88 



KNOWLEDGE 



[Mat 1, 1898. 



perhaps, be called the heel of the foot, upon which it 

 throws most of its weight, just as the woodpecker throws 

 its weight on the tail, when in a similar posture. When 

 pecking very hard, the bird bends its head right back, and, 

 as it strikes the tree, gives a flap with its wings in order 

 to preserve its balance. If the bird cannot easily dislodge 

 a piece of bark at which it is pecking, it will walk all round 

 it, tapping it with its beak at every possible point, until 

 the object is attained. The beak being broader than high 

 at the base, and very hard, is well suited to give a strong 

 blow. 



The nesting habits of this bird are peculiar. It builds 

 in a natural hole in a tree, not boring a hole for itself 

 like the woodpeckers ; but if the entrance to the cavity 

 should be too large, or if there be any unevenness in 

 it, the bird will plaster it 

 round with mud to make 

 the hole the required size, 

 and it never seems to be 

 satisfied until the hole is 

 exactly round, and only 

 just large enough for it to 

 enter. 



If the mud be examined, 

 the marks of the bird's 

 beak in the form of minute 

 holes are seen all over it, 

 showing with what care the 

 work has been done. 



In some parts of the 

 country, in the New Forest 

 for instance, the nuthatch 

 is caUedthe "mud-dabber," 

 from this singular habit of 

 " dabbing " mud round the 

 entrance to its nest. 



Nuthatches very often 

 fight with tits of various 

 kinds for the possession of 

 a favourite hole for nesting 

 purposes ; and this may be 

 the reason for its habit of 

 making the entrance as 

 small as possible, as a 

 larger aperture would be 

 less easily defended. 



The nest itself is com- 

 posed of moss and leaves, 

 and very often chips of 

 wood are introduced ; 

 one which I examined 

 was entirely composed 

 of small flakes of bark 

 from a yew tree. These 

 materials are all broken up 

 into very small fragments, so 

 if they had been cut in pieces 

 They are carried into the hole 

 any order, and no attempt is 

 together. Upon this 



are usually five to seven in number. They are white, 

 spotted over with reddish-brown, and can scarcely be 

 distinguished from the eggs of the cole tit {Piiru.i atrr). 



The eggs are usually laid in the middle of May. During 

 the process of incubation, which lasts some fourteen days, 

 the bird sits very close, and may be even looked at without 

 causing her to leave the nest. A hole quite close to the 

 road is very often chosen for the nest, and I have known 

 one that was situated just over a seat that was in constant 

 use. The bird hides the eggs in the nest before leaving it. 



The nuthatch is not a good musician. It has no regular 

 song, but utters several different call notes, the chief of 

 which is very shrill and piercing, and when once heard 

 will not easily be forgotten. It sounds like the syllable 

 " twhit " repeated very quickly, usually four or six 

 times in succession. It has also a note sounding like 

 " twe-twhit," the last syllable being longer than the first, 

 which is very short. Another note, not so often used, 

 resembles the syllable " tyrrh,"' repeated quickly twice, and 

 then a third time prolonged. 



The flight of the nuthatch is undulating, but very rapid. 



ULttXtt^. 



[The Editor does not hold himself responsible for the opinions 

 statements of correspondents.] 



THE y) 

 To 



Xutliatilifs and Nest, >liuuii 



that the leaves look as 

 with a pair of scissors, 

 apparently without 

 made to weave them 

 nest the bird lays her eggs, which 



ARGtJS NEBULA. 



the Editor of 

 Knowledge. 



Deae Sir, — In the very 

 interesting paper compar- 

 ing Sir John Herschel's 

 drawing with Dr. Gill's 

 photograph, in mentioning 

 the trident-shaped struc- 

 ture, it says : " There 

 seems to be no nebulosity 

 corresponding with it in 

 position on the photo- 

 graph." 



Is there not a faint nebu- 

 losity, corresponding to the 

 drawing shown in the pho- 

 tograph, in row 10, columns 

 22 and 28, and lower part 

 of row 1 1 , column 23 ? 



There appears to me a 

 curve, as it were the 

 "Swan's" head, with a star 

 on either side of the line, 

 between rows 10 and 11 in 

 column 23, very similar to 

 Sir John Herschel's draw- 

 ing. 



Yours truly, 



Vincent Yakdley. 

 " Kavenscroft," 



Church Hill, 

 Iloddesdon, Herts. 

 April 19th, 1893. 



[Mr. Yardley is, I think, 

 correct, but if we assume 

 i-iitraiitc ]iliistorcd with mud. that the structure he 



refers to was the one seen and drawn by Sir John 

 Herschel, we must make one of three assumptions — either 

 there has been a great change in the relative bright- 

 ness of various parts of the nebula since 1887 ; or Sir 

 John Herschel must have made serious errors in estimating 

 or in representing the relative brightness of different parts 

 of the nebula, and he must have seen with his great 

 Herschelian reflector parts of the nebula which now, by 

 reason of their faintness, are only just traceable in Dr. 

 Gill's photograph, taken with an exposure of over twelve 

 hours ; or the brightness of this structure as seen with 

 the eye must be greater than as shown in the photograph — 

 for example, its light might be redder than that of the 

 rest of the nebula. 



By a careless mistake I referred to Herschel's great 



