=Which is the Fittest to Survive?=--Prof. A. W. Rücker spoke in his opening address at the recent meeting of the International Magnetic Conference in Bristol, England, of what seems to be a law of Nature, that the products of an organism are fatal to itself; in accordance with which, he said, pure science is threatened by the very success of its practical applications. The smoke of our cities blots the stars from the vision of the astronomer, and now the science of terrestrial magnetism is threatened by the artificial earth currents of the electric railway. Prof. W. E. Ayrton, in his welcoming address, took another view of the subject and answered the reference the electrical engineers make to the principle of the survival of the fittest when they are told of the ruin their wires are bringing upon magnetic observatories--"So much the worse for the observatories"--"Can the system of electric traction that has already destroyed the two most important magnetic observatories in the United States and British North America be the best and fittest to survive? Again, do we take such care and spend such vast sums in tending the weak and nursing the sick because we are convinced that they are the fittest to survive? May it not be perhaps because we have an inherent doubt about the justice of the survival of the strongest, or perhaps because even the strongest of us feels compelled modestly to confess his inability to pick out the fittest, that modern civilization encourages, _not_ the destruction but the preservation of what has obvious weakness, on the chance that it may have unseen strength? When the electrical engineer feels himself full of pride at the greatness, the importance, and the power of his industry, and when he is inclined to think slightingly of the deflection of a little magnet compared with the whirl of his one-thousand-horse-power dynamo, let him go and visit a certain dark storeroom near the entrance hall of the Royal Institution, and while he looks at some little coils there, ponder on the blaze of light that has been shed over the whole world from the dimly lighted cupboard in which these coils now lie. Then he may realize that while the earth as a magnet has endured for all time, the earth as a tramway conductor may at no distant date be relegated to the class of temporary makeshifts, and that the raids of the feudal baron into the agricultural fields of his neighbors were not more barbarous than the alarms and excursions of the tramway engineer into the magnetic fields of his friends."