Professor Trowbridge's Lecture.

Professor Trowbridge by invitation of the Harvard Electrical club delivered an interesting lecture last night in the Jefferson Physical Laboratory on the nature of electricity. He wished to call attention, the lecturer said, to a few experiments which have been made in German laboratories during the last two years with a view to illustrating a great electrical principle. The two great generalizations of the last two hundred years, the laws of gravitation and of the conservation of energy, have both originated in England. In fact all great advances in the domain of Physics have been made by Anglo-Saxons. The German experiments of the last two years only serve to illustrate the great principle enunciated ten years ago by Clerk Maxwell, namely, that heat, light, and electricity are all one and the same thing, and that we receive them all by electro-magnetic impulses transmitted through the ether from the sun. In the last one hundred years our ideas on physical subjects have immensely advanced. Benjamin Franklin's machine for producing electricity is a hundred times as large as the one we use today, yet ours is a hundred times as powerful. The electric light used to be seen only on the lecturer's table, but now his thunder has been stolen by the practical men of the day, and electricity lights our streets. The German experiments are almost microscopic, though the conclusions drawn from them are enormous.

Benjamin Franklin looked at the skies a hundred years ago to discover the nature of electricity, and we are doing the same thing now. What Franklin failed to see was that the discharge of electricity is not in one direction, but oscillatory. Josepe Henry noticed in 1835 that a Leyden jar gave out not one spark merely but several in succession. He discovered induction, and surmised wave motion, but he never thought of looking together for the source of that motion. It never occurred to him nor to us until very recently, that the electricity is not in the wires of an electrical apparatus, but in the outside air. The discovery of this fact is the great achievement of recent science.

At this point Professor Trowbridge performed some interesting experiments, and showed some equally interesting photographs to prove the existence of waves of electricity and their oscillatory motion. He then made a most significant experiment in induction, and explained how a man killed by an electric wire was in reality struck by lightning. A dozen lectures would be necessary to explain all the aspects of those phenomena, and only a short description of them was attempted in last night's lecture.