TOL. XI.] PHILOSOPHICAL TRANSACTIONS. 333 



the 28th day of the same month, it must have returned nearly to the same 

 situation, had it still existed, in the night following the 25th of July; as is 

 deduced both from its velocity, the observed time of its appearance, and also 

 from the course of the other spots, which we have seen to finish their period 

 about the sun in 1T\ or 1T\ days. Besides, its path is different from the pre- 

 ceding ; for the former was something more remote from the equator of the 

 spots, than the latter. And this, if it should have consistence enough, should 

 return to the middle of the sun on Sept. 5, in the morning. 



From the scheme of the appearance of Saturn, as observed by M. Hevelius a 

 year ago, I perceive that he made use of telescopes much inferior to our's. For 

 at that time, and now also (Aug. 1676), in the globe of Saturn we observed an 

 obscure zone, a little south of the centre, not unlike the zones of Jupiter. Then 

 the breadth of the annul us was divided into parts, by an obscure line, apparently 

 elliptical, but in reality circular, as it were into two concentric rings, the interior 

 of which was brighter than the exterior. This phasis I saw immediately after 

 the emersion of Saturn from the sun's rays, through the whole year, quite to his 

 immersion ; first with a telescope of 35 feet, and afterwards with a less^ of 20 

 feet. See fig. 1^ pi. xi. 



An Intimation given in the Journal des Sgavans, of a sure and easy way to make 

 all sorts of large Telescopical Glasses ; with a generous offer of furnishing 

 industrious Astronomers with them gratis. By M. Borelli. N° 128^ p. 69 1. 



Mons. Borelli, a member of the Royal Academy of Sciences of Paris, whose 

 love for natural philosophy, and chiefly chemistry, has been long known, has 

 found out a sure and very easy method of working all sorts of large telescopical 

 glasses. He has already carried the experience of his secret to great extent, 

 having made one of them very good of 200 feet, wrought on both sides on the 

 same rule: which shows, that if he had wrought it flat on both sides, the glass 

 would have been of 400 feet. 



This easiness of making large glasses, and the desire of procuring some ad- 

 vancement to astronomical discoveries, have induced him to make presents of 

 them in divers places to several persons capable of using them : and the same 

 motive induces him to make the like offer, not only to the astronomers that are 

 dispersed up and down in the kingdom of France, but also to those that are in 

 foreign countries, especially in those parts, where there is some established 

 academy or society for astronomical observations ; offering in this case, to every 

 one of such societies, three very good glasses, one of 10 or 12 feet for a cham- 

 ber: another of 25 or 30 feet for ordinary observations, and a third of 60 or 80 

 feet for making new discoveries. 



