1835.] First Astronoinej:- Royal. 339 



it showed a method of finding the sun's true parallax (by 

 observations of the moon's dichotomy) which I was very 

 desirous of investigating at that time. But more of this 

 hereafter. I spent some part of my time in astrological 

 studies, but so as my labours were rather astronomical. 

 Amongst others I spent some time on Mr. Linacre's and 

 another great person's schemes ; yet could I not anyways 

 satisfy myself in the arcs of directions for the measuring of 

 time, nor am I yet perfectly satisfied. Yet I think Kepler's 

 measures most rational and best grounded ; though in the 

 great person's nativity which I directed I used Naboyd's 

 measure, which is most in use amongst astrologers. In 

 fine, I found astrology to give generally strong conjectural 

 hints not perfect declarations. 



Healthful, and in these studies, I spent the summer [of] 

 1^66. And now, August 19th, 1666, 1 was aged just twenty 

 years, whence I begin a perfecter account of myself. After I 

 had received Riccioli's^Zwzo^e^^ I set myself to read him when 

 an intermission from my father's business happened ; which 

 usually did at night in winter ; and I took much pleasure 

 in him. I found he differed from Tycho in the places and 

 distances of the fixed stars sometimes 4'. His obliquity 

 of the ecliptic, Riccioli confirms by his own observations : 

 to which and the sun's parallax deposed by him I shall say 

 more in my astronomical works. 



Thus I held on till December the 6th, when I found my- 

 self much pained with the headache and some other dis- 

 tempers ; which after a while reduced me to my usual win- 

 ter weakness and left me as ill as formerly. I continued 

 afflicted with a small pain and some grudgings of the head- 

 ache for a month after, so that I ended the year 1666 and 

 began 1666-7 with it. 



I transcribed some things from Riccioli, and taking occa- 

 sion to peruse his method of finding the sun's distance by 

 the moon's dichotomy, 1 could not but observe how he 

 introduced an arc for correcting the apparent dichotomy 

 and reducing it to the true which cannot be admitted. For 

 he supposes the moon's parallax to cause her to appear 

 hollow at the dichotomy next succeeding the new moon, 

 and more than half full at [the] dichotomy preceding the 

 change ; which I shall note to be so in my astronomical 



z2 



