498 



NATURE 



\_Marc/i 27, 1879 



A REVISED schedule of subjects in natural science for the 

 ordinary B.A. degree at Cambridge has just been issued. This 

 is for the third or final examination, and a pass in one subject is 

 sufficient to give a degree. Is it supposed at Cambridge that a 

 year is to be fully employed in dealing with botany in an 

 eUmeutary manner? The schedule i-ays the questions (all 

 elementary) will include the description and classification of 

 plants ; the form, structure, and development of stem, root, leaf, 

 flower, and fruit ; inflorescence, cross-fertilisation, germination, 

 and nutrition. Twenty-one " natural orders " are specified for 

 special attention, including one cryptogamic group, Filices. This 

 seems a vague syllabus, not likely to encourage the study of 

 botany. How much and how little knowledge of physiology 

 and histology will satisfy such terms as " nutrition," " structure " ? 

 No doubt the present is better than the old in omitting to insist 

 on technical terms, some of them antiquated. But cannot more 

 definite requirements be suggested for ensuring some practical 

 insight into vegetable life on the part of the man who is to be 

 stamped as an elementary botanist? Surely the best way is to 

 let the knowledge be good, and sound, and practical, as far as it 

 goes, giving some training in scientific method, and capable 

 of further development in after life. We believe many would 

 welcome a change giving the ordinary B.A. for a lower 

 standard of attainment in the first part of the natural science 

 tripos, thus doing away with the recognition of dilettante 

 work in a single subject as a sufficient basis for a B.A. degree. 

 A very satisfactory schedule is presented for zoology, requiring 

 a knowledge of the anatomy of certain selected principal types, 

 as well as the characters of orders, and the comparative anatomy 

 and functions of the systems and organs as exemplified in the 

 animal kingdom. Further, the general development of the 

 embryo chick, the leading facts and conclusions respecting the 

 geographical distribution of animals are included in the subjects. 

 The schedule is to be discussed next Saturday. 



The Cambridge Council of the Senate has framed a draft 

 statute to carry out the grace passed in December last in favour 

 of the appointment of a general Board of Studies, representative 

 in character, to report upon the proposals of each special board 

 of studies as they arise, and so aid in holding the balance among 

 the various interests concerned. The draft statute provides that 

 the new Board shall consist partly of persons appointed on the 

 nomination of the Boards of Studies, but abundant freedom is 

 left to the senate to add other members and to vary from time 

 to time the composition, mode of appointment, and duties of the 

 new board. 



At the next meeting of the Governors of Addenbrooke's Hos- 

 pital Mr. J. "W. Cooper will propose : That a memorial be pre- 

 sented to Her Majesty's Commissioners for the University of 

 Cambridge, under the seal of the Governors, representing that 

 Addenbrooke's Hospital is extensively used as a place of study 

 by the Medical Students of the University ; that it is essential in 

 the interests of the Medical School that it should not cease to be 

 a recognised place of medical study ; and, further, that as large 

 endowments have been left to various colleges for the promotion 

 of medical study, some adequate endowment should be made for 

 Addenbrooke's Hospital out of the funds at the disposal of the 

 Commissioners. There cannot be much chance of success for 

 such a proposal unless it be made more definite. The hospital 

 can only properly benefit by educational endowments by being 

 the locus of the study and appliances of research in therapeutics, 

 sanitation, and pathology. 



Geological students at Cambridge will have plenty of work 

 provided for next term. Prof. Hughes will give one course on 

 the geology of the neighbourhood of Cambridge, and another 

 stratigraphical course, beginning with the Permian, and ascending. 

 Prof. Bonney will continue his lectures on elementary physio- 

 graphy, and will give weekly demonstrations on microscopic 

 lithology. Mr. Tawney will be demonstrating the principal 

 genera of fossil invertebrata ; and both he and Dr. R. D. 

 Koberts will give practical instruction in petrology. Lectures 

 begin April 25. The first geological excursion of the term is 

 fixed for Saturday, May 3. 



Mr. Thomas W. Bridge, B. A., of Trinity College, Cambridge, 

 and Demonstrator of Comparative Anatomy in the University of 

 Cambridge, has been appointed to the Professorship of Zoology 

 at the Royal College of Science at Dublin, vacant by the 

 resignation of Dr. Leith Adams, F.R.S. 



