244 PHILOSOPHICAL TRANSACTIONS. [aNNO 1675. 



millions of muids of water. But taking this quantity out of the 281 millions 

 that are in the conservatory above described, there will remain yet above 

 188* millions of muids, which amounts to almost five times as much, and 

 which serves to furnish for the losses, diminutions, and other wastes, above 

 noticed. So that there needs but the sixth part of the rain and snow-water that 

 falls in a year, to run continually through the whole year. 



On Damps in Mines. By Mr, Jessop. N^lig, p. 450. 



Damps are most generally observed to come about the latter end of May, and 

 to continue during the heat of summer ; and in those places which have damps 

 all the year long, yet they observe them to be most violent at that season. — I 

 never heard of damps that kindled of themselves, although I have been told, 

 that in some places they have been kindled by the motion of the sled, in which 

 they draw their coals. — Damps generally are held to be heavier than the air ; 

 but this was manifestly lighter, for it lay towards the top of the bink. — On the 

 breaking of the fulminating damp there proceeds a dark smoke of the smell and 

 colour of that which proceeds from fired gunpowder. 



Some damps will quite extinguish all those fires that are let down into them, 

 be they never so many successively, or never so great ; and fire is observed to 

 be so far from curing, that it often creates damps in places not otherwise sub- 

 ject to them. Indeed they are a present remedy, if by their means a circulation 

 of air through the infected place can be made, otherwise they do hurt ; and 

 those grooves in which they are forced to break their rocks by the help of great 

 fires, are seldom free from damps. — Damps are common both in dry and wet 

 grounds. — Damps are observed to be most pestilential, and to kill the soonest, 

 that are in grooves not stirred for many years ; especially if such grooves have 

 formerly had great fires in them. 



The general opinion of the workmen is, that there are some damps which 

 kill by reason of the noisome steam. For they say there is no groove that wants 

 air, be it never so deep ; but the air stagnating in very deep grooves or pits, 

 the grosser parts must needs at length separate themselves by their own weight, 

 and subsiding to the bottom, there corrupt, and consequently get malignant 

 qualities, especially in the summer time, when the sun promotes the fermenta- 

 tion. — Damps will often follow the water, and particularly this sort of fiery 

 damp.'l' 



* There is some mistake in these numbers, as 2444- would remain. 



f Concerning the nature of these damps, see volume I, p. l6, of this Abridgement. 



