JOHN WILLIAM AND SOLD BY PARKER, WEST STRAND, LONDON; J. & J. J. DEIGHTON; AND T. STEVENSON, CAMBRIDGE. M.DCCC.XXXVIII. CONTENTS OF THE SIXTH VOLUME. N°. I. RESEARCHES in Physical Geology: by WILLIAM HOPKINS, M.A. II. Investigation of the Equation to Fresnel's Wave Surface: by ARCHIBALD III. On the Resolution of Equations in Finite Differences: by the Rev. R. PAGE IV. Geometrical Theorems, and Formula, particularly applicable to some Geodetical Problems: by WILLIAM WALLACE, A.M. F.R.S. Edin., F.R.A.S. Lond.... 107 V. Mathematical Considerations on the Problem of the Rainbow, shewing it to belong to Physical Optics: by R. POTTER, Esq. VI. On the Dispersion of Light, as explained by the Hypothesis of Finite Intervals : VII. Sketch of a Method of Introducing Discontinuous Constants into the Arithme- tical Expressions for Infinite Series, in cases where they admit of Several Values. In a Letter to the Rev. George Peacock, &c. &c: by AUGUSTUS VIII. Piscium Maderensium Species quædam novæ, vel minus rite cognitæ breviter descripta. Auctore R. T. LowE, A.M. Iconibus illustravit M. YOUNG..... 195 On the Motion of a System of Particles, considered with reference to the Phenomena of Sound and Heat: by PHILIP KELLAND, Esq... XI. On the Relative Quantities of Land and Water on the Surface of the Terra- XIII. On the Explanation of a Difficulty in Analysis noticed by Sir William Hamilton: by ARTHUR AUGUSTUS MOORE, Esq.... XIV. On the Transmission of Light in Crystallized Media: by PHILIP KELLAND, Esq. 323 XV. Supplement to the Memoir on the Transmission of Light in Crystallized Media: On the Reflexion and Refraction of Sound: by G. GREEN, Esq.... On a new Genus of Fossil Multilocular Shells, found in the Slate-Rocks Mathematical Investigation of the Effect of Machinery on the Wealth of a Community in which it is employed, and on the Fund for the Pay- ment of Wages: by JOHN TOZER, Esq. B.A..... Novitia Flora Maderensis: or Notes and Gleanings of Maderan Botany: ADVERTISEMENT. THE Society as a body is not to be considered responsible for any THE Society takes this opportunity of expressing its grateful I. Researches in Physical Geology. By WILLIAM HOPKINS, M.A., Fellow of the Cambridge Philosophical Society, and of the Geological Society, and Mathematical Lecturer of St Peter's College, Cambridge. [Read May 4, 1835.] INTRODUCTION. NOTWITHSTANDING the appearances of irregularity and confusion in the formation of the crust of our globe which are presented to the eye in the contemplation of its external features, geologists have been able in numerous instances to detect, in the arrangement and position of its stratified masses, distinct approximations to geometrical laws. In the phenomena of anticlinal lines, faults, fissures, mineral veins, &c., such laws are easily recognized; and though, when we consider how large a portion of the surface of the earth remains geologically unexplored, it may appear premature to assert that these are perfectly general laws, yet, founding our reasoning on our knowledge, and not on our ignorance, and feeling that confidence which we are entitled to feel in the universality of the laws and operations of nature, we shall, I conceive, be justified, if not in the absolute conclusion, at least in the presumption, that the laws already observed in phenomena such as those above mentioned will be found, by the wider extension and increased accuracy of geological research, to be the approximative general laws of those phenomena. If the legitimacy of this inference be allowed, we are necessarily led to the conclusion, that the phenomena alluded to are referrible not to the particular and irregular action of merely local causes, but to the more widely diffused action of some simple cause, general in its nature with respect to every part of the globe, and general in its action at least with respect to the whole of each district throughout VOL. VI. PART I. A |