The Microscope: Its History, Construction, and Application, Being a Familiar Introduction to the Use of the Instrument, and the Study of Microscopical Science

Portada
G. Routledge & Sons, 1898 - 704 páginas
 

Comentarios de la gente - Escribir un comentario

No encontramos ningún comentario en los lugares habituales.

Otras ediciones - Ver todas

Términos y frases comunes

Pasajes populares

Página 14 - When a ray of light passes from one medium to another, it is refracted so that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the velocities in the two media.
Página 248 - ... screw motion to focus the slit. A side slit capable of adjustment admits when required a second beam of light from any object whose spectrum it is desired to compare with that of the object placed on the stage of the microscope. This second beam of light strikes against a very small prism, suitably placed inside the apparatus, and is reflected up through the compound prism, forming a spectrum in the same field with that obtained from the object on the stage. a is a brass tube carrying the compound...
Página 476 - The existing plants whence we derive our analogies in dealing with the vegetation of this early period, contribute but little, if at all, to the support of animal life. The ferns and their allies remain untouched by the grazing animals. Our native club-mosses, though once used in medicine, are positively deleterious; the horsetails, though harmless, so abound in silex, which wraps them round with a cuticle of stone, that they are rarely cropped by cattle; while the thickets of fern which cover our...
Página 620 - The mode in which the ball is formed is very curious : the mother spider " uses her own body as a gauge to measure her work, in the same way as a bird uses its body to gauge the size and form of its nest. The spider first spreads a thin coating of silk as a foundation, taking care to have this circular by turning round its body during the process. It then, in the same manner, spins a raised border round this till it takes the form of a cup, and, at this stage of the work, it begins to lay its eggs...
Página 369 - A pure cultivation thus obtained must, when introduced into the body of a healthy animal, produce the disease in question. 4. In the inoculated animal the same micro-organism must again be found (E.
Página 476 - The flora of the Coal Measures was the richest and most luxuriant, in at least individual productions, with which the fossil botanist has formed any acquaintance. Never before or since did our planet bear so rank a vegetation as that of which the numerous coal seams and inflammable shales of the carboniferous period form but a portion of the remains, — the portion spared, in the first instance, by dissipation and decay, and in the second by the denuding agencies. Almost all our coal, — the stored...
Página 505 - ... the larger petals. If the pigment be abundant, the cloudy torrent for the most part rushes off, and prevents our seeing what takes place; but if the atoms be few, we see them swiftly glide along the facial surface, following the irregularities of outline with beautiful precision, dash round the projecting chin like a fleet of boats doubling a bold headland, and lodge themselves one after another in the little cuplike receptacle beneath. Mr. Gosse, believing that the pellets of the case might...
Página 477 - Oolitic landscape, — we detect, in a few broken fragments of the wings of butterflies, decided trace of the flowersucking insects. Not, however, until we enter into the great Tertiary division do these become numerous. The first bee makes its appearance in the amber of the Eocene...
Página 60 - This angle is now determined by the arc of glass between the screens; thus we get an angle in glass the exact equivalent of the aperture of the objective. As the numerical apertures of these arcs are engraved on the apertometer they can be read off by inspection. Nevertheless a difficulty is experienced, from the fact that it is not easy to determine the exact point at which the edge of the screen touches the periphery of the back lens, or as we prefer to designate it, the limit of aperture, for...
Página 438 - ... individuals, which she multiplies with admirable promptitude to infinity. The remains of such minute animals have added much more to the mass of materials which compose the exterior crust of the globe, than the bones of Elephants, Hippopotami, and Whales.

Información bibliográfica