102 



NATURE 



[April 17, 1913 



I may add that one obtains quite similar phenomena 

 with ordinary light and two ordinary (200 lines per 

 millimetre) gratings, when the incident beam forms 

 similar angles of incidence with the plane of the 

 gratings. M. de Brogue. 



Increase of Definition in a Moving Telescope. 



I have received several suggestions, for which I 

 wish to express here my indebtedness, as to the prob- 

 able explanation of the increase of definition in a 

 moving telescope, referred to in my letter in Nature 

 of March 27. They are chiefly based on the principle 

 of " contrast " as described by Mr. G. W. Butler in 

 Nature of April 10, but Mr. W. H. Robinson, of 

 Oxford, attributes the increase of definition to "averted 

 vision," by which a faint source of light is better 

 seen if the eye be directed a little on one side of it. 

 This, at first, seemed to me the correct explanation, 

 the more satisfactory that it involves but a well- 

 known physiological property of the eye. By moving 

 the telescope the object is continually eluding the eye, 

 and visibility by continuous unconscious "averted 

 vision " would be the result. I, however, satisfied 

 myself that there must be some other cause, as a 

 deliberate use of " averted vision " failed entirely to 

 show me the time-ball when I tried it after receiving 

 Mr. Robinson's letter, while I noticed that, as soon 

 as the sweeping motion had begun, it was plainly 

 visible bv direct vision, my eye following it all the 

 time. Mr. Butler's suggestion seems therefore more 

 plausible, although less definite. 



M. E. J. Gheury. 



Woolwich Polytechnic, April 15. 



THE NINTH INTERNATIONAL CONGRESS 

 OF ZOOLOGY AT MONACO. 



THE ninth International Congress of Zoology 

 terminated its session under the presidency 

 of his Serene Highness the Prince of Monaco at 

 Monaco on Saturday, March 29. Altogether, the 

 meeting was an unqualified success, not only on 

 account of its numbers, which, as already stated, 

 were greater than on any previous occasion, but 

 also for the general interest of the contributions, 

 which, although no single one can be selected as 

 absolutely outstanding, were all of very high 

 quality, and demonstrated the result of much 

 serious and useful work by zoologists during the 

 past three years. The beauties of the C6te 

 d'Azur doubtlessly attracted many from northern 

 lands, and although the weather was not all that 

 could be expected for the Riviera at this season, 

 yet the rather copious rainfall settled and washed 

 away the dust and refreshed the herbage, which 

 was the more brilliant during the intermittent 

 periods of bright sunshine. The chief attraction, 

 however, was the noble Oceanographical Museum, 

 which crowns the cliffs of the rock upon which the 

 town of Monaco with its palace is situated, and 

 the fact that the congress was to hold its chief 

 meetings within its precincts, with its founder as 

 their president. 



The opening reception in the museum, the hold- 

 ing of many of the meetings of the congress 

 within its walls or only across the other side of 

 the road at the Lyceum, and the fact that mem- 

 bers were entitled to visit all its galleries and its 

 XD. 2268, VOL. Ql" 



aquarium at any time during the whole congress 

 enabled everybody to become thoroughly ac- 

 quainted w-ith the museum and its interesting col- 

 lections. Since its opening in 1910 there have 

 been great developments and additions, thanks to 

 the indefatigable energy of Dr. Jules Richard, 

 its able director, and his assistants. A very full 

 account of the museum was given soon after its 

 opening in the columns of Nature by Mr. J. Y. 

 Buchanan ; it is not, therefore, necessary to repeat 

 what he has said, but since that time there have 

 been many developments, and among others the 

 opening up of a large new gallery in the western 

 wing of the building. Zoologists were especially 

 delighted, not only in seeing the excellent 

 cetacean collection — whales mostly captured by 

 the Prince himself — but also the really marvellous 

 collection of well-mounted deep-sea fishes, which 

 were familiar to many as figures, but the original 

 specimens of which they now saw for the first 

 time, and the same may be said of the inverte- 

 brates. A particularly useful and instructive ar- 

 rangement is that side by side of each specimen is 

 placed, where possible, the original painting of 

 the animal taken from the fresh specimen, or the 

 reproduction of such a coloured drawing as pre- 

 sented in the unique plates appearing in the 

 Prince's publications. This is specially valuable, 

 since it is impossible to preserve the original 

 colours of animals in alcohol and because a better 

 idea of the form of the fresh animal is given. 



Besides the Prince's collections were also shown 

 the first fruits of exchange with outside collec- 

 tions, and notable among these was a case contain- 

 ing many of the deep-sea and shallow animals 

 taken by the Scotia. There is also a well-mounted 

 case of penguins taken by the French Antarctic 

 Expedition, as well as seals, birds, and eggs 

 taken by the Scotia in the antarctic regions. 



The collection of instruments and various forms 

 of fishing appliances, nets, trawls, dredges, traps, 

 hooks, &c, used not only for scientific but also for 

 economic fishing, was also a source of attraction, 

 and not least of all the aquarium with its wonder- 

 ful living forms of Mediterranean fishes and in- 

 vertebrates, each more wonderful than its neigh- 

 bour, and which only those who had previously 

 visited such stations as Yillefranche and Naples 

 had seen before, but were more than ready to see 

 again. 



Some days before the opening of the congress 

 many zoologists made their appearance, and on 

 Monday, March 24, practically the complete roll of 

 723 members, including more than eighty British 

 representatives, was signed, and members had 

 received their insignia, cards, and papers. On 

 Tuesday afternoon there was a meeting of the 

 permanent committee for the election of vice- 

 presidents of the congress and presidents of the 

 sections. Lord \.Ya!singham being' chosen first 

 vice-president. At 6 p.m. the congress was 

 formally opened by the Prince, who, dressed in the 

 official uniform of the Institut de France, 

 delivered his inaugural address. The president 



