400 Dr. Wollaston's Analysis , &c. 
affords us great variety of proofs of its presence. Particles of 
red sand (as they are called) are its crystals. Fragments also 
of larger masses, and small stones, are frequently passed ; and 
it is probable that the majority of appearances in the urine 
called purulent, are either the acid itself precipitated too quickly 
to crystallize, or a neutral compound of that acid with one of 
the fixed alkalies. 
Beside this species, the fusible calculus has afforded decisive 
marks of its presence in the case which furnished me with my 
specimen of triple crystals ; and by the description given by 
Mr. Forbes (in his Treatise upon Gravel and Gout, ed. 1793, 
p. 65.) of a white crystallized precipitate, I entertain no doubt 
that his patient laboured under that variety of the disease. 
