Retrospect of Philosophical, Mechanical, Chemical, and Agricultural Discoveries, Volumen8

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J. Wyatt, 1815
 

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Página 215 - ... beneath, and the slender bar of wood. A plant of the same species was placed at the east end of the house, near the glass, and was in some measure skreened from the perpendicular light ; when its tendrils pointed towards the west, or centre of the house, as those under the preceding circumstances had pointed towards the north and back wall. This plant was removed to the west end of the house, and exposed to the evening sun...
Página 36 - ... of pines ; these again, forming themselves into festoons of white feathery smoke in the most fanciful manner imaginable, intermixed with the finest particles of falling ashes, which at one time assumed the appearance of innumerable plumes of black and white ostrich feathers surmounting each other ; at another, that of the light wavy branches of a weeping willow.
Página 217 - ... plants were trained almost perpendicularly downwards; but with an inclination of a few degrees towards the north ; and the tendrils of these permanently retained very nearly their first position, relatively to their stems; whence it appears that these organs, like the tendrils of the ampelopsis, and the claws of the ivy, are to a great extent under the control of light. A few other plants of the same species were trained in each of the preceding methods ; but proper objects were placed, in different...
Página 218 - ... matter of the plant upon the one side, than upon the other. The external pressure of any body upon one side of a tendril will probably drive this fluid from one side of the tendril, which will consequently contract, to the opposite side, which will expand ; and the tendril will thence be compelled to bend round a slender bar of wood or metal, just as the stems of germinating seeds are made to bend upwards, and to raise the cotyledons out of the ground ; and in support of this conclusion I shall...
Página 215 - ... reach of its tendrils ; and to this substance they soon appeared to be strongly attracted. The paper was then placed upon the opposite side, under similar circumstances, and there it was soon followed by the tendrils. It was then removed, and a piece of plate glass was substituted ; but to this substance the tendrils did not indicate any disposition to approach. The position of the glass was then changed, and care was taken to adjust its surface to the varying position of the sun, so that the...
Página 217 - ... any disposition to approach the points, from which they once receded. The tendrils of the vine, on the contrary, varied their positions in every period of the day, and after returned again during the night to the situations they had occupied in the preceding morning ; and they did not so immediately, or so regularly, bend towards the shade of contiguous objects. But as the tendrils of this plant, like those of the ampelopsis, spring alternately from each side of the stem, and as one point only...
Página 17 - Another principle consists in the operation of the ends of piston-rods, proceeding from the opposite extremities of the cylinder ; on the outside of the rim of a large wheel, whose centre is placed at the distance of about half the stroke of the piston from the axis of the cylinder. The rim of the wheel projects so as to extend to the line of the...
Página 330 - Three other grooves were added successively opposite one another, so as to divide the piston into four equal parts; and still the spunk took fire. When the grooved piston is moved backwards and forwards in the tube, the air may be heard entering or issuing out ; and the friction is so slight, that the effect of the instrument is easily obtained by push. ing it with the hand. This kind of piston would be preferable to those that fit accurately, if a solid substance were employed, hard enough to resist...
Página 216 - ... and ivy, as soon as they exceeded the height of their supports, inclined many points from the perpendicular line, in the opposite direction. It appears therefore that not only the tendrils and claws of these creeping dependent plants, but that their stems also, are made to recede from light, and to press against the opake bodies, which nature intended to support and protect them. M.

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