VOL. LXXXVIJ.] PHILOSOPHICAL TRANSACTIONS. 217 



of a salt, apparently common salt, but too minute for accurate examination. Dis- 

 tilled vinegar dissolves no part of it, even when powdered. Marine acid dissolves 

 the phosphorated lime and phosphorated magnesia, leaving nothing but a little 

 charcoal. From this solution vitriolic acid occasions a precipitate of selenite, after 

 which triple crystals may be formed by addition of volatile alkali. — (13) Marine 

 acid also acts readily on a fragment of the stone, leaving only yellowish laminae of 

 lithic acid. When the solution has been evaporated to dryness, sal ammoniac 

 may be sublimed from it ; and the 2 phosphorated earths are found combined with 

 more or less of marine acid, according to the degree of heat applied. If the pro- 

 portion of the earths is wished to be ascertained, acid of sugar will separate them 

 most effectually, by dissolving the phosphorated magnesia, and forming an inso- 

 luble compound with the lime. 



(14) Caustic vegetable alkali has but little effect on the entire stone; but if 

 heated on the stone in powder,- a strong effervescence takes place from the escape 

 of alkaline air, and the menstruum is found to contain lithic acid precipitable by 

 any other acid. Some phosphoric acid also, from a partial decomposition of the 

 triple crystals, is detected by nitrated quicksilver. — (15) The triple crystals alone 

 are scarcely fusible under the blow-pipe; phosphorated lime proves still more re- 

 fractory; but mixtures of the 2 are extremely fusible, which explains the fusibility 

 of the calculus. The appearance of the lithic strata, and the small proportion 

 they bear to the other ingredients, shows that they are not an essential part, but an 

 accidental deposit, that would be formed on any extraneous substance in the 

 bladder, and which probably in this instance concretes during any temporary in- 

 terval that may occur in the formation of the crystals. — I come now to what has 

 been called 



Mulberry calculus. — This stone, though by no means overlooked, and though 

 pointed out as differing from other species, has not, to my knowledge, been sub- 

 jected to any further analysis than is given, in the 2d vol. of the Med. Trans., by 

 Dr. Dawson, who found that his lixivium had little or no effect on it; and in the 

 Phil. Trans, by Mr. Lane, who, among other simple and compound stones, gives 

 an account of the comparative effects of lixivium and heat on a few specimens of 

 mulberry calculus, (viz. N° 7, 8, 9, 10); but neither of these writers attempted 

 to ascertain the constituent parts. Though the name has been confined to such 

 stones as, from their irregularity, knotted, surface, and dark colour, bear a distant 

 resemblance to that fruit, I find the species, chemically considered, to be more 

 extensive, comprehending also some of the smoothest stones we meet with ; of 

 which one in my possession is of a much lighter colour, so as to resemble in hue, 

 as well as smoothness, the surface of a hemp-seed. From this circumstance it 

 seems not improbable that the darkness of irregular stones may have arisen from 

 blood voided in consequence of their roughness. The smooth calculus I find to 

 consist of lime united with the acids of sugar and of phosphorus. The rougher 

 specimens have generally some lithic acid in their interstices. 

 vol. xviii. F F 



