AND ON THE INTRODUCTION OF DECOMPONENTS INTO THE BLADDER. 13 
consist of magnetic particles of phosphuret of iron, affording another proof of the 
presence of phosphoric acid in the precipitate. 
With respect to the filtered solution, half of it, amounting to ten ounces, on being 
cautiously evaporated to dryness, yielded rather more than nine grains of solid 
residue, which, however, was not analysed. The remaining ten ounces were treated 
with sulphuretted hydrogen, so as to decompose the whole of the salt of lead : it was 
then filtered, boiled, and tested with oxalate of ammonia, which produced after a 
time a trifling precipitation of lime : the superaddition of liquid ammonia gave no 
evidence of the presence of magnesia. 
At the commencement of the experiment the solid materials amounted to 120 
grains, viz.— 
Seven calculous fragments =100 grs. 
Nitro-saceharate of lead in solution =20 
120 
After the operation the following seems to have been the arrangement of the in- 
gredients : — 
Calculous fragments after immersion for forty minutes . . . = 88 grs. 
Precipitate separated by filtration and dried =11 
Residue of filtered fluid after evaporation = 19 
Unaccounted for = 2 
120 
Supposing the precipitate from the calculi to have consisted entirely of phosphate 
of lead, the equivalent of acid would, on a rough calculation, have been 2 4 ; so that, 
had the assay been inorganic, or definite in composition, the exact amount of decom- 
posed salt might have been estimated. Under existing circumstances rude approxi- 
mations are sufficient ; but I hope to be enabled to illustrate this part of the subject 
at some future period, by more careful and extended analyses. 
The second experiment was conducted by suspending a fragment of fusible calcu- 
lus, weighing thirty grains, in five ounces of the nitro-saccharate solution for half an 
hour. At the expiration of this period the fragment had lost eight grains, and the 
precipitate arising from its decomposition, when carefully dried, weighed rather more. 
The filtered fluid, treated as in the former experiment, contained a small quantity of 
lime. 
In the course of the present experiment some very curious and interesting pheno- 
mena were observed. A copious, dense, white sediment, descended as usual in a 
stream from the calculus ; but, besides this, an ascending current was remarked : it 
consisted of air bubbles, bearing with them a white stream, similar to, though smaller 
than that which was seen descending ; on arriving at the surface the bubbles escaped, 
and the white particles they had rendered buoyant, subsided steadily, like sparks 
from an exploded rocket. This circulation, similar to the ascending and descending 
