effort, have been occupied in constructing during the last three or four centuries.

This reproach seems to me rather unjust. No one is able to destroy a scientific fact.

An electric current decomposes water into one volume of oxygen and two of hydrogen. This is a fact which will be true in the eternal future, just as it has been true in the eternal past. Ideas may perhaps change on what it is expedient to call electric current, oxygen, hydrogen, etc. It may be discovered that hydrogen is composed of fifty different bodies, that oxygen is transformed into hydrogen, that the electric current is a ponderable force or a luminous emission. No matter what is going to be discovered, we shall never, in any case, prevent what we call to-day an electric current from transforming, under certain conditions of combined pressure and temperature, what we call water into two gases, each having different properties, gases which are emitted in volumetrical proportions of 2 to 1.

Therefore, there need be no fear, that the invasion of a new science into the old will upset acquired data, and contradict what has been established by savants.

Consequently psychical phenomena, however complicated, unforeseen, or appalling we may now and then imagine them to be, will not subvert any of those facts which form part of to-day’s classical sciences.

Astronomy and physiology, physics and mathematics, chemistry and zoology, need not be afraid. They are intangible, and nothing will injure the imposing assemblage of incontestable facts which constitute them.

But notions, hitherto unknown, may be introduced, which, without casting doubts upon pristine truths, may cause new ones to enter their domain, and change, or even upset, our established notions of things.

The facts may be unforeseen, but they will never be contradictory.

The history of sciences teaches us, that their bulwarks have never been overthrown by the inroad of a new science.

At one time no notion of tubercular infection existed. We now know that it is transmitted by microbes. This is a new notion, teeming with important conclusions, but it does not invalidate the clinical table of pulmonary phthisis drawn up by physicians of other days. The discovery of Hertzian waves has in nowise shaken Ampère’s laws. Newton’s and Fresnel’s optics have not been changed into a tissue of errors because Rœntgen rays and luminous vibrations are able to penetrate opaque bodies. It appears that radium can throw out unremittingly, without any appreciable chemical molecular phenomena, great quantities of calorific energy; nevertheless, we may be quite sure, that the law of conservation of energy and thermo-dynamic principles will remain as true now as ever.

Likewise, if the facts called ‘occult’ become established, as seems more and more probable, we need not feel anxious as to the fate of classical science. New and unknown facts, however strange they may be, will not do away with old established facts.

To take an example from Dr. Maxwell’s work, let us admit that the phenomenon of raps—that is to say, sonorous vibrations in wood or other substances—is a real phenomenon, and that, in certain cases, there are sounds which no mechanical force known to us can explain, would the science of physics be overthrown? It would be a new force thrown out on to wood, etc., exercising its power on matter, but the old forces would none the less preserve their activity, and it is even likely that the transmission of vibrations by means of this new force would be found to be in obedience to the same laws as those governing the transmission of other vibrations;—the temperature, the pressure, the density of air or wood would continue to exercise their usual influence. There would be nothing new, save the existence of a force until then unknown.

Now, is there any savant worthy of the name who can affirm, that there are no forces, hitherto unknown, at work in the world?

However impregnable Science may be when establishing facts, it is miserably subject to error when claiming to establish negations.

Here is a dilemma, which appears to me to be very conclusive in that respect:—Either we know all Nature’s forces, or we do not. Now the first alternative is so ridiculous, that it is really not worth while refuting it. Our senses are so limited, so imperfect, that the world slips away from them almost entirely. We may say it is owing to an accident, that the magnet’s colossal force was discovered, and if hazard had not placed iron beside the loadstone, we might have always remained ignorant of the attraction which loadstone exercises upon iron. Ten years ago no one suspected the existence of the Rœntgen rays. Before photography, no one knew that light reduces salts of silver. It is not twenty years since the Hertzian waves were discovered. The property displayed by amber when rubbed was, until two hundred years ago, all that was known of that immense force called electricity.

Question a savage—nay a fellah or a moujik—upon the forces of Nature! He will not know even the tenth part of such forces as elementary treatises on physics in 1905 will enumerate. It appears to me that the savants of to-day, in respect to the savants of the future, stand in the same inferiority as the moujiks to the professors of the college of France.

Who then dare be so rash as to say that the treatises on physics in 2005 will but repeat what is to be found in the treatises of 1905? The probability—the certainty, one might say—is that new scientific data will shortly spring up out of the darkness, and that most powerful and altogether unknown forces will be revealed. Our great-grandchildren will be amazed at the blindness of our savants, who tacitly profess the immobility of science.

If science has made such progress of late, it is precisely because our predecessors were not afraid to make bold hypotheses, to suppose new forces, demonstrating their reality by dint of patience and perseverance. Our strict duty is to do likewise. The savant should be a revolutionist, and fortunately the time is over when truth had to be sought in a master’s book—magister dixit—be he Aristotle or Plato. In politics we may be conservative or progressive; it is a question of temperament. But when the research of truth is concerned we must be resolutely and unreservedly revolutionary, and must consider classical theories—even those which appear to be the most solid—as temporary hypotheses, which we must incessantly check and incessantly strive to overthrow. The Chinese believed that science had been fixed by their ancestors’ sapience; this example contains food for meditation.

Moreover—and why not proclaim it loudly—all that science of which we are so proud, is only knowledge of appearances. The real nature of things baffles us. The innermost nature of laws governing matter, whether living or inert, is inaccessible to our intelligence. A stone tossed up into the air falls back again to the earth. Why? Newton says through attraction proportional to bulk and distance. But this law is only the statement of a fact; who understands that attractive vibration, which makes the stone fall? The fall of a stone is such a commonplace phenomenon, that it does not astonish us: but in reality no human intelligence has ever understood it. It is usual, common, accepted; but like all Nature’s phenomena without exception it is not understood. After fecundation an egg becomes an embryon; we describe as well as we can the phases of this phenomenon; but, in spite of the most minute descriptions, have we understood the evolution of that cellular protoplasm, which is transformed into a huge,