Errata in Vol. 49. 



Page 457, line 9 from bottom, for read O. 



— — line 7 from bottom, for C Q read O Q. 



— 466, lines 5 and 6, for intersection read intersections, and dele and to the 



origin. 



— — line 13, for flow-line read straight line. 



— 471, first line of § 42, for § 39 read § 38. 



Plate IX. fig. 3. — The middle point of the straight line A B should be marked O. 



Plate X. fig. 6. — The circle should not extend into the left-hand half of the 



figure, or should be shown there only by a dotted line. 



RECENT CHEMICAL DISCOVERIES. 



Now ready, in One thick Volume, 8vo, price 42s. cloth, 



SECOND SUPPLEMENT TO WATTS'S DICTIONARY OF CHEMISTRY, 



Bringing the Record of Chemical Discovery down to the end of the year 1872; 



including also the more Important Additions to the Science made in 1873. 



By HENRY WATTS, B.A., F.R.S., F.C.S., 



Assisted by eminent Scientific and Practical Chemists. 



The ORIGINAL WORK, in Five Volumes, 8vo, price £7 3s. 



The FIRST SUPPLEMENT, One Volume, 8vo, price 31s. 6d. 



London: Longmans and Co. 



HELMHOLTZ ON TONE. 



Now ready, in 1 vol. 8vo, price 36s. cloth, 



ON THE SENSATIONS OF TONE 



As a Physiological Basis for the Theory of Music. 



By HERMANN L. F. HELMHOLTZ, M.D., 



Professor of Physics in the University of Berlin. 



Translated, with the Author's sanction, from the Third German Edition, with 



Additional Notes and an Additional Appendix, by 



ALEXANDER J. ELLIS, F.R.S. &c. 



London : Longmans & Co. 



LOAN EXHIBITION OF SCIENTIFIC APPARATUS AT THE SOUTH 



KENSINGTON MUSEUM. 

 The Exhibition will open on the 1st April, 1876, and will remain open until the 

 end of September, after which time the objects will be returned to the owners. 



It will consist of instruments and apparatus employed for research and other 

 scientific purposes, and for teaching. It will also include apparatus illustrative 

 of the progress of science, and its application to the Arts, as well as such as may 

 possess special interest on account of the persons by whom, or the investigations 

 in which, it had been employed. The precise limits will be found further detailed 

 under the several sections in which the syllabus has been arranged for conveni- 

 ence, and for the information of exhibitors, rather than as a matter of scientific 

 classification. Models, drawings, or photographs will also be admissible where 

 the originals cannot be sent. And the apparatus may, in certain cases, be arranged 

 in train as used for typical investigations. 



The syllabus and the forms on which to enter descriptions of objects offered 

 for exhibition may be obtained on application to the Director of the South Ken- 

 sington Museum, London, S.W. These forms should be filled up and returned 

 as soon as possible, so that exhibitors may receive early intimation as to the ad- 

 missibility of the objects they propose to send. 



Whilst every care is taken of objects lent for exhibition, the Science and Art 

 Department cannot be responsible for loss or damage. 



The Committees will have the right of rejecting any object that it may be 

 thought unadvisable to exhibit. 



^ The cost of carriage of all objects selected for exhibition will be defrayed by 

 the Science and Art Department. 



It is hoped that institutions or individuals having instruments of historic in- 

 terest will be good enough to lend them. 



By order of the Lords of the Committee of Council on Education. 

 [ADVERTISEMENTS continued on 3rd page of Cover. 