SOCIETIES AND ACADEMIES 



LO.NDON 



Royal Society, March 13. — " The Contact Theory of Voltaic 

 Action," No. III. By Professors \V. E. Ayrton and John Perry. 

 Commimicated by Dr. C. W. Siemens, I'^.R.S. 



The authors commence by referring to the experiments that 

 had been made prior to 1876, on the difference of potentials of a 

 solid in contact with a liquid, and of two liquids in contact with 

 one another, and they point out that : — 



1. The earlier experiments were not carried out with apparatus 

 susceptible of giving accurate results. 



2. Owing to the incompleteness of the apparatus assumptions 

 had to be made not justified by the experiments. 



3. No direct experiments had been performed to determine the 

 difference of potential of two liquids in contact, with the excep- 

 tion of a few by Kohhausch, using a method which appeared to 

 the authors quite inadmissible as regards accuracy of result. 



In consequence of this great vagueness existed as to whether 

 the contact difference of potentials between two substances, when 

 one or both were liquids, was a constant depending only on the 

 substances and the temperature, or whether it was a variable 

 dependent upon what other substance was in contact with either. 

 Some authorities regarded it as a variable, Gerland considered 

 he had proved it to be a constant, but first, the agreement of the 

 value of the electromotive force of each of his cells wiih the 

 algebraical sum of the separate differences of potential at the 

 various surfaces of separation, and which was the test of the 

 accuracy of his theory, was so striking, and so much greater than 

 polarisation, &c., usually allows one to obtain in experiments of 

 such delicacy, that one could not help feeling doubtful regardii^ 

 his conclusions ; secondly, his apparatus did not allow of his 

 experimenting with two liquids in contact, consequently he could 

 not legitimately draw any conclusion in this latter case. And 

 although Kohlrausch had made some few experiments on the 

 difference of potentials of liquids in contact, still since he em- 

 ployed moist blotting-paper surfaces instead of the surfaces of 

 the liquids themselves, the authors considered for that reason 

 alone, if for no other, that his results did not carry the convic- 

 tion the distinguished position of the experimenter might have 

 led them to anticipate. 



They therefore designed a method and an apparatus for carry- 

 ing it out, by means of which they could measure the difference 

 of potentials, in volts, at each separate contact of dissimilar 'sub- 

 stances in the ordinary galvanic cells, from which they could 

 ascertain whether the algebraical sum of all the contact differences 

 of potential was, or was not, equal to the electromotive force of 

 the particular cell in question. From the results they obtained, 

 and which are given in Papers Nos. I. and II., Proc. Roy. Soc, 

 No. 186, 1878, they concluded within the limits of their experi- 

 ments that if AB, BC, CD, &c., were the contact differences of 

 potential measured separately of the substances A in contact with 

 B, and neither in contact with any other conductor, B in contact 

 with C, &c., then, any one or more of the substances being solid 



or liquid, if any number A, B, C A' were joined together, 



and the electromotive force of the combination AK, measured, 

 the following equation was found true : — 



AK = AB-l-BC-fCD-f -J-JK, 



which proved that each surface of separation produced its effect 

 independently of any other. 



Their method, by which any single contact J difference of 

 potentials was measured, was as follows : — Let 3 and 4 be two 

 insulated gilt brass plates connected with the electrodes of a deli- 

 cate quadrant electrometer. Let I under 3, and 2 under 4 be 

 the surfaces whose contact difference of potential is to be mea- 

 sured ; 3 and 4 are first connected together and then insulated, 

 but remain connected with their respective electrometer quadrants. 

 Now I and 2 are made to change places with one another, 1 

 being now under 4 and 2 under 3, then the deflection of the 

 electrometer needle will give a measure of the difference of 

 potentials between I and 2. 



The apparatus employed by the authors in the present investi- 

 gation is then explained in detail, and it is shown how, by im- 

 proving on their earlier form, they have removed a difficulty 

 which formerly existed, and which prevented their previously ex- 

 perimenting on pairs of substances having very different weights, 

 such as a vessel of mercury and a sheet of metal. 



The authors explain that the results they have obtained in this 

 investigation have divided themselves into three groups : — 



