REPORTS

ON THE

STATE OF SCIENCE.

Report of the Committee, consisting of Professor Sir WILLIAM THOMSON, Professor CLERK MAXWELL, Professor TAIT, Dr. C. W. SIEMENS, Mr. F. J. BRAMWELL, and Mr. J. T. BOTTOMLEY, for commencing Secular Experiments upon the Elasticity of Wires. Drawn up by J. T. BOTTOMLEY.

Ar the last meeting of the British Association, the arrangements for suspending wires for secular experiments in the tube which has been erected in the tower of the Glasgow University Buildings, and for observing these wires, were described and reported as complete. Some improvements have since been found necessary; but, so far as these are concerned, there is not much to add to the report then given.

The long iron tube has been closed at the top and bottom so as to keep out currents of air and dust, and the joints of the tube have been carefully caulked.

Some improvements in the cathetometer used for observing the marks on the wires were also found to be required, but the instrument is now satisfactory.

Six wires have now been suspended in the tube; their stretching weights have been attached to them, and they have been carefully marked and measured. These wires are suspended in pairs-two of gold, two of platinum, and two of palladium. One of each of the pairs is loaded with a weight equal to one-twentieth of its breaking weight, and the other of each pair with a weight equal to one-half of its breaking weight. The points of suspension for each pair are very close together, so that any yielding of the place of support affects both wires equally.

Each wire is marked with paint marks, and there are other marks on the wires and on the weights attached to them where positions have been determined. These marks are described in a laboratory book which is at present kept in the room of the Professor of Natural Philosophy in the University of Glasgow. The measurements that have been made, and the experiments that have been undertaken in connection with the work assigned to the Committee, are all being entered in this book. This, 1879.

D

however, can only be regarded as a temporary mode of keeping these records.

It is intended that the record in this book shall contain

1. Description of the tube and arrangements for suspending the wires, and for suspending additional wires at future times, and description of the mode of attachment of the stretching weights.

2. Description of the cathetometer and method of measuring the changes, should there be any, in the lengths of the wires.

3. Description of the wires themselves, and record of experiments that have already been made on them as to breaking weight and Young's Modulus of Elasticity.

4. Description of the marks put on the wires, and record of the measurements that have been made as to the lengths of the wires and as to the relative positions of the marks at the time of suspending the wires.

The stretching weights and the clamps attached to the wires are engraved each with the amount of its weight in grammes. The measurements are all made in grammes and centimetres.

It seems desirable, considering the nature of the experiments that are just now commencing, that information regarding them should be preserved to the British Association in some appropriate way; and that provision should be made for recording every change that may take place, and for communicating from time to time to the Association such information as may be obtained.

In the report presented to the Association by this Committee last year, it was mentioned that experiments had been commenced in the laboratory of the University of Glasgow in connection with the present investigation on the effects of stress maintained for a considerable time in altering the elastic properties of various wires. These experiments are still being carried on, and results of interest and importance have been already arrived at.

It is

The most important of these experiments form a series that have been made on the elastic properties of very soft iron wire. The wire used was drawn for the purpose, and is extremely soft and very uniform. about No. 20 B.W.G., and its breaking weight, tested in the ordinary way, is about 45 lbs. This wire has been hung up in lengths of about 20 feet, and broken by weights applied, the breaking being performed more or less slowly.

In the first place, some experiments have been tried as to the smallest weight which, applied very cautiously and with precautions against letting the weight run down with sensible velocity, will break the wire. These experiments have not yet been very satisfactorily carried out, but it is intended to complete them.

The other experiments have been carried out in the following way:It was found that a weight of 28 lbs. does not give permanent elongation to the wire taken as it was supplied by the wire-drawer. Each length of the wire, therefore, as soon as it was hung up for experiment, was weighted with 28 lbs., and this weight was left hanging on the wire for 24 hours. Weights were then added till the wire broke, measurements as to elongation being taken at the same time. A large number of wires were broken with equal additions of weight, a pound at a time, at intervals of from three to five minutes-care being taken in all cases, however, not to add fresh weight if the wire could be seen to be running down under the effect of the weight last added. Some were broken with weights added at

the rate of one pound per day, some with three quarters of a pound per day, and some with half a pound per day. One experiment was com menced in which it was intended to break the wire at a very much slower rate than any of these. It was carried on for some months, but the wire unfortunately rusted, and broke at a place which was seen to be very much eaten away by rust, and with a very low breaking weight. A fresh wire has been suspended, and is now being tested. It has been painted with oil, and has now been under experiment for several months.

