VOL. XLVI.] PHILOSOPHICAL TRANSACTIONS. 40 



those waters. Hence we see how much stronger the water near the bottom is, 

 than at the surface ; even when the preceding rains have been but moderate ; 

 for they had not as yet been sufficient to raise the springs in this country much. 

 Hence we see that the stronger lower water may easily be come at by means of a 

 pump ; as also, that the upper land springs, soon after rains, make the water 

 near the surface weaker : but, in long dry weather, when there are no land- 

 springs, the surface-water, and that at the bottom, are nearly of an equal 

 strength : for it requires time for the saline mineral virtue to be equally diffused 

 through a mass of that depth of water, whose upper part is incessantly weakened 

 by a land-spring of fresh water. Hence we see how adviseable it is, in order to 

 keep out the land-springs, to dig a narrow trench some feet depth, round the 

 well, to be filled with stiff clay well rammed. 



The mineral virtue in this water seems to be much like that of Cheltenham, 

 in its shooting into very bitter, regular, oblong crystals, which are, on that ac- 

 count, called nitrous; though they are not a true nitre; for neither these, nor 

 those of Cheltenham, will deflagrate or flash in touch-paper, nor on burning 

 charcoal, as true nitre will do; some of which will retain their form and firmness 

 for 1 7 months after being crystallized ; whereas the crystallized salts of several other 

 purging waters have crumbled, and in a great measure wasted away in much less 

 time : a greater proportion of the salts of Jessop's well shoot into oblong crys- 

 tals, than those of Cheltenham , and its water also gives a stronger green tinc- 

 ture, with violet-flowers. The purging quality resides chiefly in these crys- 

 talline salts, and a small proportion of common salt ; some of which there is in 

 all these mineral waters. 



The proportion also of its earthy calcareous matter, is but -pf.,- part of it ; 

 which, like that of Cheltenham, is but little, in comparison of the much greater 

 quantity of it in other purging waters : it is also soft and impalpable, like that 

 of Cheltenham, and not harsh and coarse, as it is in some other purging waters. 



And as the quantity of purging salt in this water is considerably greater than 

 in any other, so it is found by experience, that proportionably a less quantity of 

 it suffices, which makes it sit the better on the stomach. It is also observed to 

 exhilarate those who take it. 



It was observable of the sediment of several of these waters, that when dried, 

 and while hot, there ascended plenty of invisible volatile salt fumes, so pungent 

 that the nose could not bear them. Hence we may reasonably conclude, that 

 the waters which abound most with purging salts, such as those of Jessop's well, 

 should be proportionably preferable to weaker waters, which are strengthened by 

 boiling half away ; by which not only the more subtile active parts are evapo- 

 rated ; but those that are left are decompounded, and formed into new grossed 

 combinations ; as are also the calcareous particles, which are so fine as to pass 



VOL. X. H 



