no 



KNOWLEDGE 



[May, 1902. 



SGveriil iustances ou p. 175 of the visibility of Jupiter's 

 Siitellitos with the nuked eve. 



I should like to know if Mr. Maunder concurs with Mr. 

 AVobb or uot. 



I can just make out Venus' crescent mjself witli a 

 binocular of Browninii's; diameter of object glass, 1* incii, 

 focal length. 8 to inches. 



Apropos of Mr. C. Jackson's note on p. 81, I recollect 

 that in July, 1873, being then at St. Leonards on a visit, 

 and having, of course, a good horizon, 1 just managed to 

 see the dark spaces between the rings and body of Saturn, 

 with a small pocket glass by E<.>ss ; object glass 1| to 1| 

 inches, and 2'>ower of about 29, a very similar glass to that 

 referred to on p. 2, Vol. I. of Webb. 



Pawston, Cornhill-on-Tweed, B. P. Selbt. 



April 15th, 1902. 



[I fear that I cannot add anything to what 1 have 

 already written as to the crescent of Venus being visible 

 to the naked eye, viz., that I think it " outside the limit of 

 possibility." If it has ever been achieved, then certainly 

 the observer must have been possessed of most exceptional 

 powers of sight. The case of Theodore Parker, quoted by 

 the Eev. T. W. Webb, inay be a real one, as children 

 sometimes show an acuteness of vision which is not 

 retained in mature life : but I should personally feel no 

 confidence in any statement of the kind that I had not 

 been able to subject to a rigorous testing. I have 

 rejieatedh' tried to make the observation myself at a time 

 when my eyesight was distinctly above the average in 

 quality. Thus I could at one time couut eleven stars in 

 the Pleiades, I have distinctly identified both Uranus and 

 Vesta when in opposition and high in declination, I could 

 clearly separate Ej and b^ Lyrse, and I have veiy often seen 

 Venus at mid-day. But I never could make the slightest 

 approach to defining the crescent of Venus, and the optical 

 assistance necessary to do it has always been considerable. 

 The increase of power which is given by such a binocular 

 as Mr. Selby used is very marked indeed, and I am 

 sceptical as to anyone possessing sight in advance of his 

 fellows to an extent comi^arable with it. I may have done 

 the American Stoddart an injustice, but I always 

 regarded his claim to have seen the crescent of Venus and 

 to have elongated Saturn with the naked eye as " requiring 

 confirmation." 



The case of the satellites of Jupiter is quite diii'erent. 

 I see no reason why III. should not be seen at elongation 

 when the planet is high ; nor IV. either, though its 

 comparative faiutness will render it a severer test of good 

 sight. Under very exceptional circumstances, II. may be 

 elongated almost four minutes of arc and might then be 

 detected under favourable conditions of weather and 

 altitude of the planet. But I should like to receive very 

 full confirmation of any alleged observation of I. There is 

 no reason to call in question observations where two of the 

 satellites have been close together and have been seen as 

 one, if the distance from their primary was considerable 

 at the time. 



I shall feel much gratified if my paper induces many 

 observers to seriously take up the question of these obser- 

 vations, which are so nearly on the limit of visibility, and 

 which form such searching tests of goodness of sight. — 

 E. Waltek Maundee.] 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — During the recent easterly elongation of Venus, 

 I was one evening watching the planet through Mr. 

 Fowler's " Telescopic Astronomy " telescope. A friend, 

 ignorant of astronomy, and of the fact that astronomical 



(elenropes give inverted imagee, called, and was shown 

 Venus through the instrument. To find out if he really 

 was seeing what he was supposed to see, I asked him the 

 shaj)e of the j)lanet — did it seem round ? He answered: 

 " No, it is crescent-shaped as it was last night, but the 

 crescent is turned the other way." He had, it turned out, 

 been watching Venus the night before with the naked eye. 



The incident convinced me that Venus can be seen as a 

 crescent by the naked eye of at least one man, and is, 

 perhaps, worth repeating in view of Mr. Maunder's 

 remarks on page 79 of the April number. 



Schoolhouse, James Eodger. 



Eattray, Blairgowrie, 



3rd April, 1902. 



93v(ttstj C^vnitljologtcal Xotts. 



Conducted by W. P. Pyceaft, a.l.s., f.z.s., m.b.o.u. 



Spoonbills in Norfolk. — Mr. ,J. H. Gurney, in the 

 Zoologist for March, gives an exceedingly interesting 

 account of a small flock of Spoonbills which frequented 

 Breydon Water, Great Yarmouth, from early April to the 

 end of July, 1901. Thanks to the efforts of the Breydon 

 Wild Birds Pi'otection Society, none of these appear to 

 have fallen victims to the crowd of gunners who haunted 

 the spot in the hope of securing specimens. It is to be 

 hoped that, in the near future, these birds may be induced 

 once again to nest in their old haunts — the heronry of 

 Eeedham, close by. Unless, however, the society receives 

 more liberal support from those interested in the restoration 

 of this and other some-time resident species, the society, 

 we note with regret, will be unable to continue its good 

 work ; in which case all hope of restoring the Spoonbill 

 to its ancient stronghold must be abandoned. 



We have to record, with regret, that a nearly adult female 

 Spoonbill was purchased at Harrod's Stores, London, 

 during Holy Week of the present year (1902), by one of 

 the taxidermists of the Natural History Museum, Crom- 

 well Eoad. The bird was in good condition, and perfectly 

 fresh. Careful inquiries show that the bird came from 

 Leadenhall Market, and was said to have come up with a 

 consignment of birds from Great Yarmouth. 



PoLLiNATiox BY BiEDS.— Au exti'cmely interesting 

 exhibition of photographs was "given at the meeting of the 

 Linuean Society on March 6th. illustrating certain New 

 Zealand plants which depend for fertilization upon certain 

 species of birds. The New Zealand bell-bird (Anthornis 

 melanura) is one of these fertilizers; performing this 

 office for the native fuchsias and the native flax. In the 

 course of its visitations the bird's head becomes thickly 

 covered with pollen, so that, at different times of the year, 

 according which of these two plants is in flower, the bell- 

 bird may be obtained either with a liright IjIuc or a red 

 forehead; these colours being due to the pollen. Some 

 years ago this led to a curious mistake, Von Pelzen describing 

 one of the red-headed birds as a new species — Anthornis 

 rnficeps. Athough at the time many doubted the validity 

 of" this, it was not till 1870 that the supposed new species 

 was abandoned, proof having been given of the artificial 

 nature of the red coloration. 



Birds and the Production of Pearls. — At the 

 meeting of the Zoological Society held ou March 4th, Dr. 

 Lvster Jameson read a paper on the "Origin of Pearls in 

 the Common Mussel (Mytihis cdulis)." He showed that 

 the ])earls commonly found in these molluscs were due to 

 the presence of a parasitic Distomid larva, which, pene- 

 tratiu"- the mantle of the mussel, became encysted. On tlie 



