136 PHILOSOPHICAL TRANSACTIONS. [aNNO ]685. 



more luminous. On June 30, new style, l684, I first saw the comet, when 

 its place was in libra, 9° some minutes, with 8° + north latitude. The first 

 17 days of July, its places by observation, were as below. 



The last 4 observations may require some better calculation, as an error of some 

 minutes seems to have crept in. The observation on the 1st of July is very 

 exact; for the comet appeared in the telescope along with the star in virgo 

 marked il by Bayer, and fell under the girdle of the first northern part. But 

 the most certain observation of all, is that on the 6th day, when arcturus was 

 seen through the telescope along with the comet. Also, on the 14th day, the 

 comet and the star p^ in the hunting pole of Bootes, under his shoulder, were 

 seen at one view in the telescope. 



Observations on boiling Fountains and Subterraneous Steams. By Dr. Tancred 

 Robinson, F. R. S. N° 169, p. 922. 



The water of the noted boiling fountain at Peroul, near Montpelier, is ob- 

 served to heave and boil up very furiously in small bubbles; which manifestly 

 proceed from a vapour breaking out of the earth, and rushing through the 

 water, so as to throw it up with noise, and in many bubbles; for upon digging 

 any where near the ditch, and pouring other water on the dry place newly dug, 

 the same boiling is immediately observed. The like bubbling of water is also 

 found round about Peroul on the sea shore, and in the Etang itself. In order 

 to discover the cause of this odd phenomenon. Dr. Robinson took some of the 

 sand and earth out of the fountain and ditch, putting it into vessels, and pour- 

 ing some of the same water upon it, there did not appear the least commotion 

 or alteration; the surface of the water continuing very smooth, equal, and 

 quiet. On further search, he discovered in several dry places of the ground 

 thereabouts, many small venti-ducts, passages, or clefts, where the steam issued 

 forth ; at the mouths of these pipes, placing some light bodies, as feathers, small 



