hurriedly closed because of an empty war-chest. That is quite a different thing, however, from being afraid to go to war lest it should upset a world-wide money market counting its wealth by thousands of millions. Surely it would be easier to manipulate these thousands of millions so as to keep the financial world moving, than it was in Pitt's time to make bricks without straw and to fight on an empty Treasury. After all, a Bourse panic is not an unmitigated evil. It implies the existence of wealth, and the most demoralised kind of wealth must be better than none whatever.

'So far from Mr Norman Angell's theory of the restraining influence of a complex international banking system on militarism being true, the very opposite conclusion would be more plausible, and I believe also more correct. Very possibly our next big war will play havoc at the start, both with banks and bourses, but after the first shock the financial machinery might soon be readjusted. Then its vast ramifications, its innumerable devices for utilising credit, and its world-wide network of exchanges, far from being a hindrance to the operations of a war, would greatly facilitate them.'

It is a pity that Mr Lawson in all his 441 pages of diatribes against Mr Angell, Mr Lloyd George, Sir Edward Grey, the advocates of increased armaments and those who urge disarmament, does not tell us how this desirable result is to be achieved. The impression we are left with is that Mr Lawson has presented a good case very badly, while Mr Angell has argued a bad case very ably. It is high time that someone qualified to speak with authority on questions of international finance should investigate this aspect of modern war, and give to the world not only his conclusions but the process of reasoning by which he was led to form them. If he is able to do so without vilifying individuals, whether statesmen or writers, who disagree with him, his work will be the more valuable to his countrymen, because it will carry more weight.

From the New Pacificism of Mr Angell, with its insistence on the importance of material things, and Mr Lawson's inadequate reply, it is almost a relief to turn to the pages of Mr Grane's book, The Passing of War'; for here, in what we believe to be the swan-song of the older Pacificism, we do find at any rate adequate recognition of the fact that great wars are not waged for

purely material ends. The burden of Mr Grane's argument is that war is ethically wrong, and that no motive justifies the resort to force for the accomplishment of any national purpose. The argument is well presented and is supported by considerable erudition, but, since it is an argument with which the world has long been familiar, we need not dwell upon it now. It is not the Old Pacificism but the New which is making itself felt in the modern world as a solvent of nationality and as the foe of all patriotic ideals.

In conclusion, we would advise all Pacificists-both Old and New-to take to heart the advice of Prof. William James (p. 283), and

'enter more deeply into the æsthetical and ethical point of view of their opponents. . . . So long as anti-militarists propose no substitute for war's disciplinary function, no moral equivalent of war, analogous, as one might say, to the mechanical equivalent of heat, so long they fail to realise the full inwardness of the situation. . . . Our socialistic peace-advocates all believe absolutely in this world's values ; and instead of the fear of the Lord and the fear of the enemy, the only fear they reckon with is the fear of poverty if one be lazy. . . . The weakness of so much merely negative criticism is evident-pacificism makes no converts from the military party. The military party denies neither the bestiality, nor the horror, nor the expense; it only says that these things tell but half the story. It only says that war is worth them; that, taking human nature as a whole, its wars are its best protection against its weaker and more cowardly self, and that mankind cannot afford to adopt a peace-economy.'

Art. 11.-AIRSHIPS AND AEROPLANES.

1. The Aeronautical Classics. By T. O'B. Hubbard and J. H. Ledeboer. Published by the Aeronautical Society, London, 1911.

2. A Brief History of the Aeronautical Society. By A. E. Berriman. The Aeronautical Society, London, 1912. 3. Notre Flotte Aérienne. By W. de Fonvielle and G. Besançon. Paris: Gautier Villars, 1908.

4. Stability in Aviation. By G. H. Bryan, Sc.D. London: Macmillan, 1911.

5. Étude de la Stabilité de l'Aéroplane. By G. de Bothezat. Second edition. Paris: Dunod et Pinat, 1912.

6. Aerodynamics and Aerodonetics. By F. W. Lanchester. Two vols. London: Constable, 1912.

7. Résistance de l'Air et l'Aviation. By G. Eiffel. Paris: Dunod et Pinat, 1912.

8. Reports of the Advisory Committee for Aeronautics, 1909-10. London: Wyman, 1910.

9. Proceedings of the Institution of Automobile Engineers, 1911. London: Inst. of A. E., 1911.

In the evolution of an art such as flying one can often trace three distinct lines of progress-empirical, mathematical and practical-based respectively on phantasy, reason and experience. No start would have been made without the first, no progress without the second, no security gained without the third. Many experiments are made under the stimulus of a kind of instinct and more or less at random, usually by men whose minds are not trammelled by a scientific or engineering occupation. These give suggestions for more reasoned experiments, which, if successful, develope enthusiasts who either continue diving for a lucky solution till their fortunes are exhausted or made, or, if their disposition so guides them, follow the slower but more scientific indication of applied mathematics.

