From Nº. 4. compared with (A), the dissolving power of soap is to that of the Carlsbad water only as 4 to 6; but it is probable, that had the solution of soap been kept in a heat of 96 degrees, its dissolving power would, even in this experiment, have nearly equalled that of the Carlsbad water. It may, perhaps, be worth while to observe, that a piece of the white chalky calculus of Nº 4. was not in the smallest degree dissolved by lying in lime-water 20 days.
5. In Exper. 19. of my Essay on the Virtue of Lime-water, a piece of a calculus, b, weighing 31 grains, lost 7 grains by being infused 36 hours, in a heat of above 100 degrees, in very strong oistershell lime-water. And in the same water, of a moderate strength, another piece of b lost, in the same time, 5 grains.
In this last experiment, the lithontriptic virtue of lime-water appears to be stronger than in Nº. 1. and 2. above; and greatly exceeds that of the Carlsbad water in Dr. Springsfeld's Exper. (A) and (B).
But altho', from what has been said, it appears not only that lime-water, but also a solution of soap, dissolves the stone in close vessels as fast, nay faster, than the thermæ Carolinæ; yet these last waters, when the calculi were so placed in open vessels, that the water from the fountain might constantly flow along them, effected a much quicker dissolution than lime-water, or even soap-lye, or indeed any known menstruum, except, perhaps, strong spirit of nitre: for, in the first experiment made by Dr. Springsfeld, a calculus of two ounces and a half was, in this manner, quite dissolved in six days. From this experiment, compared with that of Dr. Springsfeld mentioned above (B), it will be found, upon calculation, that the dissolving power of the Carlsbad water, when it is allowed to flow constantly from the fountain along the stone, is nearly 39 times greater than when it is only poured fresh on the calculus once a day[202]. What may have been the reason of this surprising difference of the lithontriptic power of the Carlsbad water in these different circumstances, I will not pretend to say. I think it can scarcely be accounted for from the gentle motion of the water along the surface of the calculus. Was it then owing to some very volatile active part, which the water quickly loses, after being taken from the fountain?
But how great soever the dissolving power of the Carlsbad waters may be, when they issue from the bowels of the earth, yet that they do not communicate a much greater dissolving power to the urine, than lime-water, will appear from comparing the two following experiments.
In Dr. Springsfeld's Exper. (A) above, the urine of a person, who drank the Carlsbad waters, reduced, in 14 days, a piece of calculus, weighing 30 grains, to 25 grains. And in an experiment made by Dr. Newcome, now Lord Bishop of Llandaff, who drank four English pints of oystershell lime-water daily, his Lordship's urine reduced, in four months, a piece of calculus, weighing 31 grains, to three small bits, weighing in all 6 grains[203]. Whence it follows, that the dissolving power of his Lordship's urine must have been to the dissolving power of the urine of the person who drank the Carlsbad waters nearly as 35 to 65[204]. But if we consider, that the calculus infused in the urine of the person who drank the Carlsbad waters was kept always in a heat of 96 degrees, while in Dr. Newcome's experiment, which was made during part of the autumn and winter, no artificial heat was used, it will appear probable, that the dissolving power of his Lordship's urine was little inferior to that of the person who drank the Carlsbad waters; for lime-water, in a heat of 96 degrees, dissolves the calculus at least twice as fast, as in the common heat of the air in winter. Further, if it be attended to, that the quantity of Carlsbad waters drank every day before dinner is from six to eight lib. while his Lordship only drank four lib. of lime-water in 24 hours, it will follow, that whatever the different dissolving powers of the lime-water and Carlsbad waters may be out of the body, yet the former seems, in proportion to the quantity drank, to communicate at least an equal dissolving power to the urine.
But without presuming to decide certainly, as to the comparative virtue of the Carlsbad waters and lime-water, I shall conclude with observing, that tho' the Carlsbad waters are less disagreeable to the taste, and may be drank in larger quantity, than lime-water, yet this last may be drank equally good in all places, and at all seasons of the year; which is not the case with the Carlsbad waters.
November 30. 1757.
An Instance of the Electrical Virtue in the Cure of a Palsy. By Mr. Patrick Brydone.
Read Dec. 15, 1757.