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estimation, can never have taken place beneath the present rectilinear and parallel strata.

Dr. Richardson assumes as a fact, that strata having very strong resemblance were once continuous, however interrupted we now find them; for instance, the stratified remnants at the tops of the Seafin and Slievegallon, between which the valley of the Mayola is an ex- cavation 1700 feet deep and three miles wide, were originally con- nected in their present position by similar materials, the whole of which have been completely carried away. And again, to the north- ward, between Seafin and Camtogher, the same stupendous operations have carried away the parts which formerly connected these undis- turbed remains of the same strata.

The number of basaltic hummocks thus left on the tops of various mountains, is represented to be considerable, as if they had been left by the unknown sculptor for the express purpose of showing how high the original surface of the country formerly reached,——-a conclusion which appears formidable; but the author does not admit that any- thing is absurd, incredible, or impossible, in geology and cosmogouy.

A Letter on the Diferences in the Structure of Calculi, which arise from their being formed in diferent Parts of the Urinary Passages; and on the Efects that are produced upon them, by the internal Use of solvent Medicines, from Mr. William Brande to Everard Home, Esg. RES. Read May 19, 1808. [Phil. Trans. 1808, p. 223.]

Mr. Brande’s observations were made during an examination of the calculi contained in the Hunterian Museum, and of some also in the possession of Mr. Home.

Three calculi, formed in the kidneys, were examined. One con- sisted of uric acid, nearly pure ; another, weighing seven grains, con- tained 4—;— uric acid, and 2-;— animal matter. A third consisted of oxalate of lime; and it is added that afine powder is also voided from the kidneys, consisting of the ammoniacal phosphate of mag- nesia, and of phosphate of lime.

Calcnli retained in the infundibula, or pelvis of the kidneys, may be increased either by a deposition of uric acid, or may be coated by an external lamina, consisting of the phosphates.

Calculi met with in the bladder, are of four kinds.

1. Formed on nuclei of uric acid, from the kidneys.

2. On nuclei of oxalate of lime, from the kidneys.

3. Formed on sand or mucus deposited in the bladder.

4. Formed on extraneous bodies introduced into the bladder.

Those consisting of uric acid vary in colour, from a deep reddish brown to apale yellowish brown. Those containing phosphate of lime, and the triple phosphate of magnesia, are whiter, and are often soft and friable. Those which contain oxalate of lime, callcd mulberry calculi, are browner, harder, and less soluble.

Out of 150 examined by bin Brande,

16 were composed of uric acid.