To-day in aeronautics a rational and scientific influence is beginning to make itself felt; the mathematical studies of the Advisory Aeronautical Committee, of Lanchester, of Bryan, of Crocco and of de Bothezat are very different from what they were a few years ago. Lanchester

was early and had occasion to complain that no one read him-save in Japan! But now the physicist is being urgently called upon to supply the premises on which to build laws, agreements, curves and approximations which the ordinary man would certainly call mathematical. Rigid dynamics and the mathematics of discontinuous fluids are an important branch, if not the essence, of studies in stability; hence the chief problem in aviation to-day is not very susceptible of treatment in non-technical form.

A round stone placed in calm water goes rapidly to the bottom, and a bubble released under water soon goes to the top; but a thin slate set flat under the surface will travel sideways with a comparatively slow downward trend. If the bubble be enclosed in a bladder and loaded, it can be made to stay in mid-water; and the slate, as can be surmised by any schoolboy who has made 'ducks and drakes,' can be kept up so long as its swift lateral motion is continued by a sufficient force.

No doubt the behaviour of the bubble and the slate, which recalls that of the balloon and aeroplane, was known to the ancients, who also knew the air to be a fluid. If they did not press the analogy and so float or fly, it is partly because they were not aware that the air has weight, and partly because their command of materials and, of course, of power was so restricted in comparison with ours. Even when they emptied a bottle by a vacuum pump or a siphon, they probably failed to measure the loss of weight due to the air removed. It was accordingly some time before the use of an empty sphere was suggested for flotation. We, on the other hand, know that a cubic yard of air weighs more than two pounds; and the proper conclusion from this is that a hollow sphere having no weight, but enclosing a vacuous space of one cubic yard, is subjected to an upward pull of over two pounds.

In 1670 the Jesuit Lana appreciated this, and suggested that a rigid shell emptied of air could float in air like a bubble in water, and that a man might be raised by such means. He also perceived a difficulty, viz., that to enclose for this purpose a number of shells, say of one cubic yard content, would require each shell to be so thin that it must weigh under two pounds if there was to be

any margin of lift-an impracticable degree of lightness. His mathematical training showed him how to evade this, though he never flew in fact. He showed the only way in which such a difficulty might be overcome, and at this early date gave the theorem which later emboldened Zeppelin and Lebaudy, the apostles of the enormous balloon, to work on such a vast scale. He saw that, when the volume of the ball is increased, not only is the 'lift' increased, but the amount of surface of the enclosing shell is not increased in proportion. Therefore, said he, without perhaps fully appreciating what other difficulties might be introduced by the stupendous dimensions which he was unwittingly contemplating, there must be some large dimension at which not only flotation, but flotation with a margin for lifting a man, can be secured. That the atmosphere would press in very heavily on the exhausted metal balloon, did not deter him, as he did not know how strong against collapse a metal balloon might have to be; and unhappily for him he did not know how to dispense with the vacuum by substituting for it in his balloon the light gas, hydrogen, or the light gas, hot air.

At the present day hydrogen is always used where the utmost lift is required; coal-gas, whose employment for balloons was introduced by Charles Green in 1820, is used where cheapness is of paramount importance. It is usual to say that 1000 cubic feet of hydrogen can lift 70 lb., and that 1000 cubic feet of coal-gas can lift 30 lb.; and, as the cost of hydrogen has within the last year or two been much reduced, it is possible to say that, for equal lift in districts where hydrogen is a by-product of alkali works, even price is not in favour of coal-gas.

So long as directed flight had not been achieved, flight itself was an object; but to-day the object of flight is to reach a particular place, the way of the air being preferred because other routes are impeded by terrestrial obstacles. It is true that the reaching of a desired point by balloon can often be effected on a day which may be too windy for any aeroplane to start; but the return cannot be made, and even reaching the goal depends upon searching the sky for an air-current which travels appropriately. This search is made by rising and falling to get clear of one current which is unfavourable and