254 PHILOSOPHICAL TRANSACTIONS. [ANNO 1798. 



It is a remarkable circumstance, that the effect of the fluid at z increased regu- 

 larly as the angle decreased; for, though I did not measure the negative effects, I 

 could plainly perceive that that was the case; whereas, the effects at m and x in- 

 creased to about the middle of the quadrant, and then decreased. At 10°, the 

 obliquity was such, that the section of the stream extended very nearly from one 

 side of the lever to the other. As it appears by experiment, that the velocity of 

 the fluid flowing out of the vessel, was equal to the velocity which a body acquires 

 in falling down the altitude of the fluid above the orifice, the square of the velocity 

 must be in proportion to that altitude. To find therefore, in this case, whether 

 the resistance varied as the square of the velocity, I let the water flow perpendicu- 

 larly against the plane, fig. 1 , at different depths, and I always found the resistances 

 to be in proportion to the depths, and therefore in proportion to the square of the 

 velocity, agreeing with what takes place when the body moves in the fluid. 



II. Experiments and Observations, tending to show the Composition and Properties 

 of Urinary Concretions. By Geo. Pearson, M. D., F. R. S. p. 15. 



1. Historical Observations. — Urinary concretions have obtained their denomi- 

 nations, like most other things, from their obvious properties. Accordingly, in 

 our language, they are popularly known by the names Stone and Gravel, or Sand, 

 from their resemblance to the states of earth so named: and we find names of the 

 same import in other languages, such as AiOo?, (Aretaeus;) x^ixtng, (Caelius Aure- 

 Kanus;) faw^y (Aretaeus;) x»Wu», (various authors;) Calculus, (Celsus and Pliny ;) 

 Sabulum, (various authors.) In other languages, and especially in those now 

 spoken, it is unnecessary to notice names which have the same meaning. 



The notion very generally entertained, of the nature of urinary concretions, con- 

 sisted with the terms, till the last 20 years; though the experiments of Slare, Fred. 

 Hoffman, and Hales, long before showed that these substances commonly consist 

 of animal matter. Galen indeed imagined that <p\typoi, or viscid animal matter, is 

 the basis of animal concretions; but in his days earth was believed to be the basis 

 of animal matter. Alkaline medicines were however employed by the Greek phy- 

 sicians, in diseases from calculi. 



The experiments of the alchemists also made it appear, that earth was only a 

 part of the matter of concretions. It was probably the observation of the deposi- 

 tion and crystallization of saline bodies, which suggested the notion of urinary 

 calculi being of the nature of tartar. Such was the opinion of Basil Valentine, 

 and after him of Hochener, better known by the name of Paracelsus; but whether 

 the latter adopted the denomination Duelech from its import, or from caprice, has 

 not been explained. Van Helmont, a century after his prototype Paracelsus, being 

 struck with the experiment in which he discovered the concretion of salts in dis- 

 tilled urine by alcohol, was led to depart from his adored master's opinion, with 

 respect to the nature of calculi; though he acknowledges the merit of Paracelsus, 

 in having discovered the solvent Ludus, a calcareous stone also called Septarium, , 



