novel, and it is not fully evident that Miss Maude Radford Warren clearly perceives how vicious, dangerous, and mischievous a creature is Callahan, the Chicago boss, whom she introduces in "The Land of the Living"; but her description of his behavior is strictly true to nature. Having informally adopted and educated an orphan boy, and finding him honest to the core, he abstains from using his services in his own work, and allows a "reforming" Irish politician to train him in public affairs. Secretly, Callahan's heart is set upon his ward's marriage with an impoverished Irish gentlewoman whose estate he has bought, and when he finds the reformer in his way, he deliberately leads him into dishonesty, political and personal, and after he is corrupted beyond redemption, amiably presents him to the United States of America as a Senator. Not one of the personages in the tale seems to perceive that Callahan's behavior is in any point unbecoming an American citizen and to the Irish gentlewoman he "stands for loyalty and enduring love," not for treason to his adopted country. Miss Warren's merit is her perfect apprehension of an uneducated Irishman's ideal of friendship, a very noble and beautiful ideal. Had she noted that the man holding it must be wonderfully clear-sighted and strong-willed to distinguish and observe the dividing line between his personal privilege of selfsacrifice, and his political duty to preserve public interests inviolate her novel would have been illuminating to all readers; as it stands, it will gratify those who enjoy a true picture, even if the artist do not fully recognize its meaning. Harper & Brothers.

"To the memory of those gallant Americans, the officers of native troops, who fell during the Pulajan campaign in the Island of Samar, 1904-1905, and

of that brave and well-beloved Englishman, Amyas Portal Hyatt, who died towards the close of that campaign in Manila Hospital." Thus does Mr. Stanley Portal Hyatt dedicate his "The Little Brown Brother," a book written in defence of the white man's right to protect himself against violence while carrying civilization to the tropics, and in opposition to the theory that white, brown and black men are precisely similar, and therefore have the same desires, necessities, and capabilities. Opinion in regard to the value of such a book depends upon political belief, and some will find the story lamentably unkind to innocent brown folk, and others will see in it a just defence of the white man's character and conduct. All will agree that the picture of the fearless English girl and her father alone with the halfbreeds and savages of a Philippine Island, looking for defence to the American officers near them, is as interesting as any of those to be found in English fiction with the scene changed to India and all the white characters English. The hero is a good lover and a good fighter, and the plot abounds in intrigue and is well arranged. Naturally, the combatants on one side being savages and fanatics, there are many scenes of horror, but none going beyond the point of the despatches received by respectable papers, and the pictures of the peace-at-any-price civilian agree with those which he himself has outlined in his letters and books. The American soldier is praised in the most glowing terms, both in the preface and in the story, and the governor-general of 1904-1905 and the editor of the American newspaper are commended as highly as the soldiers. But as was said at first, the reader's opinion is settled by his preference for his own race or another. Henry Holt & Co.

The recent construction of machines on which, for the first time in history, men have flown through the air, coupled with the prospective growth of the dirigible balloon into an airship, has led to a widespread impression that aerial flight is soon to play an important part as an agency in commerce. Such a feeling is quite natural under the circumstances. In forecasting the possible results of invention we begin by reasoning from analogy, and the progress of invention in the direction of aerial navigation, with its alternations of success and failure, is at first sight very like what we have seen in the beginning of every new system of developing the powers of nature. Possibilities of great results have first been shown; then, step by step, difficulties have been overcome, until possibilities have grown into realities. The possibility of aerial flight has been shown both in theory and practice, and the difficulties now encountered in perfecting it seem quite like those met with in perfecting the steam engine, the telegraph, and the telephone. The present movement has an advantage over the preceding ones in that its ultimate outcome is more clearly in sight. We find it easier to imagine ourselves flying through the air in balloons or upon aeroplanes than it was a century ago to conceive of the world's commerce being carried on by the power of steam. We can best judge the possibility that this prospect will be realized by first considering what it has in common with the past, and then inquiring whether we have any grounds more secure than analogy on which to base a forecast.

