October 23, 1890] 



NATURE 



6:, I 



The necessary cooling may be estimated in the following way : 

 Supposing the solution to be a mixture, and to be cooled below 

 its normal freezing-point, then, on solidification, the temperature 

 would rise to this point, but if this solidification involved a 

 chemical decomposition which absorbed x cal, the rise of 

 temperature would be thereby reduced, the reduction thus 

 caused amounting K.o x ~ the heat capacity of the solution. As 

 the heat absorbed in the decomposition of the various hydrates 

 of sulphuric acid is known, we can calculate the lowering pro- 

 duced by their presence. 



In Cols. II., III., and IV., I have given the depression due 

 to the three above-mentioned causes in the case of certain solu- 

 tions. Col. V. containing their sum ; and it will be seen what a 

 small proportion of this total lowering can be attributed to 

 purely chemical causes. With most solutions it does not exceed 

 10 per cent, of the total, and with weak solutions, such as are 

 generally used in freezing-point determinations— say 5 per 

 cent. — it amounts to considerably less than o°*i ; this, too, in 

 the case of sulphuric acid, where the heat of formation of the 

 higher hydrates is greater than with any other known substance. 



The reason, therefore, why the deviations from constancy are 

 so small as to have escaped detection hitherto, and the reason 

 why solutions behave almost as if their chemical nature was 

 non-existent, becomes apparent ; but this near approach to 

 constancy and regularity, instead of proving the correctness of 

 the physical theory and giving a death-blow to the chemical 

 theory, is really one of the strongest arguments which can be 

 adduced in favour of the latter. If the hydrate theory is right, 

 the influence of hydrates must often be nearly inappreciable. 



But it is not only a general concordance between the found 

 and calculated magnitude of the irregularities which the hydrate 

 theory is capable of affording, but a concordance so exact that 

 the precise value of the deviation at any point may be calcu- 

 lated. In Col. Vr. 'of Table II. are given the observed 

 freezing-points of the solutions, and these show an average 

 difference of but 0° '004 for the three weaker solutions, and 0° -06 

 for the four stronger solutions, from those calculated (Col. V.). 

 The last two columns exhibit this concordance in a different 

 manner ; from the observed freezing-point we can calculate the 

 composition of the hydrates which must exist in the solution 

 (Col. VII.), and these are found to agree so fully with those 

 indicated by the examination of the curved figures representing 

 various properties of the solution (Col. VIII.) that the maximum 

 difference between the two is only 0-48 in the percentage of 

 acid present. 



When we can by simple calculations, based on one series of 

 determinations, prove that the hydrates in solution must be the 

 same as those which totally independent experiments have led 

 us to suppose, we have, I think; arrived "at proof as nearly 

 absolute as it is possible to conceive ; and, if I have succeeded 

 in showing that this proof may be accepted without in any way 

 rejecting the facts on which the advocates of the osmotic pressure 

 theory rely — approximate constancy, approximate regularity, and 

 approximate similarity between dissolved and gaseous matter — I 

 shall feel that I have done far better work than the mere 

 establishment of the hydrate theory, by pointing out a possible 

 modus Vivendi for both theories almost in their entirety, and by 

 helping to break down that wall of separation between physicists 

 and chemists which is fast crumbling into dust. 



Spencer Umfreville Pickering. 



' The actual total has been increased by 10-4 per cent, of its value to give 

 the figures quoted in these five cases, for reasons which will be given else- 

 where. Some of the numbers in this table may be subject to slight correc- 

 tions, as they have been quoted in the absence of the original calculations. 



A TEACHING UNIVERSITY FOR LONDON. 



'T'HE following letter has been addressed to the Lord President 

 -*• of the Privy Council : — 



My Lord, — We, the undersigned, the President of University- 

 College, London, and the Principal of King's College, London, 

 beg leave to address your Lordship in reference to the joint peti- 

 tion from the Councils of our two Colleges for the incorporation 

 of a Teaching University in London, which has for some time 

 been before the Privy Council. Your Lordship had the good- 

 ness to receive a deputation from the Councils of our two Col- 

 leges in July 1889 ; and your Lordship then intimated your 

 judgment that the University of London should be allowed a 

 reasonable time in which to propose a new charter in accordance 

 with the recommendations of the Royal Commission on the 

 question of a Teaching University in London. In obedience to 

 this intimation from your Lordship, our Councils have, at the 

 request of the Senate, entered into negotiation with them, and 

 have consented, subject to the satisfactory settlement of some 

 points affecting the Faculties of Law and Medicine, to a scheme 

 for our union with the University, embodying a separate system 

 of graduation for our students in the Faculties of Arts and 

 Science. We desire that power should be reserved in certain 

 events to make similar arrangements in regard to the Faculty of 

 Law. With respect to medicine, the Senate have stipulated 

 that they should be at liberty to make different arrangements, 

 separately from our Colleges; andin the absence of opportunities 

 for conference with the other institutions specially interested in 

 this Faculty, we have not thought fit on this ground to break off 

 the negotiations ; but we reserve power to reconsider our posi- 

 tion, if arrangements are contemplated by which it would be 

 seriously affected. We claim, further, as essential to the effL- 

 ciency of our teaching in science, that our medical students, for 

 the purpose of their examination in pure science, known as the 

 "Preliminary Scientific Examination," shall be considered as 

 belonging to the Faculty of Science on the teaching side of the 

 University, and not to a separate Faculty of Medicine. 



Having been informed that urgent protests are raised by Uni- 

 versity Colleges in the country, particularly at Birmingham, 

 against influence being given to London Colleges in the Senate 

 while they are excluded, we beg to remind your Lordship that 

 the amalgamation of the proposed Teaching University for 

 London with the existing University was not our proposal, but 

 has been, thus far, accepted by us in deference to the principal 

 Report of the Royal Commissioners. We consider that, if this 

 amalgamation is effected, we are entitled to a representation on 

 the governing body of the reconstituted University proportionate 

 to our concern in University teaching for London, considered as 

 one of its two spheres of work ; and that the nature of the case 

 does not admit of a similar effective representation of institutions 

 elsewhere. If this reconstitution of the existing University 

 should be found, by reason of such opposition, or for any other 

 reason, impracticable, we desire to be replaced in our original 

 position, as petitioners for the establishment in London of a 

 Teaching University upon the lines of our petition presented in 

 1887, and of the draft charter thereto appended, to which, in 

 that case, we still respectfully adhere. 



We have the honour to remain, your Lordship's obedient 

 humble servants, 



John Eric Erichsen, 



President of University College, London. 

 Henry Wage, 



Principal of King's College, London. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — The election of a Professor of Mechanism and 

 Applied Mechanics, in succession to Prof. James Stuart, will 

 take place on November 12. The names and testimonials of 

 candidates are to be sent to the Vice-Chancellor by Saturday, 

 November 8. The electors are the Vice-Chancellor, Mr. W. 

 Airy, Dr. Besant, Sir F. J. Bramwell, Dr. Cayley, Mr. H. 

 Darwin, Mr. Martin, Dr. Phear, and Lord Rayleigh. The 

 stipend is ;[^700. The Senate has approved a new scheme for 

 the management of the department, under which the Professor 

 is directly responsible for the carrying on of the workshops. 



Mr. Chaplin, the President of the Board of Trade, has pro- 

 posed to the Chancellor that the University should undertake 



NO. 1095. VOL. 42"] 



