's rotation is 

 completed in 23 h. 22 m. 