It might seem that there can be no better ground for now limiting what may be hopefully expected from the "conquest of the air" than there was a

century ago for limiting what could be expected from the development of steam navigation. At each early stage, from the time when steam was applied to the propulsion of boats on the Seine and the Hudson, to the date when the first steamship crossed the Atlantic, it was easy, by taking what was known as the measure of the future, to show that no great result could be expected from the new system. With the earlier engines no ship could cross the ocean. But improvement in engines was brought about both by invention and by the development and application of physical principles. The theory of the steam engine, and indeed of heat engines in general, had been set forth by Carnot, but the ideal steam engine to which this theory led was so far outside the practical reach of the time that the earlier inventors and engineers paid little attention to it. Only the germ of the theory of energy had been found by Rumford, and it was not until it had been farther developed that it could be fully utilized in guiding invention. Thus it came about that, instead of the ocean steamship being rapidly developed, a century elapsed before it had assumed its present proportions. Is it not reasonable to expect that the airship, whether balloon or flyer, will have a similar history? This question cannot be answered by pointing out present imperfections. We all know that as a means of transportation it is, up to the present time, so expensive and so doubtful that it is only from future improvements that any important result can be expected. We must inquire whether there is any well-defined limit to future improvement, and, if there is, learn where we shall stand when, if ever, that limit is approached.

One word as to the trend of our in

quiry. The vital question is not whether aerial navigation is practicable, for that has been settled in the affirmative. In the time of Montgolfier it was shown that men could rise and float in balloons; twenty years ago it was found that a balloon could be guided; now it is proved in the best of all ways, that of actual trial, that a man can fly through the air on an aeroplane. But we are all looking for more than the bare fact of sailing or flying above the earth. We wish aerial flight to serve some practical purpose in the world's work, and to compete with the steamship, the railway, or the mail-coach in the carriage of passengers or mails. The inquiry into which the reader is now invited to enter is, What measure of rational hope we can entertain of this consummation.

All the questions involved are, at bottom, those of physics and mathematics. The pivotal points are such as numbers of feet and pounds, the density of air, the tenacity of materials used in construction, and the resistance to motion under varied conditions. These can be discussed in the most satisfactory way only by mathematical computations. But it is not necessary to go into numerical details to find a basis for our conclusions. General principles, easily within the comprehension of every educated person, will serve our purpose as well as the most rigorous mathematical investigation.

I.

We must distinguish at the outset of our inquiry between advance in knowledge and progress in invention. No definite limit can be set to the possible future of knowledge, nor to results which may yet be reached by its advance. The best recent example of a discovery in the required line, indeed, the only example which suggests the possibility of extending the efficiency of a heat machine beyond the limit

now set by the theories of physics, is the finding in radium of a substance which emits energy in seeming defiance of the laws of energy. Ideally, the power of annulling the gravity of matter would perhaps be the most revolutionary one that we can think of. But the most refined experiments made with a view to discover whether anything can be reached in this direction have shown that by no method yet known can the gravitation of matter be altered in the slightest degree. Should some way of controlling or reversing gravitation be discovered; should it be found possible to make the ether react upon matter; should radium hereafter be produced by the ton, instead of by the milligramme; should some metallic alloy be found having ten times the tenacity and rigidity of steel-all our forecasts relating to future possibilities in the application of power would have to be revised.

But we must note that the present efforts of inventors are not taking this direction. They are accepting physical principles and the facts of engineering as they now stand, and are not seeking to discover new sources of radium, to find new alloys, or to bring out laws of nature hitherto unknown. Our forecast must therefore be based upon the present state of science, and can relate only to what is possible through invention being continued on lines it is now following. I enter this caveat not because there is any great probability of an epoch-making discovery in any of the directions just mentioned, but to define clearly the ground for our conclusions.

When we study progress in the application of power from this point of view, we see that it has, during the entire nineteenth century, been approaching fairly well-defined limits, which can never be extended except by some revolutionary discovery that has not yet cast even its shadow be