On the nature of Stones in the Bladder, and Gravel in the Kid- 

 neys, and the Author s exaininatioJi of the question whether the 

 fame can by any means he broken or dissolved. 



J\. VALUABLE friend of mine, the late eminent Constantine 

 Huygens, fometime before his death, did frequently, both in con- 

 verfation, and in his letters to me, exprefs a great defire to know 

 the reafon why the Stone in the bladder produces fuch great pain, 

 and I having the fame dcfire of enquiring into the nature of thofe 

 Stones, procured fome of them for my examination. 



I put one of thefe Stones, which weighed about the fifty-eighth 

 part of a pound weight, into a new glals, to which I applied fo 

 great a heat, that the fait and oil were in part expelled from the 

 .Stone, when the glafs broke ; I thereupon put it into another glafs, 

 and by the application of fire, I drew olFthe remainder of the fait 

 and oil. Upon this I poured rain water, and I obferved that they 

 immediately united with the water. This mixture I suffered in part 

 to evaporate, and then I discovered in it an incredible number of 

 wonderfully minute faline figures, fo fmall indeed, that a mil- 

 lion of them would not equal a grain of fand ; and with all my 

 attention, I could not discover their exact fhape, for the water or 

 the particles in it impeded my view : however, I was perfuaded 

 they had four fides. I alfo examined fome faline particles which 

 adhered to the head of the glafs, and I faw many of them to be 

 thick and broad in the middle, and the ends terminate in a point. 

 I alfo examined the vefTel in which I had put a little of the fait and 

 oil, and here, befides the before -mentioned figures, I faw fome fii- 

 line particles like /^. 21 and 22, and feveral like_^o-. 23, each of 

 them with a rifmg on the back, and all tranfparent like cryflal. 



