Had it told us that for long ages the earth was the abode of no nobler creatures than reptiles, how speedily and indignantly would philosophy have resented the insult to divine wisdom?

It has been common in this discussion to remind us that Christianity has always been the enemy of scientific progress. This is no more true of Christianity than it is true of science itself. Every innovation is opposed by those who have become wedded to old forms of belief. Men are always unwilling to acknowledge that they have believed an error. The Galileos, the Columbuses and the Harveys have encountered alike the opposition of the churches and the schools of science. And when we remember how many false theories have been proposed for every one that has survived the test of time and further investigation, we can neither wonder at the existence of this spirit, nor regret it, though we may deprecate the manner in which it has sometimes found expression. The world cannot help remembering how frequently men who have made some discovery in itself valuable, have supposed themselves to have found the key of all mystery, and proceeded to construct upon it some universal theory of genesis and destiny, and asking how large a proportion of these theories have survived, unmodified, the life of their author?

Vast as have been the achievements of science, the mystery of the universe seems vaster than ever. A little knowledge has been hewn from the infinite unknown. The larger the sphere of knowledge becomes, the more of the unknown does it touch. Every answer suggests many more queries we cannot answer. We think then it cannot be the scientist that would have us believe the universe has no room for a power he has not traced.

Christianity and science are alike in search of truth. Alike they encounter mystery at every turn. Alike they will be embarrassed and dishonored by those who misconstrue or misapply them. Alike they will often fall into error. May they learn more and more to recognize the beauty and the worth of each other, and the wisdom and goodness of the great Author. While we revere science, we would still worship God.

ARTICLE II-MODERN PHYSICAL DISCOVERIES AND THEIR LIMITATIONS.

IF two pieces of metal-for instance, bismuth and antimony -be united by their ends and the place of contact heated, a current of electricity will be generated. The heat, as such, disappears in this case, and by some unknown process becomes converted into, and reappears in the form of, electricity. This electricity may then be conducted along wires laid parallel to the direction of a magnetic needle, and that needle will at once turn itself into a line, at right angles with that of its former position. Here we have electricity producing, or causing, mechanical motion. If now the electric current be conducted around a piece of bent iron, the iron becomes magnetic. Here we have electricity producing magnetism. If then the current be conducted through or along a wire of platinum, that wire will become heated, to the degree of giving off a brilliant light. Here we have electricity producing light. If, finally, the current be conducted through a chemical solution of some salt, or other compound, the compound will be decomposed, and its elements will either appear at the ends of the conducting wire or enter into new combinations, according to the conditions.

Thus with heat as the initial force the entire list of physical forces, as now known, may be made to appear in succession; electricity; magnetism; mechanical motion; light; and chemism; by fulfilling certain conditions. Hence it appears that heat, light, electricity, mechanical motion, magnetism, and chemism are so intimately related that they produce each other or may be resolved or transformed into each other. This is what is meant by the term "Correlation of Forces."

But this law includes yet more than this. Not only will any one of these cause or produce the rest, but the quantity of resulting forces produced by the given initial force of the series is fixed and constant. If one unit of heat be applied at the junction of the metals, a certain fixed quantity of electricity is always generated. This in turn will produce another fixed

quantity of magnetism, and so through the entire series. If the initial heat be doubled, the resulting quantities of all the others will be doubled: or, if but half a unit of heat be applied, then but half the resulting quantities of the other forces will be produced. This completes the law of Correlation.

What is called "Conservation of Force" is only a form of this quantitive side of "Correlation." The idea of "Conservation" is simply this: no force is either created or annihilated in any of the manifold processes of the universe; but only transformed. When the blow of a hammer is arrested on an anvil, the force of the hammer's motion is not destroyed, as it seems to be, but is transformed, mainly into heat. And it produces an increase of heat in the anvil, sufficient, if properly applied, to raise the hammer to the exact height from which it fell in the blow. When a moving train is brought to rest, the mechanical motion of the train and its momentum are not destroyed, as they appear to be, but they are converted into heat by the action of brakes and track; and into an amount of heat such, that, could it all be placed back again in the boiler so as to act as steam, and be thence applied, it would restore the train to the exact degree of its lost velocity and momentum.

