VOL. XV. I PHILOSOPHICAL TRANSACTIONS. 223 



grow cold ; when afterwards he came to look upon it, to see if what remained 

 might be of any use to him, he was surprized to find it variously and briskly 

 moved. Wherefore having set it aside, to he certain that it should be thoroughly 

 cold, he after some hours visited it again, and found it move as before. And 

 having cast a quantity of seeds upon it, to see if the liquor would move them 

 also, the bituminous part of it connected them into a kind of thick scum, that 

 covered most of the superficies; but yet left some intervals, in which the liquor 

 appeared, and discovered that it continued its motions. Two days after, the 

 engineer told me of this odd accident. And though it was then a dark night 

 and bad weather, my diffidence or my curiosity made me engage him to send 

 for the pot as it was ; partly to be sure of the matter of fact, and partly to try 

 if the knowledge I had of the ingredients, which he had before told me, would 

 afford any hint of the cause of so odd an effect; alike to which in kind, though 

 not in degree, I had many years before devised, and successfully practised, the 

 way of producing. 



The vessel being come, though the hasty transportation of it seemed to 

 have sufficiently disturbed it, there appeared manifest signs of such a motion, 

 as the engineer had ascribed to it ; and therefore having set it aside in a labora- 

 tory, where some furnaces kept the air constantly warm, and did there and 

 elsewhere, at distant times, look heedfully upon it, now and then displacing, 

 or quite taking off, some of the thick scum ; and by this means I had the op- 

 portunity to take notice of several phaenomena, whereof these are the chief. 



First I observed, that the motion of this liquor was not only brisk, but very 

 various ; so that having loosened some small portions of the scum from the 

 rest, one of them would be carried towards the right hand, for instance, and 

 another towards the left, at the same time. — 2. Where the liquor first came 

 out from under the scum, it seemed to move ihe most briskly, flowing almost 

 like a stream, whose motions upwards had been checked, and as it were rever- 

 berated, by that incumbent obstacle. — 3. Several motions in this liquor were 

 the more easy to be observed ; because though it were dark, yet it was not uni- 

 form, consisting in part of oily and bituminous ingredients, which though they 

 seemed to have but one common superficies with the rest of the liquor, yet by 

 their colours and power of vigorously reflecting the light, they were easily 

 enough distinguishable from the rest. And I often observed, that some of 

 these unctuous portions of the matter, emerging to the surface of the liquor, 

 though perhaps at first one of them would not appear larger than a pin's head; 

 yet in moving forwards it would at the same time diffuse itself circularly, and 

 make as it were a great halo, adorned with the colours of the rainbow, and so 

 very vivid, as afforded a very pleasant and surprizing spectacle; these phantasms 



