In cooler structures it becomes necessary in the dull season of the year to prevent the slopping of water over the plants or on the floor, as this tends to cause " damping off," - the stems assuming a state of mildewy decay, which not infrequently, if it once attacks a plant, will destroy it piece by piece.
Before explaining the advantages of such small damping it Will be necessary to consider the usual forms of the receiving appliance.
In length, which it is not, it is essentially based upon the supposition that the damping of the waves is negligible.
The damping off of seedlingsand in saturated soils not only are the roots and root-hairs killed by asphyxiation, but the whole course of soil fermentation is altered, and it takes time to sweeten such by draining, because not only must the noxious bodies be gradually washed out and the lost salts restored, but the balance of suitable bacterial and fungal life must be restored.
Pythium, which causes the damping off of seedlings, reducing them to a putrid mass in a few hours, and Phytophthora, the agent of the potato disease.
Grassot has devised a galvanometer, or " fluxmeter," which greatly alleviates the tedious operation of taking ballistic readings.2 The instrument is of the d'Arsonval type; its coil turns in a strong uniform field, and is suspended in such a manner that torsion is practically negligible, the swings of the coil being limited by damping influences, chiefly electromagnetic. The index therefore remains almost stationary at the limit of its deflection, and the deflection is approximately the same whether the change of induction occurs suddenly or gradually.
The weighing is conducted in the usual way by vibrations, except when the weight be small; it is then advisable to bring the pointer to zero, an operation rendered necessary by the damping due to the adhesion of water to the fibre.
It should be mentioned that the infra-red rays have a remarkable damping effect on the phenomena of phosphorescence, a fact which has.
Between loss and delay the spinner found an obvious alternative in damping the yarn artificially.
In these circumstances " syringing " and " damping down " are of value in cooling the temperature of the air in hothouses and greenhouses and increasing its humidity, thereby checking excessive transpiration.
The closing of ventilators (accompanied by syringing and damping of surfaces to produce a humid atmosphere) has for its object the conservation of as much solar heat as practicable.
The damping of all absorbent surfaces, such as the floors or bare walls, &c., is frequently necessary several times a day in the growing season, so as to keep up a humid atmosphere; hence the advantage of laying the floors a little rounded, as then the water draws off to the sides against the kerbstone, while the centre remains dry for promenaders.
In summer the temperature may range to° higher by artificial heat, night and day, and will often by sun heat run up to 90° or even 95°, beyond which it should be kept down by ventilation and frequent syringing and damping down of the pathways.
During the growing period the atmosphere must be kept moist by damping the walls and pathways, and by syringing the plants according to their needs; when growth is completed less moisture will be necessary.
Give auriculas and carnations abundance of air, but keep the roots rather dry to prevent damping off.
In the vinery and peach-house, attend to the keeping down of insects by syringing; and promote the growth of the young shoots, by damping the walls and paths morning and evening.
Continue the forcing of roses, hyacinths, &c. Houses containing large-flowered Japanese chrysanthemums will require to be kept dry, airy and moderately warm to prevent " damping-off " of petals.
Plant Houses, Frames, &c. - Carnations and picotees in pots must be kept rather dry to prevent damping off.
Peronosporaceae are a group of endophytic parasites - about ioo species - of great importance as comprising the agents of "damping off" disease (Pythium), vine-mildew (Plasmopara), potato disease (Phytophthora), onion-mildew (Peronospora).
Some forms cause damping off of seedlings - e.g.
An air-damping apparatus is attached in order to annul the natural oscillations of the pendulum.
Their prolonged literary activity - for some of them, like Grundtvig, were busy to the last - had a slightly damping influence on their younger contemporaries, but certain names in the next generation have special prominence.
The rotary presses in use at the present time are indeed wonderful specimens of mechanical ingenuity, all the various operations of damping (when necessary), feeding, printing (both sides), cutting, folding, pasting, wrapping (when required) and counting being purely automatic. These machines are of various kinds, and are specially made to order so as to cope with the particular class of work in view.