And so always. Whenever any form of force disappears it is not destroyed, but only gives place to an equivalent amount of some other form of force, perhaps less obvious, but always equally potent.

So too, as there is no such thing known as annihilation of force, there is no such thing as its creation. But wherever any form or result of force appears it is derived from some preceding, though perhaps concealed, force, of which it is the exact equivalent. This is what is meant by "Conservation of force."

Passing out of the inorganic into the organic world, these principles of Conservation and Correlation hold good in both branches of it, vegetable and animal. A tree is no less a product of physical forces than a house. Nothing less than a given and exact amount of physical force, actually put forth in preparing, combining and fixing its parts, will produce a house. Exactly so with a tree. It has been rather loosely held that all the power used in building up a giant oak, for instance, was originally locked within the producing acorn. A directing and

appropriating force unquestionably is held within the acorn, but no more; and from germination through to its latest hour that tree uses the physical forces, heat, light, etc., which it somehow appropriates from the sunbeam, in carrying on all the processes of its life and growth. How it seizes them we do not know; whether they are used by the plant under any of the forms known to us, heat, light, etc.; or, under others better adapted to the plant's needs, but unknown as yet, we cannot tell. But that they are the agencies of the tree's upbuilding no one that is informed now doubts. When a tree is cut down, chopped up, and burned within our stoves, the light and heat given out in the process is the exact measure of those used in that tree's upbuilding, which are thus again liberated and pass back into the universe whence they came.

So also in the highest department of the organic world, the animal, including the body of man. All the vital processes of animal life, nutrition, growth, action, are carried on by means of transmuted physical force. The heat of the animal body is simply the heat of the food it consumes; liberated within it by a process entirely similiar to the burning of so much material outside of the body.

As regards nerve force, however, there is yet some obscurity. It has been proved that it moves only at the rate of ninety-seven feet per second, a speed equalled by the greyhound and racehorse in instances. A close connection is, however, believed to exist between nerve force and electricity. Electricity has never been shown to be transmutable into nerve force, yet it would be rash to affirm that it is not so transmutable. An electric current through the nerve causes contraction of the muscle; while a diminution of the normal electric current of the nerve will do the same. Prof. Barker thinks that electricity and nerve force bear a relation to each other analagous to that existing between electricity and magnetism.

Even in the high domain of thought this correlation has been sought; some say found. The thermo-electric pile, an instrument made of alternate bars of bismuth and antimony, and connected by a wire with a magnetic needle, will show and measure an amount of heat quite too small for the power of any thermometer. If this instrument be placed on the hollow of

the skull, just above the occipital protuberance, and so connected that it shall only register changes of the temperature due to thought or emotion, as can be done, remarkable phenomena appear. Prof. Barker says: "By long practice it was ascertained that a state of mental torpor, lasting for hours, could be induced, in which the needle remained stationary. But let a person knock on the door outside the room, or speak a single word, even though the experimenter remained absolutely passive; and the reception of the intelligence caused the needle to swing through twenty degrees." And he adds in explanation : "No conversion of energy is complete, and as the heat of the muscular action represents force which has escaped conversion into motion" in the muscle, "so the heat evolved during the reception of an idea is energy which has escaped conversion into thought, from precisely the same cause."

Such is a brief statement of what is included under present ideas of the conservation and correlation of the physical forces; and of the ramifications of these forces into vital processes. Let us now take a view of some of the limitations which may be discerned in this matter.

1. Without mentioning other things that might be urged, it may first be noted that Gravity is a force that has refused, wholly refused, to come under these laws of correlation and conservation. There is no known way of conditioning heat, light, electricity, magnetism, or chemism, so as to get a result in the form of gravity, if the expression be allowed. Neither can we so condition gravity as that it will disappear in any case and produce any of these forces by its transmutation. It need not be said that this never will be done. But it is certainly true that no perceptible approach has been made toward doing it.

Take the case of a weight lifted and then let fall. At first view it might seem that the heat developed by its stoppage was a conversion of gravity. But it is not so. That heat is the exact measure of the force that lifted the weight; and if it were all applied again, it would lift it to the exact place whence it fell. But, throughout, the force of gravity undergoes neither change of form nor diminution of intensity in this case. Gravity acted while the weight was being lifted; while it was