instead of 18,000—and although in every beat there are three processes, the whole follow so smoothly that the progression of the hand is practically continuous.

5. On a Direct Reading Form of Platinum Thermometer.
By G. M. CLARK, B.A.

The author described the pyrometer of Callendar and Griffiths. In this instrument the leads to the platinum coil are so arranged that only a single observation is necessary to determine its resistance. Further, by constructing the galvanometer so that its deflections are independent of the E.M.F. of the battery, the same increase of resistance of the coil will always give the same deflection on the scale. A wide range of temperature as well as an open scale is secured by the galvanometer being brought back to zero every hundred degrees. It is also pointed out that the fixed points' of these thermometers are not liable to variation.

As reliable experiments with the air thermometer above 700° C. have not yet been carried out, the author suggested the adoption of a platinum thermometer with fixed coefficients as a standard.

TUESDAY, AUGUST 14.

The following Report and Papers were read:

1. The Report of the Committee on Dryness of Steam.-See Reports, p. 392.

2. On the Temperature Entropy Diagrams.

By H. F. W. BURSTALL, M.A., A.M.Inst.C.E.

The treatment adopted in this paper has been to consider the temperature entropy diagrams, from the engineer's point of view, and as far as possible graphical methods are alone employed.

The reason of the great value of the diagrams lies in the fact that an area represents the heat required to effect the change denoted by the contour of the area; and when the actual expansion of the steam is plotted on the heat diagram it is easy to see by inspection where the losses of heat have occurred.

The ordinates of the curves are the absolute temperature and the entropy or heat weight.

The curves denoting the heat required to form a given mixture of steam and water can be drawn once for all; after that very simple arithmetic is all that is required to trace the expansion curve for any engine on the heat diagram.

The changes in the pressure and dryness of steam confined in a constant volume are shown by means of a model in space, in which the vertical distances represent the volume of steam, and the horizontal plane a temperature entropy diagram. On cutting the surface formed by a plane parallel to the horizontal plane we have a curve which gives the constant volume curves, and the construction follows at once from the model.

The paper was illustrated by diagrams from several types of steam engines, both compound and triple expansion, and the diagram for a gas engine was also shown.

3. On the Hunting of Governed Engines.1

By JAMES SWINBURNE, M.Inst.C.E.

Governors are generally considered as complete mechanisms without reference to the engines governed. Hunting, however, depends, not only on the governor, Published in full in Engineering, August 17, 1894.

but also on the inertia of the fly-wheel and the load on the engine. A Watt governor acting directly on the throttle or expansion valve does not hunt if designed for stability, but does not give the same speed at heavy as at light loads. If made isochronous it has either a dash-pot or a relay. In either case the action of the governor is not instantaneous, and a time-lag is introduced. This causes hunting, especially if the load is light and the fly-wheel heavy or fast-running. If the isochronous governor works a slow-acting relay the hunting may be so serious that the steam supply alternates between complete cut-off and full supply. The remedy is to use either an isochronous governor with no relay, so that the engine gets either full steam or none, or to use a stable governor acting direct with a supplementary relay gear to secure the same speed at full and light loads. The first method is not employed in large slow-running engines, as the fly-wheel would have to be enormous. The second is utilised in the Knowles supplementary governor, but a second governor is unnecessary, as one can fill both functions.

4. On Engineering Laboratory Instruments and their Calibration. By DAVID S. CAPPER, M.A., Professor of Mechanical Engineering, King's College, London.

The reliance to be placed upon observations made with measuring instruments evidently depends primarily upon the accuracy with which those instruments record. Neglect of this fundamental truth often leads to inaccurate and erroneous deductions from experiments which are themselves of the highest scientific value; not infrequently the whole value of observations may be destroyed by insufficient care in the calibration of the instruments used. The subject is therefore one of some importance. The author describes the chief sources of error in some of the most common engineering investigations, and their probable value, and points out some of the possible methods of correction where such exist. For example, in engine trials there are many possible sources of error. Most of these may be reduced in percentage value by continuing the trial for a sufficient period. But this is not the case with errors which may occur in the indicators, gauges, or spring balances used in the determination of power. In these, unless properly calibrated before trial, very serious errors may be introduced, amounting in some cases to 5 and 6 per cent. of the total power indicated. It is therefore absurd, even if proper precautions have been taken, to rely upon horse-power measurements to two places of

decimals.

