chamber in the same experiment. The pressures, moreover, are often greatly above those which would exist were the charge absolutely confined in a close vessel. A very striking instance may be cited from the early experiments of the Explosive Committee with a M.L. 10-inch gun (fig. 8). The first round was fired with a charge of 87 lb. Belgian Pebble, the charge being lighted in two places. The maximum pressure with the chronoscope was 25.2 tons. With the crusher gauge the pressure in the chamber varied from 22.2 to 24-8 tons per square inch, while the energy developed by the powder on the shot was 6,240 foot-tons. With the second round, all conditions being the same except that the charge was fired at a single point, the chronoscope pressure was as nearly as possible the same; but the chamber pressure was, at the rear, 79-1 tons; in the middle 52.0 tons; at the seat of the shot 39.5 and 48.0 tons per square inch. A similar large excess of pressure was shown at points 1 foot and 2 feet in advance of the seat of the shot, and the crusher gauges did not show their normal pressures until points 5 or 6 feet from the seat of the shot had been reached. Yet with the violent difference in pressure shown between the crusher gauges in this round and in the previous round (which I have just cited), FIG. S.-Position of Pressure Plugs in 10-inch Gun. the difference of energy developed in the shot was exceedingly trifling, being only 6,249 foot-tons, as against 6,240. I believe I have expressed pretty clearly my views that crusher gauges placed in the chase are for absolute determination not of much value, and their main use, if used at all, is to give comparative results. But the same remark does not apply to crusher gauges placed in the chamber. Gases moving at a high velocity in the chase are, so to speak, performing their proper function; but the same is not true of those violent waves of pressure in the chamber which appear to accompany the explosion of all brisante powders, and which occur either when the projectile has hardly moved at all or when it is moving with a comparatively slow velocity. It is our object, and in this we have had great success, to avoid these waves as much as possible; and in attaining this end our indebtedness to the crusher gauge is very great, as this instrument has made plain to us not only the extreme violence but the variability of these oscillations. I have heard it urged that these waves of pressure are, after all, not of high importance, because their maxima act at the same time only upon a very small section of the bore, and the continuity of the metal is amply sufficient to resist the stress. This is no doubt true, but it is not true of the base of the bore, which in modern guns is almost invariably a movable piece, and which under certain circumstances might have to sustain the full force of the violent pressures, a sample of which I have cited. To ascertain the mean pressure throughout the bore it seems to me that there is no method so satisfactory, despite its attendant labour, as that of making the projectile write its own story. In that case we cannot fall into the error of making the pressures three or four times as great as are necessary to generate the energy the projectile has actually acquired, while occasional errors, due to causes I have not time to explain, are easily detected and eliminated. To give an idea of how great is the range of velocity over which these experiments have been carried, I exhibit here diagrams (figs. 9 and 10) showing the velocities and pressures obtained with several of the new explosives which in recent years have attracted so much attention. Observe also how closely, with the exception of the one somewhat brisante powder, the results given by the chronoscope accord with those given by the crusher gauge. Where these differ, as I have elsewhere pointed out, the two modes of research so widely different are complementary to each other. The chronoscope takes little or no note of the violent oscillations of pressure acting during exceedingly minute intervals of time. On the other hand, if with the explosives I allude to we trusted to the indications of the crusher gauge, we should arrive at a most erroneous idea of the energy communicated to the projectile. In concluding, if I may venture to quote the excuse of a much more eminent man than myself, I have only to express my regret that I have not had time to condense the remarks with which I fear I have fatigued you, while at the same time I am aware that there are many important points in connection with my subject which I have left altogether untouched, and others upon which I have touched that require further elucidation. TRANSACTIONS OF THE SECTIONS. SECTION A.-MATHEMATICAL AND PHYSICAL SCIENCE. PRESIDENT OF THE SECTION-Professor A. W. RÜCKER, M.A., F.R.S. THURSDAY, AUGUST 9. The President delivered the following Address : It is impossible for a body of English scientific men to meet in one of our ancient university towns without contrasting the old ideal of the pursuit of learning for its own sake with the modern conception of the organisation of science as part of a pushing business concern. We are, as a nation, convinced that education is essential to national success. Our modern universities are within earshot of the whirr of the cotton-mill or the roar of Piccadilly. Oxford and Cambridge themselves are not content to be centres of attraction to which scholars gravitate. They have devised schemes by which their influence is directly exerted on every market town and almost on every village in the country. University extension is but a part of the extraordinary multiplication of the machinery of education which is going on all around us. The British Association, which was once regarded as bringing light into dark places, is now welcomed in every large provincial town by a group of well-known men of science; and we find ready for the meetings of our Sections, not only the chapels and concert-rooms which have so often and so kindly been placed at our disposal, but all the appliances of well-designed lecture-rooms and laboratories. I do not propose, however, to detain you this morning with a discourse on the spread of scientific education, but you will forgive me if I illustrate its progress by two facts, not perhaps the most striking which could be selected, but especially appropriate to our place of meeting. It is little more than thirty years since the two branches of science with which our Section deals, Mathematics and Physics, have been generally recognised as wide enough to require more than one teacher to cope with them in an educational institution of high pretensions and achievement. In 1860 the authorities of the Owens College, Manchester, debated whether it was desirable to create a Professorship of Natural Philosophy in addition to, and independent of, the Chair of Mathematics. It was thought necessary to obtain external support for the opinions of those who advocated this step. An appeal was made to Professors De Morgan and Stokes. The former reported that a course of experimental physics is in itself desirable;' the latter, that there would be work enough in a large institution for a mathematician and a physicist.' In the end the Chair of Natural Philosophy was established, and the fact that our host of to-day, Professor Clifton, was its first occupant reminds us how little we have advanced in time and how far in educational development from the days |