lOi 



KNOWLEDGE & SCIENTIFIC NEWS. 



[May, 1905. 



The OpticaLl Convention. 



The programme of arrangements for the Convention is 

 now beginning to assume a definite shape, and particulars 

 as to what is at present proposed will no doubt be of interest. 

 The Convention will be formally opened with an 

 address from the President, Dr. R. T. Glazebrook, 

 M..\., F.R.S., Director of the National Physical Labora- 

 tory, on the evening of Tuesday, May the 30th, and the 

 gathering will extend over the four following days, up to 

 and including Saturday, June the 3rd. The mornings 

 will be devoted to papers and discussions, and in view of 

 the interesting series of papers already announced, there 

 is no doubt that this most important section of the pro- 

 ceedings will result in valuable contributions to Optical 

 science, and will fulfil the aims which those who have 

 been active in promoting the Convention have set before 

 them. In addition to the papers, demonstrations of 

 apparatus of special mterest will be given in the after- 

 noons in the Laboratories of the Department of Technical 

 Optics of the Northampton Institute. 



The Exhibition of optical and scientific instruments 

 will be held in the large Hall of the Northampton 

 Institute, and will be open daily to the public from 12 to 

 10 p.m., between May 31st and June 3rd inclusive. The 

 charge for admission will be one shilling during the day, 

 and si.xpence after 7 p.m. 



The Catalogue is now in active preparation. The 

 arrangement made by the " Exhibition and Catalogue" 

 sub Committee that each section should be dealt with by 

 an expert in the construction of the instruments repre- 

 sented in the section, together with an independent 

 scientific member of the Committee, will ensure that all 

 classes of instruments shall be adequately dealt with and 

 described. It is proposed to fix the sale price of the 

 Catalogue, which will be a volume of some 300 quarto 

 pages, at is. 6d. ; while in large numbers of 100 and 

 upwards, the Catalogues will be issued to firms at a cost 

 of IS. each. The Hon. Secretary would be glad to hear 

 at once from firms wishing to take a number of the Cata- 

 logues for private distribution. 



Arrangements for promoting the social interest of the 

 gathering, and for providing for the comfort and conveni- 

 ence of members attending from outside London, are now 

 being considered by a " Hospitality and Entertainments " 

 sub-Committee. In addition to the Presidential address, 

 to be given on the Tuesday evening, which has already 

 been mentioned, there will be an evening lecture by Pro- 

 fessor Silvanus P. Thompson, D.Sc, F.K.S., on " The 

 Polarization of Light by Nicol Prisms and their Modern 

 Varieties." On a third evening it is proposed to hold a 

 Conversazione; and for the Saturday afternoon, a visit 

 to the National Physical Laboratory at Teddington is 

 proposed, at the kind invitation of Dr. Glazebrook, the 

 President of the Convention. 



Further particulars will be announced later, when the 

 programme is more definitely settled. It will greatly 

 help towards ensuring the social success of the Coven- 

 tion if intending members will send in their applications 

 at once ; the subscription for membership is 5s. The 

 Hon. Secretary, Mr. F. J. Selby, Elm Lodge, Tedding- 

 ton, Middlesex, will be glad to hear from those wishing 

 to join the Convention. 



The " Local Societies and Representatives " sub- 

 Committee is dealing with the question of facilities for 

 the attendance of visitors from a distance. The Secre- 

 tary of this Committee is Mr. W. Rosenhain, B.A., 443, 

 Gillott Road, Edgbaston, Birmingham. Mr. Rosenhain 

 will be glad to give information in answer to enquiries, 

 and will also be ready to receive applications for mem- 

 bership of the Convention. 



A Curiovis Induction 

 Experiment. 



By Ch.^klks E. BtNii.\.\i. 



The following curious experiment, simple as it is, will 

 probably be new to most readers. Place on a level table 

 two glass tumblers which have been first freed from any 

 superficial moisture by warming them near a fire. Lay 

 a book on each tumbler, the two books being of similar 

 size. The longer sides of the books should be parallel 

 with each other, and the supporting tumblers should he at 

 such a distance apart that the two books are about one 

 inch apart. Place a third book of the same size on a 

 sheet of glass, which must also have been well warmed 

 at the fire. The third book must be laid so that it rests 

 crosswisT over the other two. with the sheet of glass 



J) 



FiK. I. A and li the two lower hook.%. C the upper book, reslinK ntl 

 the Klas» plate D, and carrying a small coin, laid on the top of 

 the book. 



between them, as shown in fig. i, in which the dotted 

 line represents the piece of glass, the proportionate size 

 of which is thus indicated. On the top book lay a penny, 

 as indicated in the diagram, to act as a conductor for 

 drawing ofl' the electric sparks which are to be produced 

 by this singular arrangement. Now taking the glass 

 carrier, and holding it near tiie front edge, mme it, with 

 its book, horizontally right and left, so that the upper 



c ■■ 



A 



(. 1. A and II the two lower hof.kt. C t 

 pnrtlne kIo>* plate not nluiwn> In It* exi 

 »ame book In its extreme riKl'l roHilion. 



lelt position. C the 