Similarly with regard to tension and compression experiments with standard 10-inch bars. Here calibration of the testing machine is extremely difficult, and can in general only be carried out over a small portion of the range of the experiments. Deductions have therefore to be made from the less to the greater, with the result that small errors in the calibration will tend to be magnified. Vertical testing machines have fewer sources of error, and can be calibrated with more certainty, than horizontal machines. Extensometers are, however, much more easily applied to a horizontal bar than a vertical, and variable jockey weights, which are requisite if the same accuracy is to be maintained at low loads as at high, are also more readily adapted to horizontal machines.

Extensometers can be made and calibrated well up to the accuracy of the testing machine. With standard bars and a measuring instrument true to the tenthousandth of an inch, the modulus can be relied upon to the second significant figure. It is doubtful if more can be obtained without very special construction and calibration of the testing machine.

The difficulty in bending experiments, again, lies in the accurate application of load. Unless the beams are very short or of unmanageable cross-sections, the load measurement must be very delicate if readings approaching the accuracy of those in tension are to be obtained. It is possible that some of the discrepancies in published beam experiments may be due to this cause.

The paper deals shortly with other cases where calibration is specially needed, to which the limits of this abstract do not permit a more extensive allusion.

5. On Lighthouse Apparatus and Lighthouse Administration in 1894. By J. KENWARD, F.S.A., Lighthouse Engineer.

The writer referred to the principles that govern the establishment of modern lights, and described the chief forms of apparatus now best available for the optical engineer, e.g., the single flashing or the group-flashing holophotal revolving; the fixed and occulting; the lenticular revolving, having refracting centres alone, extended to high vertical angles; and the quick-flashing lights of recent French types called feux-éclairs.

He compared the dimensions or orders' of various apparatus, and the radiants of gas, oil, and electricity, and discussed the question of fog in relation to these. He called attention to the need of good ship-lights on the dioptric system, having equality of power in the beam.

He suggested certain reforms in lighthouse administration and in lighthouse statistics.

6. On Spring Spokes for Bicycles. By Professor J. D. EVERETT, F.R.S.

The author described a construction of spring-spoked wheels for bicycles in which both lateral and rotational yielding are so moderate in amount as to occasion no inconvenience. Each spoke consists essentially of a small coil spring, weighing half an ounce, attached to a light spoke wire, the connections of the ends of the spoke to hub and rim, as well as the connection between spring and wire, being of the hook-and-eye kind. The attachment to the rim is made, not at the centre of the rim, but at its edges, semicircular notches being cut, into which the spokes are hooked, and the spokes attached to either edge of the rim are attached to the opposite flange of the hub, so as to cross the plane of the wheel. The spokes of the driving-wheel are not exactly radial, but slope a little backwards and forwards alternately-an arrangement which materially diminishes rotational yielding, while the crossing above described diminishes lateral yielding.

It has generally been maintained that, while up-and-down elasticity is useful for relieving jolts, lateral and rotational yielding are evils to be avoided. The author differs from this view, and maintains that both lateral and rotational yielding, of the elastic kind, when kept within proper limits of magnitude, are beneficial both as regards comfort and speed.

When one of the wheels of a bicycle encounters an obstacle (such as rough roads abound with), the collision produces an impulsive reaction on the wheel, as if the obstacle struck the wheel. Sometimes the direction of the blow lies in the plane of the wheel, but in many cases the wheel is not only checked and lifted, but at the same time driven to one side. In order to cushion the lateral component of the blow there must be lateral yielding. Accordingly, in running over patches of stones, which jerk the ground-point of a wheel from side to side, the usual jarring of the hands and disturbance of the steering are noticeably absent in bicycles with spring spokes.

As regards a blow delivered in the plane of the wheel, the impulse may be resolved into a radial and a tangential component. The radial component is cushioned by the shortening of the spokes in the neighbourhood of the point of impact, and the lengthening of the diametrically opposite spokes.

