|
|
Of miles the wind travels in a certain time.
The chart of the anemoscope is fixed on a cylinder which revolves before a pen controlled by clockwork. The paper inscribed with the cardinal points and the hours move with the wind.
To obtain the force of the wind, the wind is permitted to beat on a metal drum suspended by chains from a frame. The pressure upon the drum conveyed downward through a guide-rod pulls a spring to which the pen is attached upon the chart, drawn aside by clockwork at the rate of one half an inch in an hour. The force is written expressed in pounds weight per square foot.
Since "the main distinguishing feature of a storm is the movement of the air, the pressure of the wind," such instruments as the above are indispensable to the symptomology of the weather.
For priority of age and weight of general influence, perhaps the barometer should have been first named. In the recording room it occupies a conspicuous position beside the great round disc of the air thermometer. The sun thermometer is appropriately placed over against the pluviometer, its long pen-arm more active to-day in registering the hours of sunshine than is now the empty bucket of the latter— the "rain measurer."
The electrograph stands on a table by itself, receiving the admiration it deserves for its exquisite adjustment to a most delicate task. The electric potential of the air is obtained by means of a water-dripping apparatus, a tank of galvanized iron on the roof, with a projecting pipe letting fall the water in drops. Traversing this column of water back to the tank, the electricity of the air gives the tank its own potential. An insulated wire carries this potential to the electrometer, whose quivering, oar-shaped needle is reflected by a mirror, and this reflection photographed upon the sensitized paper of the electrograph.
Thus are recorded the varying conditions of the atmosphere. Three times a day, at seven in the morning, at two in the afternoon and at nine in the evening, observations are taken. The data recorded on the weekly charts are reduced to means, and from the daily means a monthly summary is prepared. At the end of the year an annual summary is deduced from the monthly summaries. The highest and lowest readings are recorded as maxima and minima. By the accumulation of readings and by their reduction, the ranges of temperature and the deviations of rainfall are determined. For it is not the temperature or the atmospheric pressure of the wind velocity for an hour or a day which renders a place habitable or uninhabitable for crops or man, but its average climatic conditions.
The observer must be a historian before he can be a prophet, and he must have an accurate acquaintance with the reports of other stations in addition to those of his own. He must have with them the close connection of the telegraph wire, in order to be beforehand with the changes. The arrangements for such telegraphic communication have already been made at Amherst, and now the signal flags with their warning marks and colors are added to the cylinder, the drum and the tank, the arrows and the cups.
In the early days of the Agricultural College, Prof. Stockbridge, afterwards president of the college, prepared some interesting experiments with what he called a lysimeter, investigating the phenomena of dew and the percolation of the soil. For these experiments, carefully and scientifically carried out, the resources were obtained by the sale of a fertilizer of his own manufacture.
In its first phase, the experiment station was an instance of spontaneous generation. In its latest phase, in the evolution of commodious buildings and complete equipment, the encouraging attitude of the world toward agricultural investigation is clearly demonstrated.
-- page 80 --
|
These pages are © Laurel O'Donnell, 2005, all rights reserved
Copying these pages without written permission for the purpose of republishing
in print or electronic format is strictly forbidden
This page was last updated on
12 Sep 2005
|