1879-1 
Proceedings of Societies. 
583 
is a misnomer, and that what was really measured by Lamansky 
and Tyndall was the energy absorbed by the lampblack and the 
absorption due to the prisms used. He considered that there 
was no inherent heat in the speCtrum. He found that Dr. 
Draper had not taken into account the amplitude. 
Prof. Guthrie said that Captain Abney had expressed what 
many thought — namely, that heat was radiant energy. 
Mr. Grant then described an investigation which he had made 
into the induction lines round two parallel coils of wire in the 
primary coil, an intermittent current of electricity from a 
Leclanche battery flowed ; and in the secondary, a telephone 
was connected up to deteCt the induction sounds. With this 
apparatus he found that with the coils kept parallel to each 
other there were lines, or rather a surface of minimum induction, 
surrounding the primary, and that if the secondary were placed 
in these lines hardly any induction noise could be detected. A 
diagram, representing a medial section through the coils, showed 
the lines to proceed from the wire of the coils in two curves 
resembling parabolas, one from each cross seCtion of the wire 
outwards. 
Dr. Shettle then described his experiments proving the lines of 
force in a bar magnet to run spirally round the bar between the 
equator and poles, the equator being decentred and oblique across 
the bar, as shown by diagrams. 
Prof. Rowland, of Baltimore, made some observations on the 
new theory of terrestrial magnetism of Profs. Ayrton and Perry 
(see “ Monthly Journal of Science,” 3rd series, vol. i., p. 287). 
He said the experiments on which the theory was founded had 
been attributed to Helmholtz, but they were entirely his own, he 
having gone to Berlin to make them. The new theory had 
occurred to himself on making these experiments, but he had 
rejected it because he found that the potential which the earth’s 
surface would require to have would not only cause violent 
planetary disturbances, but by mutual repulsion drive objects off 
the earth. He had made also an experiment to see if absolute 
motion of electricity would cause magnetisation, but failed to get 
any effeCt from it. Then he resorted to calculation to find the 
magnetic effeCt of relative motion by rotation of a changed sphere 
of perfeCt magnetic permeability that is more magnetic than 
iron. He found that when the sphere was uniformly charged and 
rotating there would be a magnetic field in its interior ; but, 
instead of the result of Messrs. Ayrton and Perry, that if the 
earth were charged to a potential of, he believed io 8 volts rela- 
tively to interplanetary space, the earth’s magnetism would be 
what it is, he found the necessary charge to be 61 + 10^ volts. In 
the ordinary atmosphere this potential would produce a spark 
nine million miles long, and discharge across to the moon. If 
the moon were electrified to the same degree, the mutual repul- 
sion would overcome the force of gravity between them. He 
