VOL. XIV.] PHILOSOPHICAL TRANSACTIONS. 101 



Now that there may be such a bitumen or inexhaustible oil, I need carry you 

 no farther than Pitchford, in Shropshire, where there is a naphta or liquid bitu- 

 men, that constantly issues forth with a spring there, and floats on the water; 

 this might be separated before it joins the water into a duct of its own, and so 

 conveyed to some place convenient for such a lamp, into which it should as 

 perpetually distill as it does now into the fountain ; and thus we have an oil as 

 everlasting as our wick, nor need we fear any extinction if inclosed in a tomb 

 or vault under ground, in however damp or moist a place; it being the charac- 

 teristic of a bitumen, to burn best where there is moisture, as is evident upon 

 affusion of water upon sea-coal. And this is one way in which we might have 

 a perpetual lamp, and that even without a wick, as the bitumen will burn with- 

 out it, when once lighted. All the objection I can foresee that is likely to ob- 

 tain against such an experiment, is that such a lamp as this would as likely 

 burn in the open air as in an inclosed damp vault, whereas the lamps of the 

 ancients nourished their flame best where there was most want of air, only in 

 close vaults and tombs, and were presently extinguished on the least immission 

 of external air, these being qualities necessary, and almost always asserted as 

 concomitants of the ancient sepulchral lamps. To which I answer, that some 

 of the lamps of the ancients burned as well in the open air as in close damp 

 vaults, as several are mentioned by the ancients. 



Another sort of perpetual lamp might be contrived in some coal mines, where 

 the miners, when they have dug so deep that they begin to perceive a want of 

 air, find a bluish flame begin to kindle in the fissures of the coal, which blazes, 

 and moves up and down continually, and is a sort of fire that so little requires 

 air for its continuance, that it burns best when there is least air, and is extin- 

 guished when disturbed by the motion of it, and which therefore must be the 

 fire fittest for this sort of sepulchral lamps. But if it be thought that these 

 lamps did not shine or burn the whole time they were inclosed in the tombs, but 

 were only kindled by the admission of air when opened, I have thought of a way 

 not at all liable to any of the defects or inconveniencies of the two former ways, 

 whereby a glass of liquor inclosed in another, like the urns of Olybius, on im- 

 mission of external air, shall certainly shine, though it did not so before. And 

 it is this, take a small phial, into which put a little of the liquid phosphorus, 

 which, if the phial be stopped, shines not at all, the external air being excluded 

 from it; include this in another glass, as suppose the recipient of an air-pump, 

 in which if the air be well exhausted, solid phosphorus itself will leave ofl^ shining 

 in 10 hours time, though in the summer quarter; and the liquid in fewer, so 

 that it shall shine no more than when the bottle containing it is stopped with a 

 cork ; and both of them will be extinguished proportionably in a yet less time. 



