eye become through their use that it is not great exaggeration to say that one may now have a disordered eye repaired, corrected, and set going with little more uncertainty than attends the performance of the same duty for an ill-conditioned chronometer. Had Helmholtz accomplished nothing except the invention of these instruments, he would have been entitled to the thanks of all mankind, on account of the comfort they have added to life and the pain and suffering they have prevented. If I had devoted all of the time allotted to me to a simple enumeration of the contributions to human knowledge made by Von Helmholtz during fifty years of marvelous intellectual activity, I must have left my task incomplete; but I must not close without reference to one or two of these, more purely physical in their character and equally stamped with the genius of their author. Perhaps Nature has shown herself most reticent and unyielding when scientific men have questioned her as to the ultimate structure of matter, the full knowledge of which includes a satisfactory explanation of the force of gravity, which is one of its essential properties. Hypotheses which have been very useful in their time have been finally rejected because they involved some impossible conception, such as action at a distance, which was for a long time believed possible. The tendency is now and has long been to regard space, or at least that part of it in which we have any particular interest, as a plenum, and to assume a continuous, incompressible, frictionless elastic fluid in which and of which all things are. In the development of his exquisite theory of vortex motion, Helmholtz demonstrated the possibility of a portion of such a fluid being differentiated from the rest in virtue of a peculiar motion impressed upon it, and that v hen so differentiated it must forever remain so, a fact which was quickly seized upon by Lord Kelvin as the foundation of a vortex theory of matter, thus sharing with Helmholtz the honor of having approached nearer than all others to the solution of the great mystery. From the genesis of an atom to the origin of the universe seems a long step, but it is not too great for the intellect of man. The wellknown nebular hypothesis was advanced long before Helmholtz's time, but a better knowledge of thermodynamics had quite upset one of its generally accepted principles, namely, that the original nebulous matter was fiery hot. As long ago as 1854, Helmholtz showed that this was not a necessary assumption, and proved that mutual gravitation between the parts of the sun might have generated the heat to which its pres ent high temperature is due. The greatest philosophers of the past hundred years have attempted to account for this high temperature and for its maintenance, on which all life on this globe depends. The simple dynamical theory of Helmholtz has survived all others, and is to-day universally accepted. But I must cut short this absolutely inadequate account of what the scholar did, that I may say a word or two of what the man was. Although one of the most modest and quiet of men, no one could meet him without feeling the charm of his personality. While he bore a dignity which became the great master of science which he was everywhere admitted to be, he was approachable in an extraordinary degree. He was eloquent in popular address and believed in the obligations of men of science to the general public. In scientific discussion, whether on his feet or with pen in hand, there was a certain massiveness about his style and manner which was generally irresistible. In his attacks upon the region of the unknown he showed possibly less brilliant strategy than one or two of his contemporaries, but he rarely, if ever, found himself obliged to conduct a retreat. In 1893 he was selected by the Emperor as the head of the German delegation, five in number, to the International Electrical Congress held in Chicago in August of that year. His more than three score and ten years weighed upon him, and he begged to be relieved of the duty. The young Kaiser, who was fond of him and who loved to honor him in every way, sent for him. On hearing his modest plea, he said, "Helmholtz, you must go; I want the Americans to see the best I have of every kind, and you are our greatest and best man." As becomes a dutiful subject he yielded. While in this country every honor was shown him. Here he found many of the hundreds and thousands of his pupils who everywhere in the world are adding luster to his name by perpetuating his spirit and is methods, and all were ready to serve him. Electrician, mathematician, physiologist and physicist, he found everywhere a large and ppreciative constituency, while his own almost boyish pleasure in whatever he saw that was novel, was charming to see. On his homeward voyage he met with an accident which was thought by many to be the beginning of the end. Up to the time of his death, which occurred about a year later, he continued, but not very actively, to direct the great institution for original research, in which, by the wisdom of an appreciative Government, he had found full scope for his His interest in the important work done at the Chicago Congress continued through this year, and one of the few long letters he wrote had reference to its proceedings. On the 8th of September, 1894, e died, and on the 13th he was buried at Charlottenberg, princes and peasants alike mourning his loss. Dowers. Von Helmholtz occupied so large a part of the scientific horizon and for so long a time that we have not yet become accustomed to his bsence. But it is not too soon to agree that the following admirable ines which appeared in the London Punch a little more than a year go express in some measure our judgment of the man and his work: "What matter titles? Helmholtz is a name That challenges alone the award of fame! |