224 Royal Society. 



bodies, those which have the least attraction for that fluid ; and be- 

 ing the best conductors for it, are entirely passive during its transit 

 through them. In confirmation of these views, the author describes 

 experiments in which the electric spark was found to have penetrated 

 through the side of a glass globe, blown to an extreme degree of 

 thinness. An electric jar, from which the air had been partially ex- 

 hausted, could not be made to receive so high a charge as when the 

 contained air was of the usual density, and when entirely exhausted, 

 could not be charged in any sensible degree: when filled with con- 

 densed air, on the other hand, it contained a higher charge than 

 before. The heated, and consequently rarefied air surrounding a red 

 hot iron rod is found to conduct electricity with great facility. The 

 same property is observed in the flame from a blow-pipe, which may 

 be regarded as a hoUov; cone, containing highly rarefied air : as also 

 on a larger scale in that of a volcano. Sir H. Davy had concluded 

 from his experiments on voltaic electricity, that the conducting 

 powers of metals are diminished by heat : but Mr. Ritchie infers, 

 from several experiments which bear more directly upon the ques- 

 tion, that the metals afford no exception to the general law, that in 

 all bodies heat increases the conducting powers ; and explains the 

 apparent anomaly in Sir H. Davy's experiments, by the dissipation 

 of the electricity by tlie rarefied air surrounding the healed metals 

 which were used as conductors. He concludes his paper by descri- 

 bing an experiment, which appears to establish, in respect to this 

 law, a striking analogy between the electric and magnetic influences. 



" Observations on the chemical nature of urinary concretions, 

 particularly of those contained in the collection belonging to the 

 Norfolk and Norwich Hospital," by John Yelloly, M.D., F.R.S. 



The account given by the author of his examination of the urinary 

 calculi contained in the Norwich collection, the total number of 

 which is 649, relates more particularly to those which have been 

 either purposely divided, or accidentally broken in the extraction, 

 and which amount altogether to about 330. He gives a tabular view 

 of the results of his analyses of these calculi, and states, in the order 

 of their occurrence from the centre, the consecutive deposits of the 

 different materials of which they are composed. About one half of 

 the specimens consist only of one description of substance, and the 

 remainder are formed of alternating layers, more or less numerous, 

 of mostof the substances which enter into the composition of human 

 urinary calculi. The distinction between the lithic acid and lithate 

 of ammonia, though generally recognised abroad, was scarcely at- 

 tended to in this country, until noticed by Dr. Prout. The lithic 

 calculi form, as is usual, the most numerous class of concretions in 

 the Norwich collection, where they ainount to nearly a third of the 

 whole number; and if the number of those containing either lithic 

 acid or lithate of ammonia as a nucleus, be taken into account, it will 

 appear, as already observed by Dr. Prout, that not less than two 

 thirds of all urinary calculi either consistof the lithates, or have those 

 substances as their nuclei : whence it may be inferred, that a large 

 proportion of them probably owe their existence to the previous for- 

 mation 



