Proceedings, AAAS, Section B, 37,1888

ADDRESS

BY

PROFESSOR ALBERT A. MICHELSON.

VICE PRESIDENT^ SECTION B.

A PLEA FOR LIGHT WAVES.

It is no doubt universally conceded that no era in the world’s history lias ever seen such immense and rapid strides in the practical applications of science as that in which it is our good fortune to live. Especially true is this of the wonderful achievements in the employment of electricity for almost every imaginable purpose. Hardly a problem suggests itself to the fertile mind of the inventor or investigator without suggesting or demanding the application of electricity to its solution.

Do events in this fast age follow so rapidly that the delays of even the fastest express trains and steamers are unendurable — the remed}' is electricity. Is the labor of animals slow and expensive, or the carriage of the motive power itself, as well as its load, dusty, noisy and troublesome — the remedy is electricity. Are the barbarous tallow candle and the almost semi-barbarous use of gas for illumination totally inadequate to bridge over the hours of night— the remedy is electricity.

It would be wearisome to merely mention a tithe of the problems already solved or those on the eve of successful solution — nor is it at all necessary to insist on the richness of the harvest to be gathered by the successful experimenter in this fertile field.* Neither is it surprising that so many world-famous men should have de-

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SECTION B.

voted almost their whole lives to the pursuit of this most fascinating study.

In the enthusiasm aroused by so many wonderful, beautiful and bewildering results, such varfed and far-reaching discoveries in the vast fields of this subtile and powerful agent, it is not to be wondered at—or indeed entirely to be regretted—that possibly a great deal of attention has been diverted from the sister department of light. Undoubtedly, there have been man v important developments and improvements in optical instruments — the microscope, the telescope, the spectroscope and the camera may be said to lAve reached the point of practical perfection — and it is equally true that the observations and discoveries made with the help of these have more than justified the high expectations which their advent created. Certainly the wonderful impulse the study of biology has received by the revelations of the microscope; the enormous increase in our knowledge of the size, distance and motions of llie heavenly bodies, due chiefly to the little less than marvellous power and precision of our telescopes ; the knowledge of solar and stellar physics — which a few years ago would have been thought visionary if not impossible — attained by_#the spectroscope, now so happily supplemented by the camera; the insight gained into the structure of matter by spectroscopic interpretation of the messages which its molecules impart to the luminifeuous ether,—these are all even more truly wonderful and important than any^;of the astonishing marvels of electricity. But their original conception belongs to an era that is past*

If we except the exquisite results obtained in the manufacture and use of diffraction gratings and the very important work accomplished by the bolometer (a purely electrical invention, by the way), it may well be questioned whether, within the.last twenty years, there has been a single epoch-making discovery or inventi6n either in theoretical optics or in its applications.

It may, perhaps, be argued that the department of optics has been fairly completed ; that its theory (though still imperfect in many important points) has been fairly well developed and the range of its applications fairly well understood. Tlijg unexpected wonders it has already accomplished make it somewhat hazardous to reply that these same observations may noiv be applied to electricity and magnetism. Still it is safe to say that at any rate the more important facts and laws as well as the more promising lines