VOL. XXX.] PHILOSOPHICAL TRANSACTIONS* 323 



in Feb. l6gg, a third in April 1702, and again a fourth in Nov. 1707; none 

 of which, as far as I can learn, were ever seen in England; all of them having 

 been very obscure and without tails, by means of which comets usually first 

 show themselves. And besides these, two other comets, with remarkably long 

 tails, the one in Nov. 1689, the other in Feb. 1702, passed by unobservable 

 in these our northern climates, having great south latitude, and their motions 

 directed toward that pole. Hence we may justly conclude that the returns of 

 comets are much more frequent than is commonly reckoned, and that it is 

 only contingent, that for these 35 years no one of them has been seen and 

 observed by our astronomers. 



But there may be still a much greater number of these bodies, which by 

 reason of their smallness and distance are wholly invisible to the naked eye; so 

 that unless chance direct the telescope of a proper observer, almost to the very 

 points where they are, against which there are immense odds, it will not be 

 possible to discover them : and that this is not barely a conjecture, take the 

 following instance. 



On Monday, June 10, in the evening, the sky being very serene and calm, 

 I was desirous to take a view of the disk of Mars, then very near the earth, 

 and appearing very glorious, to see if I could distinguish by my 24-foot tele- 

 scope, the spots said to be seen on him. Directing my tube for that purpose, 

 I accidentally fell upon a small whitish appearance near the planet, resem- 

 bling in all respects such a nebula as I lately described in Phil. Trans. N° 347, 

 but smaller. It seemed to emit from its upper part a very short kind of radia- 

 tion, directed towards the east, but rather northerly; which, considering its 

 situation, was nearly towards the point opposite to the sun. The great light 

 of the moon, then very near it and also near the full, hindered this phenome- 

 non from being more distinctly seen ; but its place in the heavens was suffici- 

 ently ascertained from the vicinity of Mars, from which it was but about half 

 a degree distant towards the southwest, the difference of latitude being some- 

 what more than that of longitude; and Mars being at that time in I iy° 30', 

 with 3*^ 48' south latitude. I concluded its place about X 17^ 12', with 4° 12' 

 lat. south: which may yet be more securely determined by help of two small 

 fixed stars I found near it, the more northerly of which I judged to have the 

 same latitude with it, and to follow it at about the distance of 6 minutes; the 

 other star was about 4 minutes more southerly than the former, and about one 

 minute in consequence thereof; the angle at the northern star was a little 

 obtuse, as of about 100 degrees, and the distance of our nebula from it 

 sesquilateral to the distance of the two stars, or rather a little more. The 



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