From this experiment one may conclude, that it is better to prescribe both soap and lime-water for the stone, than any one of them alone; and that if one of these remedies has failed of giving relief, the other ought to be tried: for as the above white _calculus_, which yielded a little to the solution of soap, resisted lime-water; so there may perhaps be others, that are readily dissolved by lime-water, but little affected by soap. Dr. Springsfeld’s experiments with lime-water are somehow not just; for in several _calculi_ I have found the dissolving power of oystershell lime-water above eight times greater than he makes it.” _Some Observations on the lithontriptic Virtue of the_ Carlsbad _Waters, Lime-water, and Soap: In a Letter to Dr._ John Pringle, _F.R.S. from Dr._ Robert Whytt, _F.R.S. and Professor of Medicine in the University of_ Edinburgh. [Read Dec. 15, 1757.] SIR, FROM the experiments related in Dr. Springsfeld’s _Commentatio de prærogativa thermarum Carolinarum, &c._ which you were so good as to send me some time ago, it appears, that these waters are not only possessed of a very extraordinary power of dissolving the stone, but that in this respect they greatly exceed lime-water. (A) Thus, Dr. Springsfeld having infused, for 14 Days, in a heat of 96 degrees of Fahrenheit’s scale, three pieces of the same _calculus_, each weighing 30 grains, in eggshell lime-water, the Carlsbad water, and in the urine of one who daily drank this last water, renewing these several menstruums every day, he found, on the 15th day, that the _calculus_ in the lime-water had lost 1 grain, the _calculus_ in the Carlsbad water 6 grains, and that in urine 5 grains. (B) Again, having divided another _calculus_ into four parts, each of which was reduced to 80 grains, he put the first in oystershell lime-water, the second in Carlsbad water, and the third in the urine of a person who drank this water. After 20 days, during which time the menstruums were renewed every day, and kept in a heat of 96 degrees, the dried _calculi_ had lost of their weight as follows: the first 3 grains, the second 18 grains, and the third 14 grains. Altho’ I make no doubt that Dr. Springsfeld, who appears to be a man of candour, as well as learning, has faithfully related the event of the experiments, which he made; yet either the lime-water he used must have been very weak, or some other mistake must have happened in his experiments: for in all the numerous trials I made, about 15 years ago, of lime-water, as a solvent for the stone, I always found its dissolving power much greater, than it appears in Dr. Springsfeld’s experiments. And as in these trials different urinary stones were used, it can scarcely be imagined, that it was owing to the peculiar hardness of Dr. Springfeld’s _calculi_, that the lime-water made so little impression on them. However, to be still further satisfied of this matter, I made the following experiments.