Siliceous Deposits from the Urine. 257 



Vauquelin, and in one by Professor Wurzer. I believe I was 

 the first, so far as I have been able to ascertain, publicly to 

 notice the deposition of crystallized silex as gravel from the 

 urine, the particulars of which have been already detailed in 

 an earlier number of this Journal. At the period of sending 

 the communication, and for some considerable time afterwards, 

 I continued to enjoy frequent opportunities of witnessing the 

 appearance of this deposit. It was not, however, a constant 

 occurrence, but was occasionally interrupted for a time, and 

 at various intervals reappeared. Upon one occasion, I trans- 

 mitted the gravel, precisely as passed, to a gentleman * much 

 .devoted to researches of this description, with a request that 

 .he would acquaint me with his views upon the subject; and 

 upon receiving his reply, I was much chagrined to learn that 

 he had not been able to discover any siliceous matter in the 

 specimen with which I had furnished him. As I placed the 

 utmost reliance upon the correctness of this gentleman's con- 

 ceptions, and the accuracy of his judgment, I almost regretted 

 that I had committed my paper to the press, the more espe- 

 cially as, upon several after occasions, the gravel exhibited all 

 the sensible characters of the siliceous depositions previously 

 observed; but upon chemical examination, it did not afford 

 even a trace of silex. However, it was not long before I was 

 gratified by the reappearance of the silex, a portion of which 

 the specimens being passed at different times I sent to my 

 friend, and found that he confirmed me in the fact of their 

 siliceous nature. The only question with him then was their 

 urinary origin ; but upon this subject I fully satisfied myself by 

 having the urine passed in my presence, so as to prevent the 

 .possibility of practising any deception. 



Since the publication of that paper, Dr. Yelloly, of Norwich, 

 discovered silex in small granules, * imbedded in the substance 

 of an oxalate of lime calculus,' from the Norwich collection. 

 The calculus weighed about five grains, and was taken from a 

 boy about nine years old. The examination of this calculus, 

 with the chemical proofs of the intermixture of siliceous gra- 

 nules, is detailed at length in Dr. Yelloly's paper, published in 

 4he Philosophical Transactions. Dr. Yelloly, in consequence 



* Dr. Prout. 



