534 



NA TURE 



[September 24, 190b 



University, and the amount will be increased eventually 

 to something like i6o,ooo2. ; and the same university has 

 also received from its class of '83 the sum of 20,oooi. 

 Princeton University has announced a gift of 50,000/. 

 from Mrs. Russell .Sage, and the University of Virginia 

 received the same amount by the will of 'the late Mr. 

 E. W. James. Mr. Andrew Carnegie has given 40,000/. 

 to the Mechanics Institute of New York City and 20,000/. 

 to Rochester University. The Hampden Agricultural 

 School obtained 32,000/. by the will of the late Miss Alice 

 Byington, and from that of the late Mr. Warren D. Potter 

 the Massachusetts College of Pharmacy has benefited to 

 the extent of 30,000/. The children of the late Rev. 

 Orlando Harriman have presented 20,000/. to Columbia 

 University, and Yale University has received 15,000/. by 

 the will of the late Mr. G. B. Griggs. There would not 

 appear to be any falling off in the enthusiasm shown for 

 higher education by wealthy Americans, who continue to 

 be fully alive to the need for well-endowed colleges 

 throughout the States in order to fit American citizens to 

 hold their own in the ever-increasing industrial competi- 

 tion. 



Lord Rosederv opened the new engineering laboratories 

 of the Heriot-Watt College, Edinburgh, on September 16, 

 and delivered an inspiring address, in which he reviewed 

 the history of the college and emphasised the value of 

 technical training. After reminding the audience that Sir 

 Walter Scott once said it was, in his opinion, as great 

 a crime to hide knowledge from the people as it would 

 be to hide the sun from them if we had the power, Lord 

 Rosebery pointed out that the Heriot-Watt College was 

 one of the first institutions founded in Great Britain for 

 the express purpose of giving evening instruction to 

 artisans, and it was the parent of all the mechanics' 

 institutes and polytechnics that now are so rife and so 

 much used throughout the country. It began by teach- 

 ing only the principles of mechanics and chemistry and 

 other branches of science of practical application to the 

 several trades in Edinburgh. Now it works with the 

 University, and gives what is practically extra-mural 

 teaching, and while training in the evening classes corre- 

 sponds to that given in the trade and commercial schools 

 m Germany, the day college is doing the work which is 

 done in the technical universities of Germany. Referring 

 to the work of the day students. Lord Rosebery had some- 

 thmg to say to employers of labour. If the number of 

 day students could be multiplied, and if it were found 

 possible for employers to give their apprentices days for 

 study, besides the evenings that apprentices furnish for 

 themselves, both the students and the employer would find 

 their reward. If the college is ever to receive its full 

 development, that fact will have to be recognised, and 

 the number of day students will have to be greatly 

 enlarged. Dealing with the training of specialists, the 

 suggestion was made that the technical institutes in our 

 great university towns should each specialise one side of 

 their teaching to the extent that it would not be necessary 

 to repeat it in other university towns, but that it could 

 be carried to the highest pitch' in each institute, and that 

 each institute, being recognised by other local universities 

 as regards the acceptance and reception of their students 

 in these special branches, there would be an enormous 

 advantage for the universities, and a vast economy of 

 teaching power. " What a magnificent and inspiring sight 

 IS the contemplation of these thousands of students who 

 utilise this college," said Lord Rosebery towards the end 

 of his address. " They come, not forced, to education, as 

 is the case in so many of our class of gentle birth, but 

 after a day's hard work, determined, whatever their stress 

 or fatigue may be. to utilise their evenings for the raising 

 of their minds and the perfecting of their methods. There 

 is no more encouraging symptom in any community than 

 this, and if we can even contemplate the possibility of a 

 nation in the main composed of such youths, the nation 

 will have nothing to fear in the long run. It is on its 

 honest and strenuous youth that every nation depends, 

 and youth such as that, determined and resolute on its 

 own perfection and its own efficiencv, is the surest sign 

 of the health and strength of a country." 



NO. 20,10, VOL. 78I 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, June 4, — "The El'*cirical Qualilies of 

 Porcelain, with Special Reference to Dielectric Losses." 

 By Dr. H. F. Haworth. Communicated by Prof. W. E. 

 Ayrton, F.R.S. 



This research was undertaken to determine some of 

 the electrical qualities of porcelain, and their variations 

 with respect to potential, temperature, and time. The 

 electrical properties investigated, and the results briefly 

 stated, are as follows : — 



A. Capacity Measurements. 



(i) The rate of charge of a porcelain condenser. 



The rate of charge is comparatively slow ; practically 

 the porcelain is fully charged in one minute, if we take 

 the first galvanometer swing as a measure of the capacity. 



(2) The charge of a porcelain condenser as a function 

 of the potential. 



For potentials up to 1200 volts the charge was directly • 

 proportional to the potential, if the potential changes were ' 

 made slow enough. 



(3) The influence of sudden cyclical changes of potential 

 on the charge of a porcelain condenser. 



If the potential changes were made rapidly the charge 

 was not quite proportional to the potential. .\ lagging 

 effect was shown, indicating a loss in the dielectric. 



(4) The dielectric constant, measured after one minute's 

 electrification, varied with the temperature according to 

 the following laws : — 



Between 0° and 30° C, Cr = Co f I -I-O'oo22 V + O'OOOj^-). 

 Between 30 and 100° C, C, ^C,.,.t»-'«"('i-'2). 



The dielectric constant at 20° C. was 8-95. 



B. Conductivity Measurements. 



(5) The apparent conductivity of porcelain, as measured 

 by the ratio of current to potential, varies with the applied 

 potential and the duration of the application. The 

 dielectric polarises, or generates a back E.M.F., when a 

 potential difference is applied to it. The conducting 

 mech.'mism shows viscosity. 



(6) The apparent conductivity of porcelain, measured 

 after one minute's electrification, increases with the 

 temperature according to the following law : — 



The specific conductivity at 20° C. is o-2624Xio-" 

 mhos per centimetre cube. 



C. Dielectric Loss Measurements. 



(7) The dielectric loss varies as the i-74th power of the 

 applied voltage, and is independent of the time of the 

 cycle. 



The dielectric losses at high potentials, and reason..''»le 

 frequencies, may be termed hysteretic (i.e. independent of 

 the time of the cycle of electrification). At very slow 

 frequencies the loss is mainly C^R loss, and this shows 

 viscosity effects ; but these losses are swamped at worl<ing 

 frequencies by the dielectric hysteresis. 



The dielectric loss was measured by the difference of 

 temperature which could be maintained by the central 

 surface of the porcelain plate above atmospheric tempera- 

 ture. This temperature difference being only a few 

 degrees, it follows from Newton's laws of cooling that 

 the heat lost is proportional to this difference, and as 

 the heat lost is equal to the heat gained, if the 

 temperature is constant, a thermopile placed with one 

 end in contact with the porcelain will generate an E.M.F. 

 which is directly proportional to the dielectric loss. This 

 E.M.F. was measured by connecting the thermopile to a 

 low-resistance galvanometer, and noting the direct and 

 reversed deflections to eliminate the effect of local 

 E.M.F. 's, &c. The losses were first measured at constant 

 frequency of fifty per second, with pressures up to 

 38,000 volts (R.JiI.S.), and were then determined at 

 constant pressure. 30,000 volts R.M.S., and for frequencies 

 between 15-8 and 200. 



