(530 PHILOSOPHICAL TRANSACTIONS. [aNNO I7II. 



shew us any more likely theory, for my part I shall be ready to consent to you 

 in any thing with reason. 



" Thus you have, what for the present, I conceive of these maculae solares. 

 Fromundus mentions one Jo. Tarde Gall us, who thinks them to be secondary 

 planets ; who hath written a book of that subject, and calls them astra borbonia: 

 but I could never yet see it. What you, or he, or others may alledge for that 

 opinion, I know not. In the mean time it were too much levity in me, against 

 my judgment, to acknowledge them stars; unless I see at least some possibility 

 how they may be so, or some probability why they should not rather be spots. 

 Which when you, or they, do produce from better grounded reasons, optical 

 experiments, or demonstrations, I shall willingly recant my opinion. 

 '" " In the mean time, let me encourage you to proceed in your noble optical 

 speculations. I do believe there are as rare inventions as Galilaeus' Telescope, 

 yet undiscovered. My living in a place void of apt materials for that purpose, 

 makes me almost ignorant in those secrets; only what I have from reason, or 

 the reading of Kepler's Astron. Opt. and Galilaeus. If you impart unto us any 

 of your optical secrets, we shall be thankful, and obliged to you, and ready to 

 requite you in any thing we can. 



" It is true which you say, that I found Venus' diameter much less than any 

 theory extant made it. Kepler came nearest, yet makes her diameter 5 times 

 too much. Tycho, Lansberg, and the ancients, about 10 times greater than 

 it was. So also they differ in the time of the ^ as far from the truth. By 

 Lansberg the c5 should have been l6^ 3]' before we observed it; by Tycho and 

 Longomontane l*^ 8^ 25' before. By Kepler, who is still nearest the truth, 

 9^ 46' before. So that had not our own observations, and study, taught us a 

 better theory than any of these, we had never attended at that time for that 

 rare spectacle. You shall have the observation of it when we see you. The 

 clouds deprived me of part of the observation, but my friend and second self, 

 Mr. Jeremiah Horrox, being near Preston, observed it clearly from the time of 

 its coming into the sun, till the sun's setting; and both our observations agreed, 

 both in the time and diameter, most precisely. If I can, I will bring him along 

 with Mr. Towneley and myself to see Yorkshire and you. You shall also then 

 have my observation of the sun's last eclipse here in Broughton, Mr. Horrox's 

 between Liverpoole and Preston, and Mr. Foster's at London. Lansberg in 

 eclipses, especially of the ([ , comes often nearer the truth than Kepler, yet it 

 is by packing together errors; his diameters of the and (( being false, and 

 his variation of the shadow being quite repugnant to geometrical demonstration. 

 His circular hypotheses Mr. Horrox, before I could persuade him, assayed a 



