"Then," said I, "to take the amount of exercise recommended, I must go up such a hill fifteen times in a day?"

"That is just it," said the Doctor; "only of course you would do some work in coming down again, which would have to be taken into account."

"I am sure I am very much obliged to you for the explanation," said I. "But I don't see how the work done is measured. You can't weigh everybody, and measure how high they climb in a day."

"It would be rather a tedious process," said the Doctor. "But I can tell you how work is measured. It can either be measured in foot-tons, or in foot-pounds, which is a more usual unit; or it can be measured in units of heat."

"I know working hard makes one hot," said I; "but how heat is to be measured, or is to measure work, beats me hollow."

'Nothing is more simple," said the Doctor. "The discovery was made by Dr. Joule, but it has been tested by many other scientific men here and in France, and we are all there or thereabouts. What is called a Joule's Equivalent, or a British unit of heat, is that quantity of heat which would raise one pound of water one degree Fahrenheit in temperature. And that same quantity of heat, if turned into work, would raise 772 pounds one foot. It would do 772 foot-pounds of work."

I was still rather perplexed at this idea, new to me, of heat doing work. But at that moment I heard the rapid snorting of a locomotive, as of some gigantic animal labouring with its load, and the idea seemed to flash into my mind, "Is that what works the locomotive ?" asked I.

"Indeed it is; that and nothing else," replied the Doctor.

"But I thought that was steam ?" said I.

"Vaporising water," said my companion, "or raising steam, is one of the most convenient modes of applying the heat released from coal by combustion to effect work. But it is the heat that does the work; and that in the proportion I tell you."

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Ah," said I, "I should have taken much interest in scientific matters if I had had the advantage of learning them. But they were not taught when I was a boy, except, I suppose, to engineers and that kind of people. Really I am glad to fall in with you, your conversation seems to open one's mind. Then, I suppose," added I,

for the subject quite took hold of my imagination-" that that is just the difference between the steam horse, as we call it, and a live horse? The steam horse moves by heat."

"Yes," said the Doctor, "and the live horse too."

"Oh! the live horse moves himself," said I; "that is because he is alive."

"Then," you will be surprised if I tell you," said the Doctor, "that the live horse, or the live man, moves exactly as much by the conversion of heat into work done as the locomotive does."

"I can't see that," said I. "And the man?' why look!"-and I gave a little bound into the air—" I do that of my own will. It is my spirit that causes me to leap-not heat-why, it makes me hot to do it."

"All those ideas about spirit," said the Doctor, "are survivals of the old theological theory, which has been entirely abandoned by all educated men.'

"You surprise me," said I-as he looked very steadily and solemnly at me "you don't mean that educated men-that you for

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"No such things?" asked I, no such things as what?"

"No soul-no future life," said he. "What you call God is the substantia of Spinoza-a mere general term for the totality of phenomena. You and I are as much machinery as the locomotive; and shall be taken to pieces like it when our work is done, and the pieces used up for other purposes."

"I am sure you cannot be joking," said I; "but really that seems to me a very terrible idea."

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"Why so?" said he. "On the contrary, look at the old theological notions. They were terrible, if you like. What did they not

threaten you with ?"

"But," said I, "if there wereif there could be any truth in what you say, would not the consequences be dreadful ?"

"How ?" asked he.

"If you take away the idea of a future life, and a future condition depending on the use made of this life, do you not relax all the social bonds? do you not take away all that enforces right action ?"

"The wise man," said the Doctor, "will do what he thinks right because he thinks it is right-not because he is bribed to do it, or threatened if he does not."

"Well," said I, "I am not competent to argue with you. The subject is so new to me, and evidently so familiar to you. But what you have said troubles me very much. How can you know, for instance, that I have not a soul ?"

"I can prove that to you very easily," said the Doctor. "Can you take out of a bag more than you have put into the bag?"

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No," said I.

"At least, not more than there is in the bag. But I may not know what is there, or who put it in."

"Just so," said the Doctor. "Now, you are the bag, and I can tell exactly what has been put in to make you move, and feel, and think."

I am afraid I did nothing but stare at my companion. I felt quite flabbergasted.

"All organic matter," said the Doctor, "consists, in the first instance, of a substance called protoplasm. Certain mineral substances are also employed in the structure of the skeleton; but I am speaking of the tissues; the nerves, which are the most important, and the muscles, and the veins, and the blood. Well, all these are only more or less modified forms of

protoplasm. And all protoplasm is composed of carbonic acid, water, and ammonia, which are themselves composed of the elementary substances, as we call them, carbon, oxygen, hydrogen, and nitrogen. All living things, then, are made of these chemical elements, so that we know exactly what is put into the bag."

But," said I, "does that prove that there is nothing else there ?"

"What should put anything else there?" said he.

"I may not be able to reply; but I don't think that that proves that there is not something else," said I.

