554 
APPENDIX. 
Size, — The acicular vary exceedingly in their measurement, 
some being not more than -joV^ length, whilst 
others will be as much as -jL. The conglomerate form is not 
subject to so much variation, varying only from to aio part 
of an inch. The size c/ the rhombohedral and other forms of 
crystals has no uniformity as to measurement, some being not 
more than 20V o’ whilst others are the part of an inch. 
“ Composition. — According to Raspail, the composition of the 
acicular and conglomerate forms differs, the former being phos- 
phate, whilst the latter are oxalate of lime. Unger mentions that 
Buchner, Nees von Esenbeck, and others, have found that their 
bases are sometimes lime, magnesia, and silica, the latter not often 
occurring ; and that these bases are united to carbonic, oxalic, and 
phosphoric acids. The whole of these assertions are more or less 
correct, but Raspail has only given us negative proofs of their 
composition. It is not difficult to obtain positive ones, by the 
following experiments : — 
“ If Raphides of the conglomerate form (perfectly free from 
cellular tissue) be heated red hot, it will be observed that they at 
first become black and again white, as the heating is continued to 
redness : in this state they readily dissolve in weak nitric or 
hydrochloric acid, with effervescence ; if to this solution oxalate of 
ammonia be added, a copious white precipitate is obtained, which 
indicates that the base in this case has been lime. In detecting 
the acid united with the lime, the proceeding is a little more com- 
plicated. For this purpose the crystals are to be dissolved in dilute 
nitric acid, which occurs without effervescence ; to this solution 
nitrate of silver is to be added, when a heavy white precipitate is 
produced, which, when washed with distilled water to free it from 
any excess of acid and nitrate of silver, is to be dried ; if after this 
a small portion be heated in the flame of a lamp it explodes, by 
which it is proved that the precipitate is oxalate of silver. These 
results, which may be performed with certainty with conglomerate 
Raphides, plainly proves their composition to be oxalate of lime. 
“ The acicular can be demonstrated to be phosphate of lime, by 
proceeding thus. If heated red hot, they do not dissolve in acids 
with effervescence, a fact which essentially distinguishes the com- 
position of the two kinds. When dissolved in dilute nitric acid, if 
oxalate of ammonia be added, we have the characteristic precipitate 
of lime ; if with a portion of the acid solution be mixed a little 
nitrate of silver, a white precipitate is not obtained, as in the last 
case, but one of a lemon colour, which is such as denotes the 
