Front Matter

ADVERTISEMENT. The Committee appointed by the Royal Society to direct the publication of the Philosophical Transactions, take this opportunity to acquaint the Public, that it fully appears, as well from the council-books and journals of the Society, as from repeated declarations which have been made in several former Transactions, that the printing of them was always, from time to time, the single act of the respective Secretaries, till the Forty-seventh Volume: the Society, as a Body, never interesting themselves any further in their publication, than by occasionally recommending the revival of them to some of their Secretaries, when, from the particular circumstances of their affairs, the Transactions had happened for any length of time to be intermitted. And this seems principally to have been done with a view to satisfy the Public, that their usual meetings were then continued, for the improvement of knowledge, and benefit of mankind, the great ends of their first institution by the Royal Charters, and which they have ever since steadily pursued. But the Society being of late years greatly enlarged, and their communications more numerous, it was thought advisable that a Committee of their members should be appointed, to reconsider the papers read before them, and select out of them such as they should judge most proper for publication in the future Transactions; which was accordingly done upon the 26th of March, 1752. And the grounds of their choice are, and will continue to be, the importance and singularity of the subjects, or the advantageous manner of treating them; without pretending to answer for the certainty of the facts, or propriety of the reasonings, contained in the several papers so published, which must still rest on the credit or judgment of their respective authors. It is likewise necessary on this occasion to remark, that it is an established rule of the Society, to which they will always adhere, never to give their opinion, as a Body, upon any subject, either of Nature or Art, that comes before them. And therefore the thanks, which are frequently proposed from the Chair, to be given to the authors of such papers as are read at their accustomed meetings, or to the persons through whose hands they received them, are to be considered in no other light than as a matter of civility, in return for the respect shown to the Society by those communications. The like also is to be said with regard to the several projects, inventions, and curiosities of various kinds, which are often exhibited to the Society; the authors whereof, or those who exhibit them, frequently take the liberty to report, and even to certify in the public newspapers, that they have met with the highest applause and approbation. And therefore it is hoped, that no regard will hereafter be paid to such reports and public notices; which in some instances have been too lightly credited, to the dishonour of the Society. CONTENTS. I. On the effects of temperature on the intensity of magnetic forces; and on the diurnal variation of the terrestrial magnetic intensity. By Samuel Hunter Christie, Esq. M. A. of Trinity College, Cambridge, Fellow of the Cambridge Philosophical Society: of the Royal Military Academy. Communicated by the President II. The Croonian Lecture. On the existence of Nerves in the Placenta. By Sir Everard Home, Bart. V. P. R. S. III. Observations on the changes the Ovum of the Frog undergoes during the formation of the Tadpole. By Sir Everard Home, Bart. V. P. R. S. IV. A general Method of Calculating the Angles made by any Planes of Crystals, and the Laws according to which they are formed. By the Rev. W. Whewell, F. R. S. Fellow of Trinity College, Cambridge. V. Explanation of an optical deception in the appearance of the spokes of a wheel seen through vertical apertures. By P. M. Roget, M. D. F. R. S. VI. On a new photometer, with its application to determine the relative intensities of artificial light, &c. By William Ritchie, A. M. Rector of the Academy at Tain. Communicated by the President. VII. The description of a floating Collimator. By Captain Henry Kater, F. R. S. VIII. Notice on the Iguanodon, a newly discovered fossil reptile, from the sandstone of Tilgate forest, in Sussex. By Gideon Mantell, F. L. S. and M. G. S. Fellow of the College of Surgeons, &c. In a Letter to Davies Gilbert, Esq. M. P. V. P. R. S. &c. &c. &c. Communicated by D. Gilbert, Esq. IX. An experimental enquiry into the nature of the radiant heating effects from terrestrial sources. By Baden Powell, M. A. F. R. S. of Oriel College, Oxford. Communicated by J. F. W. Herschel, Esq. Sec. R. S. X. On the Anatomy of the Mole-cricket. By J. Kidd, M.D. and F. R. S. Reg. Prof. of Medicine in the University of Oxford. p. 203 XI. Further observations on Planariae. By J. R. Johnson, M.D. F.R.S. 247 XII. On the influence of nerves and ganglions in producing animal heat. By Sir Everard Home, Bart. V. P. R. S. presented by the Society for the Improvement of Animal Chemistry. 257 XIII. An Essay on Egyptian Mummies; with observations on the art of embalming among the ancient Egyptians. By A. B. Granville, M.D.; F. R. S.; F. L. S.; F. G. S.; M.R.I. one of His Royal Highness the Duke of Clarence's Physicians in Ordinary, &c. 269 XIV. On the temporary magnetic effect induced in iron bodies by rotation. In a Letter to J. F. W. Herschel, Esq. Sec. R. S. by Peter Barlow, Esq. F.R.S. Communicated April 14th, 1825. 317 XV. Further researches on the preservation of metals by electrochemical means. By Sir Humphry Davy, Bart. Pres. R. S. 328 XVI. On the Magnetism of Iron arising from its rotation. By Samuel Hunter Christie, Esq. M.A. of Trinity College, Cambridge; Fellow of the Cambridge Philosophical Society; of the Royal Military Academy. Communicated April 20, 1825, by J. F. W. Herschel, Esq. Sec. R. S. 347 XVII. Some account of the transit instrument made by Mr. Dollond, and lately put up at the Cambridge Observatory. Communicated April 13, 1825. By Robert Woodhouse, Esq. A. M. F. R. S. p. 418 XVIII. On the fossil Elk of Ireland. By Thomas Weaver, Esq. Member of the Royal Irish Academy, of the Royal Dublin Society, and of the Wernerian and Geological Societies. 429 XIX. Microscopical observations on the Materials of the Brain, and of the Ova of Animals, to show the analogy that exists between them. By Sir Everard Home, Bart. V. P. R. S. Read at the Society for promoting Animal Chemistry, April 12, 1825. 436 XX. On new compounds of carbon and hydrogen, and on certain other products obtained during the decomposition of oil by heat. By M. Faraday, Esq. F. R. S. Cor. Mem. Royal Academy of Sciences of Paris, &c. 440 XXI. Account of the repetition of M. Arago's experiments on the magnetism manifested by various substances during the act of rotation. By C. Babbage, Esq. F. R. S. and J. F. W. Herschel, Esq. Sec. R. S. 467 XXII. On the magnetism developed in copper and other substances during rotation. In a Letter from Samuel Hunter Christie, Esq. M. A. &c. to J. F. W. Herschel, Esq. Sec. R. S. Communicated by J. F. W. Herschel, Esq. 497 XXIII. On the annual variations of some of the principal fixed Stars. By J. Pond, Esq. F. R. S. Astron. Royal. 510 XXIV. On the nature of the function expressive of the law of human mortality, and on a new mode of determining the value of Life Contingencies. In a Letter to Francis Baily, Esq. F.R.S. &c. By Benjamin Gompertz, Esq. F.R.S. p. 513 APPENDIX. Presents received by the Royal Society from November 1824, to June 1825. Index. Meteorological Journal kept at the Apartments of the Royal Society, by order of the President and Council.