In a refined form this method is often employed for measuring the intensity of a magnetic field at a given place, just as the intensity of gravity at different parts of the earth is deduced from observations of the rate at which a pendulum of known length vibrates.
The value in terms of arc of the scale of the record can be obtained by measuring the distance between the magnet mirror and the recording drum, and in most observations it is such that a millimetre on the record represents one minute of arc. The time scale ordinarily employed is 15 mm.
Instruments have been invented by Alvan Clark and Sir Howard Grubb for measuring with the spider-line micrometer angles which are larger than the field of view of the eyepiece.
It is roughly oblong in form, measuring about 80 m.
It is inferior in size only to the Colosseum and the amphitheatres of Capua and Verona, measuring about 153 by 130 yds.
But, Quite Apart From This, Electrical Methods Possess The Greatest Value For Calorimetry, On Account Of The Facility And Accuracy Of Regulating And Measuring The Quantity Of Heat Supplied By An Electric Current.
The large examples measuring from 6 to 9 or more in.
Electrolytic Meters are exclusively ampere-hour meters, measuring electric quantity directly and electric energy only indirectly, on the assumption that the pressure of the supply is constant.
This involves the introduction of machinery for measuring and controlling the speed at which it leaves the ship and for measuring the pull on the cable.
A bridge of this pattern has the advantage that the insertion or removal of a plug in the measuring arm does not tend to tighten or loosen all the rest of the plugs; moreover, there are fewer plugs to manipulate, and each plug is occupied.