The relative prevalency of the oxalate of lime calculus is very various. The average proportion, as determined by Dr. PROUT is about one in seven. Of the calculi, examined by Mr. BRANDE, 1 in 25 was of the mulberry species; while in the Norwich and Guy's Hospital collections, the proportion is about 1 in 4. In the Bristol collection, one-sixth of the whole, was composed of oxalate of lime, nearly pure; while, including all the concretions containing more or less of the oxalate, the proportion was nearly _one-half_! This great disparity in the proportional frequency of this calculus in different districts of England, clearly shows the great influence of local causes, in determining the character of urinary concretions. From a careful observation of the order of deposition of different species of calculous matter, Dr. PROUT has been enabled to deduce the following general law; "_that, in urinary calculi, a decided deposition of the mixed phosphates is not followed by other depositions_." So that it would appear, that a redundancy in the earthy phosphates is the last link in the chain of diseased alterations, to which the urinary secretion is liable. In the third chapter, under the second subdivision of functional urinary diseases, Dr. PROUT describes the lithic acid diathesis, and communicates several important original observations. After remarking that the dyspeptic are particularly predisposed to lithic acid deposites, he enumerates, as exciting causes of this species of gravel, 1st. _Errors in diet_; 2nd. _Unusual or unnatural exercise of the body or mind, particularly after eating, and the want of proper exercise at all other times_; and 3d. _Debilitating causes_. Under errors of diet, an unusually heavy meal, especially of animal food, and the use of heavy, unfermented bread, or compact, hard-boiled, fat dumplings or puddings, salted and dried meats, acescent fruits, malt liquors, and acescent wines, are enumerated as particularly hurtful in the lithic acid diathesis. The above remarks refer to the amorphous lithic deposites, consisting of lithate of ammonia. In regard to crystallized sediments, or, more properly speaking, gravel, our author makes the following remarks: