1 90 Some Remarks upon an iirinary Calculus. 



The anah-sis of ll| grains of this calculus, conducted otherwise 



in the usual way, gave me 



Of phosphate of magnesia and ammonia . . 5*0 

 Phosphate of lime . . . , , . 4'5 



Caihonate of lime . . . . . . '5 



Uric acid, and loss . . . . . . '55 



11 -Jo 



In another calculus principally composed of the ammoniaco- 

 magnesian phosphate, the proportion of cavhonate of lime was 

 only half the ahove quantity; and in a third it was still less. I wish 

 particularly to mention these instances of the occurrence of car- 

 bonate of lime, l)ecause Dr. Henry in his invaluahle work (Ele- 

 ments of Chemistry) calls in question the authority of Proust, 

 in giving carbonate of lime as an ingredient in urinary calculi. 



I have seen somewhere a notice of Mr. Bakewell having dis- 

 covered prelinite in the trap rock of Micklewood near Newport, 

 Gloucestershire. I regret that the particular spot is not men- 

 tioned as I (among many others who have examined the hill) 

 am extremely curious to know the exact locality. This rock is 

 highly interesting, as it exhibits great variety in its structure; 

 being sometimes a sort of iron clay, sometimes trap tuff, in an- 

 other place exhibiting globular concretions of basaltic clinkstone; 

 but the greater part of it is au amygdaloid consisting generally 

 of a basis of iron clay, in v\ hich are oval concretions of green 

 earth, and of a mineral of a white and brown colour resembling 

 calc spar, and which has been by many mistaken as such. I 

 have found the same substance in veins in the rock, and upon 

 analysis I find that it is the mineral called brown spar, aivd 

 contains 44 per cent, of carbonate of magnesia. I am, sir. 



Very rcspectfidly yours, 

 York Crescent, Clifton. VV. H. GiLBY, M.D. 



*** Very well-executed drawings of the '^cinder calculus" 

 accompanied Dr. Gilby's communication ; but being coloured, 

 we cannot with convenience give an engraving of its figure, &c. 

 'In its longest diameter it is about two inches ; in its shortest 

 about one inch and a quarter. The drawings will be taken care 

 of for Dr. G. 



Mr. Smith's Letter to Dr. Gliby. 



My Dear Sir, — The *' cinder calculus " was given to me by 

 Mr. B. G. Burroughs of Clifton, about a year since. Being in 

 the habit of cutting them through, in order to exhibit the nu- 

 cleus, I was not a little surprised to observe the saw in this case 



covered 



