NO. 3 THE KAMPOMETER ABBOT 5 



meters. As the damping was very slight, the sensitiveness was almost 

 exactly proportional to the square of the time of single swing up to 

 2.0 seconds, which was the maximum we employed last autumn. 

 Probably this proportionality would have held closely to much higher 

 times of swing. 



We are now proposing to construct a kampometer of molybdenum 

 plated with cadmium. This combination gives about i^ times as great 

 temperature-bending tendency as brass-invar, and is nearly nonmag- 

 netic. We shall try different thicknesses of cadmium on molybdenum 

 of 0.005 millimeter thickness until we find the best proportions. We 

 shall use refined methods to give a perfectly straight and balanced 

 stem, and shall use the best modern magnet steel for the magnet 

 groups. This steel we believe will be not only of higher magnetic 

 susceptibility, but also will be more resistive to demagnetization than 

 that which we used last autumn. Thus we expect to be able to use 

 stronger controlling fields without reversing the magnetization of the 

 weaker of the two suspended magnet groups. In all these ways we 

 expect to increase the sensitiveness for a given time of swing, and 

 we expect to be able to control the system at 5 seconds single swing. 

 If so, we believe we may reach 1,000 times the sensitiveness which 

 we actually observed on August 11, 1932, with the first crude 

 kampometer. 



It will be noted that the kampometer has an advantage over both 

 the bolometer and thermopile, in that there is no appreciable escape 

 of heat from its sensitive part by metallic conduction. It has also an 

 advantage over the radiometer in that there is no appreciable escape 

 of heat by convection. Cooling only by radiation, it tends to assume 

 a higher temperature under illumination by a beam of radiant energy 

 than any of its three competitors. It lacks, of course, the capacity 

 to be inclined to any angle with the vertical, which is an advantage 

 of the bolometer and thermopile. With more robustly constructed 

 kampometers the quartz fiber might perhaps be replaced by a jewelled 

 bearing, and freedom for inclination to the vertical thus secured. 

 Various forms of the instrument will perhaps suggest themselves 

 to investigators. Anyone is at liberty to construct them as he pleases, 

 and I hope the kampometer may have a useful future. 



