454 



NA TURE 



[March 9, 1905 



responsible for their educational systems. The article pro- 

 ceeds to direct attention to the Thomason Civil Engineering 

 College at Rurki in connection with a proposal at a recent 

 meeting of the Allahabad University to abolish the faculty 

 of engineering, and favours the introduction in the college 

 at Rurki of the method of government which has assured 

 the success of the colleges of the City and Guilds. 



The Berlin correspondent of the Times states that in the 

 course of a debate on the estimates for the Ministry of 

 Education in the Prussian Chamber on March 2, an official 

 of that Ministry, Geheimrath Reinhardt, gave some interest- 

 ing information with regard to the success of the so-called 

 "reform schools." in which the study of the classics is 

 begun at the age of twelve, and Greek not until the age of 

 fourteen. One great advantage of this system is that the 

 decision to assign a pupil to the modern (Realschule) or to 

 the classical school (Gymnasium) can be postponed to a 

 stage when his abilities and tastes can be better estimated. 

 Geheimrath Reinhardt stated that the system of this " reform 

 school " had hitherto been adopted at thre» classical Gym- 

 nasia, and the result was that of 123 pupils in the highest 

 form who presented themselves for the leaving examination 

 only four failed to pass, and of these four three succeeded 

 six months later. Experience had shown that as a result 

 of beginning Latin and Greek at a later age than was 

 customary, the interest of the pupils in their work was ren- 

 dered keener, and their dfligence was certainly in no wise 

 inferior to that of the pupils of the ordinary Gymnasia. 



The fourth annual report of the executive committee of 

 the Carnegie Trust states that sums amounting to 38,11^;. 

 have been claimed and handed over to the four Scottish 

 universities during the year. The grants for library purposes 

 and for provisional assistance in teaching, ainounting in all 

 to 6400/., have been fully paid. The grants for buildings 

 and permanent equipment available for 1904, including a 

 balance of 12,635/. unexpended in 1903, amount to 33,035/. 

 Of these, the sum of 20,146/. has been claimed. Claims for 

 grants towards teaching endowments amount for the year 

 to 11,568/. These include contributions to the foundation 

 of two chairs — that of history in the University of Aberdeen, 

 and that of geology in the University of Glasgow. The 

 scheme of endowment of post-graduate study and research 

 has now entered upon its second year. The total expenditure 

 for 1903—4 under the scheme was 33S6/. The estimated 

 outlay for the current academic year is 5177/- Applications 

 for fellowships, scholarships, and grants for 1905-6 must 

 be lodged on or before May i with the secretary to the 

 trust, from whom application forms and regulations can 

 be obtained. In the research laboratory of the Royal College 

 of Physicians, the purchase of which was announced in the 

 previous annual report, the superintendent reports that the 

 past year has been one of steady and satisfactory work in 

 all departments. Thirty-five workers have held places in 

 the laboratory, and have been engaged in forty-seven in- 

 vestigations. 



The twenty-seventh annual general meeting of the In- 

 stitute of Chemistry was held on March i. In the course 

 of an address Mr. David Howard, the president, referred to 

 the steady growth of the institute, saying that he thought 

 there was still a wide field for those possessing the highest 

 cheinical knowledge and skill, and that those who had to 

 call in the aid of such knowledge and skill were becoming 

 more and more alive to the importance of employing only 

 the properly trained and coinpetent. He emphasised the 

 importance of requiring all candidates to produce evidence 

 of a high standard of general education. The professional 

 chemist should be a professional man as well as a chemist, 

 and must, therefore, possess that general culture which is 

 essential if he is to deal with his work in a professional 

 spirit. Referring to the position of the institute in con- 

 nection with the Sale of Food and Drugs Acts, he mentioned 

 that 94 per cent, of the public analytical appointments were 

 held bv fellows of the institute. The president alluded to 

 the action of the Board of .Agriculture in encouraging pro- 

 vincial technical and agricultural colleges to undertake pro- 

 fessional cheinical work gratuitously, or at purely nominal 

 fees. In the endeavour to help dairy farmers, the board has 

 induced the colleges, which are maintained by grants for 

 technical education, for the benefit of a particular class, to 

 compete with professional chemists, particularly those re- 



NO. 1845, VOL. 71] 



tained by the agricultural associations, at the expense of 

 the general public. The president held that the colleges 

 need the grants for the promotion of the education of 

 farmers in the science and practice of agriculture, without 

 diverting them to other purposes. It is for them to instruct 

 the farmers in agricultural chemistry. 



SOCIETIES AND ACADEMIES. 



Lo.NDON. 



Royal Society, February 2. — " The Theoryiof Photographic 

 Processes: on the Chemical Dynainics of Development." 

 By S. E. Sheppard and C. E. K. Mees. 



If a photographic plate be exposed to light and 

 developed, the transparency to light of the silver de- 

 posited is related to the mass thereof by the equation 

 D=— logijT, where D (termed the density) is proportional 

 to the mass of silver per unit area. This relation has been 

 confirmed with great care for densities varying from 0.5 to 

 3.5, and for the plates and developer used a density of i.oo 

 corresponded to 0.0103 1 gram of silver per 100 sq. cm. 

 This quantity is termed P, the " photometric constant " of 

 the deposit. 



A study of the relation of the density to the time of 

 development resulted as follows : — 



(a) The silver deposited increases rapidly at first, then more 

 slowly, and finally tends to a limit. 



(b) This limit depends only on the exposure. 



(c) The velocity depends on the concentration of the 

 reducer. 



(d) A soluble bromide reduces the velocity, but the " slow- 

 ing off " with time is not so rapid. 



A theoretical investigation of development based on the 

 theory of reaction-velocities in heterogeneous systems led 

 under certain conditions to the equation dD/d/ = /t(Doo - D), 

 w Dr^ is the limiting density, D that at the time (. On 



integration this leads to the expression 



i/( log D5o/D:<5 -D = k; 



(Dog— D) is then the reacting surface. 



K was experimentally shown to be constant. 



Further, as k is theoretically A/5 a, where A is a 

 diffusion-constant, 5 the diffusion path, and a the concen- 

 tration of the reducer, the velocity should be proportional 

 to this, which was experimentally found. 



The addition of alkaline bromides graduallv alters the 

 course of the reaction, introducing an induction period, but 

 for the " maximum " velocity icXlog Br = a constant. 



The value of k depends greatly on the physical condition 

 of the plate, diminishing with keeping, probably from 

 lowered diffusivity. 



An important deduction from the development formula is 

 that the ratio of the densities due to two exposures is con- 

 stant and independent of the time of development, which was 

 confirmed. 



For a series of increasing exposures for a certain range 

 Hurter and Driffield showed that D = 7(log E/i), where y is 

 development-constant. 



Hence as 7 is proportional to D, and as 



i;( log D«,/D« -D = K, 



therefore i ( log 7oo/7oo -7=", an expression which may 

 be used to compare the velocities of different developers. For 

 ferrous oxalate, citrate and fluoride the following table was 

 obtained : — 



Developer Rel.itive efficiency 



Ferrous citrate 1.00 



Ferrous fluoride 2.95 



Ferrous oxalate 4S.7 



Further communications are to be made on the influence 

 of temperature, of soluble bromides, on the reversibility of 

 the reaction, on the microscopy of, and on the exposure and 

 development, nature and destruction of the " latent image." 



The obiect of the investigation is to make the study of 

 development quantitative and to bring it in line with general 

 physicochemical theory. 