"Very fairly argued," said the Doctor; "then there we come back again to what I was telling you about Joule's Equivalent. Until that discovery of the conversion of heat was made I could only have said, 'I see no evidence of what you call a soul.' Now I go a step further in fact, the whole way further. I prove that there is no soul, by ascertaining exactly the source of all vital phenomena. I can measure all the work you do in the day in foot-pounds, and I can tell you to one foot-pound whence comes the heat required to do the work."

"That seems very strong, I must admit," said I.

We can

"We can arrive at the same result, pretty closely, by two different ways," said he. "First of all by observation-a long series of observations; on armies, hospitals, schools, all sorts of great collections of men or women. ascertain exactly the average amount of food required to support life, and to enable the train, for instance, to travel so many miles. We can find how much heat is produced by the combustion of that amount of food; and we find that that is exactly equal to the work done."

"And what is the other mode?" asked I.

"We can ascertain the amount of air that passes through the lungs in a day-and how much of the oxygen of the air is converted into carbonic acid in the lungs; and we thus know the quantity of heat due to that consumption of oxygen. And we find that to tally exactly with the other calculation."

"When you say combustion,"

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'Exactly," said the Doctor; "if you take more food than you consume by work, you grow fatter or heavier. If you increase your exertion in the day, or diminish your quantity of food, you consume more than you assimilate. You burn more fuel than you put into the tender, and the tender becomes lighter in consequence."

"So you put it this way, if I understand," said I; “ you account for all my motion by the combustion of the food which I have eaten, and which has been first converted into my tissue, and then burnt in me in producing this motion."

"That is just it," said he.

"And you find, over a long series of experiments, the balance to be exact between the food consumed and the work done; and you also find the balance to be right between the oxygen taken into the system and the heat produced, converted into work done."

"Really, you do credit to my teaching," said the Doctor; "I could not have expressed myself more exactly."

"I suppose, then," said I, "that, as you know so exactly what this protoplasm is, and how it is used to build up living creatures, you can readily make it."

that."

If they are

warmed, and kept at a certain heat for a certain time, they become formed into a bird."

"That is just so. You see an instance of the power of heat."

"I understand that heat is essential to the process of forming the chick in the egg. But it seems to me that there must be something more. You know the exact chemical composition of the egg. Now, if you make that composition, chemically, and warm it, and keep it warm, you do not produce a chick."

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No, we do not."

"Then it seems to me, on your own showing, that there is something taken out of the egg which you don't put in—which you can't put in to your artificial egg, and without which the real egg becomes addled."

"The heat you mean."

'No, I do not. I think there is a something else a something that you cannot put in. Heat you can put in; but heat is of no use without there is life; and you have said nothing yet to show me that you know what life is, or how it is put into the egg. It seems to me that you have omitted the most important factor in the whole reckoning, and that your reckoning is entirely invalidated by the

omission."

Well," said the Doctor, with a smile, and not a very pleasant one, "I cannot, of course, expect to eradicate inveterate prejudice in one conversation. But think it over, and you will see that I am right. Never mind the egg; look at the exact mode of accounting for all your movements, on the principle of the equivalents of heat.

"How many equivalents go to a thought?" asked I.

"It is difficult to say exactly," replied he. "It depends on the

molecular changes in the brain. We know the principle is the same, because mental work exhausts the system, and requires food, like physical work. We cannot ascertain everything at once, but we are on the road to do so. There is no doubt as to the principle."

"Then," said I, "supposing thought to require so little fuel that we may leave that out of the question for the time, all animal motion, you say, is due to combustion of animal tissue?"

"Yes," said he, "that is indubitable."

"Then, if you could measure all the animal motion going on in the world in millions of horsepower, you would have a measure of the consumption of animal tissue?"

the combination of the elements into that tissue. That force is what I call life, and until you give me some better explanation, I shall take the liberty to call it a vital force, or a direct exertion of nonmaterial powers, which oldfashioned folk, like myself, call spiritual power."

"Oh," said he, rather testily, "if you get on that old tack again it is of no use talking."

"I beg pardon," said I; "I have tried to follow your tack exactly. You say that the demonstration of the non-existence of a soul, a Creator, or a spiritual existence, is derived from the fact that the liberation of heat by the combustion of animal tissue accounts for all animal motion. There may,

perhaps, be two words about that. But, allowing it to be the case, I put the question, what combines these elements ? They are not found combined. You cannot combine them. It is only by the vital process that they are combined. It follows that there is a non-material cause of the vital process, to which, in the first instance, all vegetable growth, and then all animal growth, and all animal motion, as well as all the resistance of organic matter to decay, are originally due. That something is what I mean by spirit or spiritual power."

"Positively," said the Doctor, "I shall miss the train if I don't run. Good day." And off he set at a round pace, leaving me by no means wholly convinced that he knew himself to be quite right.