The following tables will show the general results of these experiments. It will be seen, in the first place, that the prolonged application of stress has a very remarkable effect in increasing the strength of soft iron wire. Comparing the breaking weights for the wire quickly broken with those for the same wire slowly broken, it will be seen that in the latter case the strength of the wire is from two to ten per cent. higher than in the former, and is on the average about five or six per cent. higher. The result as to elongation is even more remarkable, and was certainly more unexpected. It will seen from the tables that, in the case of the wire quickly drawn out, the elongation is on the average more than three times as great as in the case of the wire drawn out slowly. There are two wires for which the breaking weights and elongations are given in the tables, both of them 'bright' wires, which showed this difference very remarkably. They broke without showing any special peculiarity as to breaking weight, and without known difference as to treatment, except in the time during which the application of the breaking weight was made. One of them broke with 444 lbs., the experiment lasting one hour and a-half; the other with 47 lbs., the time occupied in applying the weight being thirty-nine days. The former was drawn out by 28.5 per cent. on its original length, the latter by only 4.79 per

cent.

Tables showing the Breaking of Soft Iron Wires1 at Different Speeds.

The wire used was all of the same quality and gauge, but the 'dark' and 'bright' wire bad gone through slightly different processes for the purpose of annealing.

It is found during the breaking of these wires that the wire becomes alternately more yielding and less yielding to stress applied. Thus, from weights applied gradually between 28 lbs. and 31 or 32 lbs., there is very little yielding and very little elongation of the wire. For equal additions of weight between 33 lbs. and about 37 lbs. the elongation is very great. After 37 lbs. have been put on, the wire seems to get stiff again, till a weight of about 40 lbs. has been applied. Then there is rapid running down till 45 lbs. has been reached. The wire then becomes stiff again, and often remains so till it breaks.

It is evident that this subject requires careful investigation.

Fourth Report of the Committee, consisting of Dr. JOULE, Professor Sir WILLIAM THOMSON, Professor TAIT, Professor BALFOUR STEWART, and Professor J. CLERK MAXWELL, appointed for the purpose of effecting the Determination of the Mechanical Equivalent of Heat.

THERE is little to be reported by the Committee this year, the work at present in progress being the protracted one for supplying the means of correcting errors in the determination of temperature arising from temporary changes of the fixed points of thermometers constructed of glass. The Committee have learned with pleasure that an extensive series of experiments has recently been made by Professor Henry A. Rowland, of Baltimore, who, being unaware of what had been done by the Committee, has arrived at an equivalent almost identical with that determined by Dr. Joule.

Report of the Committee appointed for the purpose of endeavour ing to procure Reports on the Progress of the Chief Branches of Mathematics and Physics; the Committee consisting of Professor G. CAREY FOSTER (Secretary), Professor W. G. ADAMS, Professor R. B. CLIFTON, Professor CAYLEY, Professor J. D. EVERETT, Professor CLERK MAXWELL, Lord RAYLEIGH, Professor G. G. STOKES, Professor BALFOUR STEWART, Mr. SPOTTISWOODE, and Professor P. G. TAIT. OWING to unforeseen circumstances only one meeting of this Committee has taken place during the past year. It seems desirable, nevertheless, in order that the question of the reappointment of the Committee may be fully considered, and that there may be a full expression of opinions on the subject referred to it, that a statement should be made to the Section of the proceedings of the Committee, the more so since, in the hope that greater progress would have been made by this time, no report was presented at the last meeting of the Association.

The first matter discussed by the Committee was the character and general plan of the reports which they should endeavour to procure; the next was to what extent or in what manner the production of such reports could be aided by the Committee. Important contributions to the discussion of these questions are contained in written communications to the Committee from two of its members-Professors Clerk Maxwell and Stokes. Professor Clerk Maxwell writes as follows:

'Reports on special branches of science may be of several different types, corresponding to every stage of organisation, from the catalogue up to the treatise.

When a person is engaged in scientific research, it is desirable that he should be able to ascertain, with as little labour as possible, what has been written on the subject and who are the best authorities. The ordinary method is to get hold of the most recent German paper on the subject, to look up the references there given, and by following up the trail of each to find out who are the most influential authors on the subject. German papers have the most complete references because the machinery for docketing and arranging scientific papers is more developed in Germany than elsewhere.

The "Fortschritte der Physik" gave an annual list of all papers, good and bad, arranged in subjects, with abstracts of the more important -ones. Wiedemann's "Beiblätter is a more select assortment, given more in full.

'I think it doubtful whether a publication of this kind, if undertaken by the British Association, would succeed. Lists of the titles of the proceedings of Societies and of the contents of periodicals are given in "Nature." These are useful for strictly contemporary science, and I do not think that a more elaborate system of collection could be kept up for long.

The intending publisher of a discovery has to examine the whole mass of science to see whether he has been anticipated, but the student wishes to read only what is worth reading. What he requires is the names of the best authors. The selection or election of these is constantly done by skimming individual authors, who indicate by the names they quote the men whose opinions have had most influence. But a report on the