The tangential component is equivalent to an equal and parallel impulse on the rim in a line passing through the centre, combined with a torque. The torque, from the symmetry of its action round the axle of the wheel, produces no jar; but the impulse in a line through the centre tends to drive the rim backwards and slightly downwards, with respect to the axle. It is cushioned by the elastic shortening and lengthening of spokes which are nearly horizontal.

The elastic yielding of a pneumatic tyre is mainly in the radial direction, and is practically nil in the tangential direction. Its lateral yielding is very much less than that afforded by spring spokes.

Next, as regards rotational yielding of the driving-wheel, the propelling force

applied by the rider to the pedals is given out at the ground-point of the wheel in the shape of back-pressure of the wheel against the ground. The more rigid and unyielding the connection between these two parts of the mechanism is, the greater will be the tendency to jarring of the feet by inequalities of the ground. Even on smooth ground there is a jerk at the beginning of each stroke, in the case of an unyielding wheel, which tends to fatigue the knee. The difference between the energy given to the springs and the energy which they return is quite trifling in comparison with the saving of energy which results from the easing-off of concussions. Moreover, the energy stored in the springs is useful in carrying the wheel past the dead-points, a small pressure unconsciously exerted on the pedals being sufficient to retain the energy till it is wanted.

An indirect benefit from lateral yielding is the diminution of side-slip. Sideslip will begin as soon as the lateral force called out between the wheel and the road at the ground-point exceeds a certain limiting amount. Lateral yielding eases off the suddenness of lateral impulses, thus keeping down the maximum amount of lateral force; and this is precisely what is required for preventing side-slip.

In some of the driving-wheels which the author has constructed the hub is allowed to project much farther on the side remote from the driving-chain than on the side next the chain, in order to permit the combination of a wide hub with a narrow width between the pedals. Weaker springs are used on the projecting side than on the other side. This unsymmetrical arrangement is not found to interfere with the ease of steering.

SECTION H.-ANTHROPOLOGY.

PRESIDENT OF THE SECTION-Sir W. H. FLOWER, K.C.B., LL.D., Sc.D., F.R.S.

THURSDAY, AUGUST 9.

The President delivered the following Address:

It is not usual for the President of a Section of this Association to think it necessary to give any explanation of the nature of the subjects brought under its cognisance, or to emphasise their importance among other branches of study; but so general is the ignorance, or at all events vagueness of information, among otherwise wellinstructed persons, that I will ask your permission to devote the short time accorded to me before the actual work of the Section begins to giving some account of the history and present position of the study of Anthropology in this country, and especially to indicate what this Association has done in the past, and is still doing, to promote it.

It is only ten years since the Section in which we are now taking part acquired a definite and assured position in the organisation of the Association. The subject, of course, existed long before that time, and was also recognised by the Association, though with singular vicissitudes of fortune and position. It first appeared officially in 1846, when the Ethnological sub-Section of Section D' (then called 'Zoology and Botany') was constituted. This lasted till 1851, when Geography parted company from Geology, with which it had been previously associated in Section C, and became Section E, under the title of Geography and Ethnology.' In 1866 Section D changed its name to 'Biology,' with Physiology and Anthropology (the first occurrence of this word in our official proceedings) as separate Departments;' but the latter does not seem to have regained its definite footing as a branch of Biological Science until three years later (1869), when Section E, dropping Ethnology from its title, henceforward became Geography alone. The Department for the first two years (1869 and 1870) was conducted under the title of Ethnology, but in 1871 it resumed the name of Anthropology, given it in 1866, and it flourished to such an extent, attracting so many papers and such large audiences, that it was finally constituted into a distinct Section, to which the letter H was assigned, and which had its first session at the memorable meeting at Montreal, exactly ten years ago, under the fitting and auspicious presidency of Dr. E. B. Tylor.

The history of the gradual recognition of Anthropology as a distinct subject by this Association is an epitome of the history of its gradual growth, and the gradual recognition of its position among other sciences in the world at large, a process still in operation and still far from complete. Although the word Anthropology had certainly existed, but used in a different sense, it was not till well into the middle of the present century that it, or any other word, had been thought of to designate collectively the scattered fragments of various kinds of knowledge bearing upon the natural history of man, which were beginning to be collected from so many diverse sources. Indeed, as I have once before upon a similar occasion remarked, one of the great difficulties with regard to making