202 



NATURE 



[June 28, 1894 



which gives / in terms of the coefficient of expansion of 

 (<^) the cell material, 7I the glass, and (a) the material 

 for the blocks. It will be seen from the formula that 

 the shorter the blocks the more equal must be the co- 

 efficients of expansion of the glass and cell material, and 

 also the greater the relative distance between the co- 

 efficients of expansion of the blocks and cell material. 



Dr. Steinheil, as an example, determines the length of 

 these blocks for an objective of 50 cm. aperture, the 

 lenses being composed of common flint silicate marked 

 0.544 in the Jena glass factory, and common crown 

 silicate marked O.1022. 



If the material for the blocks used be of zinc (coefficient 

 of expansion = (7 = 000002918), then their length, adopt- 

 ing for the tiint glass (544) the value 7 = 000000788 and 

 for the cell material the value (^ = 000001061 for their 

 coefficients of expansion, is given by the equation 



/='°6'- 788^^73 = 0. , 

 291S-1061 1857 



Similarly for the crown glass, the coefficient of which is 

 0-00000954, we obtain the length of its blocks 



/=o'0576. 



As the radii of the glass discs are the same and equal 

 to 25 cm., the lengths of the blocks for each of the lenses 

 must be o'i47 x 25 cm. and 00576 x 25 cm. or 3675 cm. 

 and 144 cm. 



Ur. Steinheil proposes that for each lens three blocks 

 should be used and placed at intervals of 120^ round the 

 circumference of the discs, the blocks fitting tightly be- 

 tween the discs and the sides of the cell. It might at 

 first be thought that such tight-fitting as seems necessary 

 could not be exactly enough done, but it is stated that 

 accuracy in the length of the zinc block to i mm can be 

 safely depended on, and the danger of strain by eliminat- 

 ing the disturbances of centering thereby reduced to a 

 minimum. 



That this new mounting for object-glasses has many 

 points in its favour cannot be denied, but it is in such 

 questions as these that we must look to the results after 

 the method has been practically applied. Thus, practice 

 would better settle the proper number of blocks for each 

 lens ; three seem at first sight somewhat too few, and 

 might lead to local strains due to the weight of the 

 lenses, whereas such strains must be avoided in anv sort 

 of cell. W. J. S. LuCKYER. 



NOTES. 



\Vf. are requested to slate that a volume conlainini; a memoir 

 of the late Dr. Geo. J. Romanes, F.R.S., will be published. 

 Tho»e who possess letters of general interest wiilten by him 

 are ie'|uested to forward them to Mrs. Romanes, St. Aldatc's, 

 Oxford. The letters will be leturned directly their contents 

 baTe been noted and copies made. 



A Grace of the Senate of the University of Dublin has been 

 pused, conferring the degree of Doctor of Science upon Mr. 

 Daniel Morris, C.M.G., Asiistant-Dircctor of the Royal 

 Gardens at Kcw. 



Prok. Karl Glsslniiauer, of Prague University, h.os been 

 appointed to the chair of Surgery at Vienna, in succession to 

 the late Prof. Billiolh. 



A Reuter telegram states that at a meeting of leading citizens 

 held at Toronto on June 23, it was unanimously decided to 

 invite the Uritisb AMocialion to hold the meeting there next 

 year. 



The Council of University College, Liverpool, have ap- 

 pointed Or. A. M. Paterson to the " Derby " Professorship of 

 Anatomy, and Prof. R. W. IJoycc to the chair of Pathology 

 recently endowed by Mr. George Holt. 



NO. 1287, VOL. 50] 



Dr. Augustus Schloesser, assistant to Prof. Henderson in 

 the chemical department of the Glasgow and West of Scot- 

 land Technical College, has been appointed to the Principalship 

 of the Storey Institute, Lancaster, rendered v.icant by the 

 resignation of Dr. G. S. Turpin. 



A KINDLY and appreciative letter, by Prof. Poulton, F.R. S., 

 on some incidents in the life of the Lite Prof. Romanes, ap- 

 peared in the Times of June 19. The July number of Science 

 Gossip contains an obituary notice of the lamented investigator, 

 together with his portrait. 



The Cracow Academy of Sciences have awarded the Coper- 

 nicus Prize of five hundred florins, founded by the town of 

 Cracow, to Prof. Louis Birkenmajer, for his work " Sur la 

 temperature des lacs des Tatres." .\ prize of one thousand 

 francs (Priz Majer) is offered for the best work on "La Clima- 

 tologie des pays Polonais " ; papers to be sent in before December 

 31, 1896. 



A SEVERE earthquake disturbance was experienced at Oran, 

 Algeria, at about one o'clock on the morning of the 19th inst. 

 The duration of the shock is said to have been four seconds. 



A SPECIAL meeting of the Chemical Society will be held 

 this evening, at nine o'clock, at the Royal Institution, when 

 Prof. Dewar will lecture on " Phosphorescence at very low 

 temperatures." 



The meeting of the Museums Association, now being held in 

 Dublin, was opened on Tuesday with an address by the 

 President, Dr. Valentine Ball, C.B., F.R.S., on "The 

 Museums of Dublin." 



I.\ the House of Commons on Tuesday, Colonel Howard 

 Vincent .isked the Home Secretary whether he had decided to 

 adopt in the Metropolitan and City Police districts, and in the 

 provinces, the recommendations of the committee appointed to 

 inquire into the system of identifying criminals by measure- 

 ment, invented by M. Bertillon, of Paris, and the fingerprint 

 test of Mr. Francis Galton ; and, in such case, if, in order to 

 facilitate research into the judicial antecedents of international 

 criminals, the registers of measurements would be kept on the 

 .same plan as that adopted with such success in Frnncr, as also 

 in other continental countries. In reply, Mr. .Vsquith said that 

 the recommendations of the committee had been adopted, in- 

 cluding the recommendations as to the mode of keeping the 

 register. 



In connection with the Antwerp Exposition, a Congress has 

 been arranged, under the auspices of the Socitite Royale de 

 Geographic d'Anvers, having for its object the discussion of 

 matters relating to the atmosphere. The Congress will beheld 

 on August 16, 17, and iS. The papers will be classified 

 into two sections, one dealing with atmospheric move- 

 ments, while the other is concerned with aerodynamics. 

 The former section is divided into four parts as follows : — 

 (l) General theory of atmospheric currents and the causes 

 which affect them. (2) Methods of observation at different 

 altitudes. (3) Instruments of observation and for automatic 

 registration. (4) Maps of permanent and of variable atmospheric 

 currents, and a comparison of them with ocean currents. In 

 the .lerodynamic section the subjects dealt with will be : — 

 (1) The measurement of the velocity of wind. The action of 

 wind on a plane normal surface and on nn inclined surf.icc will 

 be considered, and the friction of air. Experimental apparatus 

 is also included in this division, and the elTecls of wind on 

 buildings, bridges, towers, ^;c. Aeroplanes, windmills, and 

 turbines are classified under the motive power of wind, while 

 transport by land, sea, and air are arranged in a sub group of 

 questions relating to the resisting power of air. The subjects 

 of the second part of the second section are the special applica- 



