 |
|
Cosa dicono le persone - Scrivi una recensioneNessuna recensione trovata nei soliti posti. Libri correlati
Indice
Altre edizioni - Visualizza tutto
Parole e frasi comuniangle angular aperture aperture apparatus argon atmosphere axis bolometer bright camera cent chromosphere collimator comparison compound prism computed corona corresponding Crossley reflector curve density determined deviation disk dispersion distance diurnal motion Earth eclipse epoch equal equation escape experiments focal length formula gases give given glass heliostat helium hydrogen inches instrument intensity investigation lens Lick Observatory light line of apsides line of sight magnitude mass Maxwell's law mean measures metallic method minima mirror motion nebula number of molecules objective observations obtained orbit photographic photometric planet plate plate-holder platinum polar position possible Potsdam prism Professor radial velocity radiation refracting refractor right ascension ring rotation sensitometer siderostat silicon simple prisms single exposure slit solar nebula solar spectrum spectra spectrograph spectroscope star stellar stratum sufficient surface TABLE telescope temperature tion tube vanadium variation velocity wave-length Brani popolariPagina 350 - While I must leave to others an estimate of the importance of these conclusions, it seems to me that they have a very direct bearing on many, if not all, questions concerning the cosmogony. If, for example, the spiral is the form normally assumed by a contracting nebulous mass, the idea at once suggests itself that the solar system has been evolved from a spiral nebula... Pagina 376 - ... instrument is too low to permit even a tolerably accurate measurement. A further reason for the small success doubtless lay in the unsuitability of the apparatus, which was especially lacking in stability. When I made the first attempt in 1887, with the assistance of Professor Scheiner, to record photographically the displacements of the lines in stellar spectra, and then to measure them as accurately as possible on the spectrograms, it very soon appeared that this constituted a very marked advance... Pagina 349 - ... 1. Many thousands of unrecorded nebulae exist in the sky. A conservative estimate places the number within the reach of the Crossley reflector at about 120,000. The number of nebulae in our catalogues is but a small fraction of this. " 2. These nebulae exhibit all gradations of apparent size from the great nebula in Andromeda down to an object which is hardly distinguishable from a faint star disk. " 3. Most of these nebulae have a spiral structure. Pagina 114 - It may be conjectured, then, that the best hypothesis in the early stages of the swarm is the isothermal-adiabatic arrangement, and later an adiabatic sphere. It has not seemed worth while to discuss this latter hypothesis in detail at present. The same investigation also gives the coefficient of viscosity of the quasi-gas, and shows that it is so great that the meteor-swarm must, if rotating, revolve nearly without relative motion of its parts, other than the motion of agitation. Pagina 130 - It is of such a character, and the numerical discrepancies are so great, that it seems to render the nebular hypothesis in the simple form in which it has usually been accepted absolutely untenable unless some fundamental postulates now generally accepted are radically erroneous. It seems a necessary inference from the results of the discussion that the solar nebula was heterogeneous to a degree not heretofore considered as being probable, and that it may have been in a state more like that exhibited... Pagina 348 - ... in the case of very small nebulae, is surprising. It is an interesting fact that these photographs confirm (in some cases for the first time) many of the visual observations made with the six-foot reflector of the EARL OF ROSSE. Incidentally, in making these photographs, great numbers of new nebulae have been discovered. The largest number that I have found on any one plate is thirty-one. Eight or ten is not an uncommon number, and few photographs have been obtained which do not reveal the existence... Pagina 326 - The Crossley reflector, at present the largest instrument of its class in America, was made in 1879 by Dr. AA COMMON, of London, in order to carry out, and test by practical observation, certain ideas of his respecting the design of large reflecting telescopes. For the construction of the instrument embodying these ideas, and for some fine astronomical photographs obtained with it, Dr. COMMON was awarded the gold medal of the Royal Astronomical Society in 1884. In 1885, Dr. COMMON, wishing to make... Pagina 329 - ... Kepler, which is reserved for domestic purposes and is not allowed to pass through the machinery. The dome itself, 38 feet 9 inches in diameter, is made of sheet-iron plates riveted to iron girders. It also carries the wooden gallery, ladders, and observing platform, which are suspended from it by iron rods. The apparatus for turning the dome consists of a cast-iron circular rack bolted to the lower side of the sole-plate, and a set of gears terminating in a sprocket-wheel, from which hangs an... Pagina 64 - ... would be out of place here. Suffice it to say that the English monasteries in Henry III.'s time counted by hundreds. Pagina 390 - ... act, and it is a pleasure to be able to say that the requirements of the said section are being very fairly complied with by merchants and manufacturers. Informazioni bibliografiche
|