March, 1913. 



KNOWLEDGE. 



105 



to stimulate the optic nerve, the picture is lost altogether. 

 The failure to define, however, by the glass of 0-50 N.A., 

 which is so well shown by the N.A. of 0-85, is not all due to 

 the want of resolving power in the former. Could the little 

 bosses be isolated from the cross ribs they would be seen by 

 the smaller N.A. readily enough. But here, with the larger 

 aperture of the one-sixth inch comes in another valuable 

 quality, seemingly not appreciated by Mr. Hutton. It does 

 not consist of the depth of focus he speaks of. Rather this is 

 its opposite, allowing two structures, one superimposed upon 

 the other, and but a little apart, to be separated optically. In 

 the words of Dr. Abbe, a wide aperture then becomes an 

 optical microtome. In conclusion, I have not met all his 

 points, but have already written enough, I think, to give a 

 good opening for the discussion which I hope 



wi " follow - T. F. Smith. 



THE ROYAL MICROSCOPICAL 

 SOCIETY. — At the meeting held on February 

 19th, the new President, Professor Sims 

 Woodhead, took the chair for the first time. 

 Mr. E. J. Spitta gave a very interesting 

 account of the lenses formerly belonging to 

 Joseph Lister, which had been presented to 

 the Society by the Executors of his son, the 

 late Lord Lister. Many of the lenses were of 

 great historical interest. Some of them had 

 been made by Joseph Lister himself, others 

 appeared to be the first examples produced by 

 well-known makers. Among the manuscripts 

 which accompanied the apparatus was a 

 paper which, so far as Mr. Spitta had been 

 able to determine, had never been published, 

 in which Joseph Lister, had in a marvellous 

 way anticipated the work of Abbe carried out 

 forty or fifty years later. A remarkable 

 feature of the lenses made by Lister himself 

 was the high polish which had been given to 

 them. This is more to be wondered at seeing 

 the methods which had to be adopted. 



Mr. C. Lees Curties exhibited, on behalf of Mr. H. 

 Waddington, a striking series of slides illustrating the 

 development of the Fairy Shrimp (Chirocepliahis dia- 

 phantis). These included the egg and several examples of 

 the nauplius in various stages, as well as the young shrimps 

 and preparations illustrating parts of the full-grown animal. 

 Dr. Shillington Scales read the notes which were sent with 

 the slides, from which it appeared that the crustacean while 

 of only occasional occurrence in England generally, was not 

 uncommon in parts of Cornwall. To the list of localities 

 mentioned, Mr. Wilfred Mark Webb added Eton, Mr. D. J. 

 Scourfield one near Oxshott, while Mr. John Hopkinson 

 mentioned a record for Hertfordshire. 



Mr. D. J. Scourfield described the use of the centrifuge in 

 pond-life work, pointing out that organisms could be obtained 

 from water that was apparently free from them by the use of 

 this apparatus. He said that in the past it had been taken 

 up rather as a substitute for fine nets, but it should be looked 

 upon as supplementing them. 



Another feature which contributed towards making a most 

 attractive meeting, was the exhibition of Desmids by members 

 of the biological section of the Royal Microscopical Society. 



TAKING CINEMATOGRAPH PICTURES WITH THE 

 MICROSCOPE. — We have received a very useful booklet 

 entitled " Guide to Photo-micrography." It is published by 

 Mr. E. Leitz, and it was primarily prepared for users of 

 apparatus supplied by him. In the first place we are told 

 how to set this up, and to make photographs with the camera 

 put vertically and horizontally. Special apparatus for photo- 

 graphing insects, large sections, and solid objects, is illustrated 

 and described. The photographic side of the work is dealt 

 with as is also the making of cinematograph pictures. 

 Altogether the Guide is a very valuable help to those who 

 wish to take up photo-micrography in connection with their 

 work or as an attractive hobby. 



By 



ORNITHOLOGY. 



Wilfred Mark Webb, F.L.S. 



A SWALLOW RINGED IN STAFFORDSHIRE AND 

 RECOVERED IN NATAL.— On May 6th, 8911, Mr. 

 J. R. B. Masefield ringed two swallows (Chelidon rustica) 

 which were nesting in the porch of his house, Rosehill, 

 Cheadle, Staffordshire. In the summer of 1912 he again 

 caught the swallows nesting in the porch but found that only 

 one of them bore the ring which he had put on in the previous 

 year. On December 23rd, 1912, a swallow was caught in a 

 farmhouse eighteen miles from Utrecht in Natal, and this 

 proved to be the bird which did not return to Cheadle in that 

 year. Mr. Harry Witherby, who records the occurrence in 

 British Birds for February, thinks it extra- 

 ordinary that a swallow breeding in the far 

 west of Europe should have reached the 

 south-east of Africa. He finds it is quite 

 impossible to theorise on a single recovery 

 of this kind but tells us that we must be 

 content at present with the bare fact, probably 

 the most startling one that the ringing of 

 birds has as yet produced. 



Figure 100. 



A New Nesting Box for 

 Nature Study Observations. 



NESTING BOX EXHIBITION.— A very 

 successful exhibition of nesting boxes, held 

 during the first fortnight of February in the 

 offices of the Selborne Society, was organ- 

 ised by the Brent Valley Bird Sanctuary Com- 

 mittee. The nesting boxes which, when they 

 were first designed, were described and illus- 

 trated in "Knowledge" (Volume XXXIV, 

 page 99), have now reached a stage at which 

 they are not capable of very much more im- 

 provement, for they have been modified in the 

 light of experience and the less successful 

 forms have been dropped. There was nothing, 

 therefore, very novel to be seen, though one 

 box was interesting. Instead of being made 

 from a small log, it is cut from half a tree 

 trunk (see Figure 100). This gives it a flat back, and it is 

 very suitable for hanging on a wall, amongst ivy, for 

 instance. The top lifts off for observational purposes, and 

 instead of being fixed by nails driven through metal plates 

 the box can be hung on a single hook. It is specially intended 

 for nature study observations, and for use in school gardens 

 and playgrounds, for it can be put up out of reach and 

 taken down for examination by the teacher quite easily 

 when required. As was seen at the Children's Welfare 

 Exhibition, country children are able to make very excellent 

 observations on birds which build in the open, and the use of 

 nesting boxes gives them, as well as their town and suburban 

 cousins, a chance of studying the nesting habits of 

 those birds which customarily rear their young in holes. 

 Another contrivance worthy of mention is an experi- 

 mental box, made, with the idea of attracting tree-creepers, 

 from a slice of a curved branch, the object being when 

 it is attached to a tree to make it appear as if it were 

 part of the actual trunk. 



THE LATE STAY OF SWIFTS.— Mr. H. B. Booth, in 

 The Irish N atiiralist for February, criticises the expression 

 used in previous notes on the Swift — " despite the coldness 

 of August, and the summer, the Swifts did not depart." He 

 says that the writers should have said because of the cold 

 August and Summer, for his observations go to show that 

 with the members of this species the date of their departure 

 is fixed more by the forwardness of their young brood, and 

 their ability to undertake the long journey, than by the state 

 of the weather, or of their food supply at the time of leaving. 

 As a matter of fact, in the finest summers and consequently 

 when there is a large supply of winged insect food, the colony 

 usually breaks up a day or two earlier than in colder and 

 wetter seasons. It must be obvious that in the former case 

 the young ones would be better fed, and come to maturity 

 earlier. 



