174 



NA TURE 



[June 23, 1887 



J. M. H. — viz. the emjiloyment by some finches of flowers 

 in the formation of their nests (Nature, vol. xvi. p. 83, and 

 vol. xxxvi. pp. 101-2) — it may be worth while to sub.nit a 

 detailed consideration of the case. 



The front of the house of a friend living at No 47 Highbury 

 Hill is covered by an extensive growth of white jasmine which 

 reaches beyond the first-floor windows. For several years 

 house sparrows have used the bushy branches of this shrub 

 without causing special attention. This year, however, they 

 have taken a new departure in nest-building. Not satisfied, 

 apparently, with the hay, straw, and other ordinary materials of 

 sparrow architecture, they have suddenly aspired to appropriating 

 to their use the briglit yellow flowers of laburnum, two trees of 

 which are in full bloom a few yards from the first-floor window- 

 sills below which they are carrying on their operations. Three 

 nests were discovered twelve days ago, built close together in 

 the jasmine, all of which had laburnum fl jwers strewn upon the 

 top of ordinary nests ; one nest contained two young birds just 

 hatched, and the o'.her two had each a couple of eggs. As 

 they rather disturbed the lady occupant of the house, she had 

 all three nests destroyed, the litter from them entirely filling a 

 large foot-bath. Bat the three pairs of birds, as might be 

 expected, only set to work rebuilding their nests in the same 

 place, furnishing them with more laburnum than befjre. They 

 were however again disturbed, and an ob tacle (which in a 

 previous year hid proved effectual in stopping the building in 

 another part of the house front) was set in the place of the 

 nests, but still they did not desist ; two pairs continued to add 

 their materials on the top of it, with more laburnum than ever, 

 replenishing the nest as constantly as it was removed, while tha 

 third pair rebuilt their nest under the siil of the next window, 

 using laburnum also. Even entire sprays of the flowers were 

 used, and the ground beneath the trees was so much strewn with 

 fragments that my friend at first thought that boys had been 

 pulling the trees. All the birds are now allowed to remain un- 

 molested, and the yellow decoration is withered, without fresh 

 being provided. 



This unaccusto:r.ed action of the sparrows is apparently 

 somewhat different from the operations described by your corre- 

 spondent J. M. H., for the bright golden flowers enveloping 

 the nests are so strangely conspicuous as to attract the attention 

 of passers-by, and therefore cannit answer the protective 

 purpose evident both in the case of the goldfinches with forget- 

 me-nots and of the sparrows that used Alyssum. The only 

 explanation I can suggest is that the birds have tlevated their 

 aesthetic taste to this " quite too too " extent of art cultus. It is 

 highly interesting to note also that — in opposition to the notions 

 of the obsolete school of naturalists, who believed on!y in blind 

 instinct — the rage for collecting their favourite "yellow" is 

 infectious with these little yearners for the intense, just as is the 

 desire for " blue" that now and then breaks out (like a disease) 

 amongst larger householders. The three pairs of birds seemed 

 to vie with one another in their revelry of the chosen colour. 

 It will be instructive to learn whether the fashion wdll last for 

 many seasons : perhaps it will languish of satiety, and some 

 other attraction of a less absorbing kind arise. 



The fondness of birds (in this country at least), for the colour 

 yellow is perhaps worth considering in this connexion. A 

 large number of wild or cult vated plants might be enumerated 

 that produce yellow flowers, which are either used as food 

 or have their petals mauled by birds. There need be no doubt, 

 I think, that the mutilation of such flowers is due to a playful 

 fondness rather than to a dislike of the flowers. That birds 

 evidently exercise the selective faculty in the choice of flowers 

 is well illustrated by the fact, twice observed by my brother, 

 that sparrows pull to pieces the yellow flowers only in mixed 

 beds of pansies, and of crocuses, without injuring a single 

 purple, mauve, or wdiite flower of either kind. I have myself 

 also witnessed the same selective operation performed by a 

 sparrow on various crocuses growing in jDOts upon my window- 

 sill, and I find many correspondents gave, similar tes'imony 

 to this fact in a series of letters which appeared in these pages 

 in the year 1877 (vols. xvi. and xvii. ). It may be questioned 

 whether the education of their preference for the colour yellow 

 is in any way connected with the fact that it is proper to the 

 yolk of their eggs, and which they must be aware of ; but since 

 all good eggs contain that colour, while probably some birds 

 do not like it and greatly prefer other colours, this suggestion 

 may be no more valid as a theory than would be the argument 

 that some people's taste for cliret- colour is due to the anal:)gous 



physiological accident of arterial coloration. The rich yellow 

 colour, again, of the beaks, entire mouths, and "open sepulchres" 

 of the newly-hatched nestlings affords their parents ample oppor- 

 tunities for the contemplation of colour, and there may be an 

 unconscious mental absorption of the colour in consequence of 

 this course of training. At any rate, canary yellow is very highly 

 developed in many species of the Fringillida:, and there is a 

 strong tendency towards the development of the yellowish colour 

 in the plumage of the males of several British finches, apparently 

 through a greenish-brown tinge. It is also well developed 

 amongst the weavers and the orioles, to which they are so nearly 

 allied. That sparrows should thus iise sprays of flowers is 

 perhaps not so remarkable when we recall the close affinity they 

 bear to Ploceiis and other weaver-birds. 



Doubtless the colour-sense in birds, as well as in insects, is a 

 real factor in the evolution of the flo-al beauty that surrounds 

 them, although the modus operandi is not always one that can be 

 so readily traced. William White. 



55 Highbury Hill, London, June 9. 



Names for Electric Units of Self-induction and 

 Conductivity. 



A NA.ME seems to be wanted for the practical unit of self- 

 induction, viz. an ohm multiplied by a second ; in other words, 

 for a length approximately equal to an earth- quadrant. Profs. 

 Ayrton and Terry call it a "secohm." Why not call it a 

 "quad"? It would be a handy great length for many other 

 purposes. For instance, the velocity of light in air would be 

 30 quads per second, in common glass 20 quads per second. 



To avoid misunderstanding, it would have to be understood 

 that the actual earth-quadrant passing through any given place is 

 only approximately a quad, its real value having to be determined 

 geodetically. A quad is to be understood as ten million metres 

 precisely. 



Another unit requiring a name is the unit of conductivity. Sir 

 William Thomson has suggested the word " mho," but it has not 

 been greedily assimilated. I make the small suggestion of 

 omitting the h. True, the expressions 12 mo and i6 mo would 

 at first excite only bookbinding ideas, but they would soon 

 carry a fresh meaning to electricians. Oliver J. Lodge. 



June 13. 



Units of Weight, Mass, and Force. 



The necessity for names for the units of velocity and accelera- 

 tion is very clearly illustrated by a criticism of my " Dynamics 

 for Beginners," which appears in the Practical Engineer of 

 June 3. After objecting to the introduction of new names, and 

 explaining that a velo stands for a foot per second, the writer 

 proceeds: — "The second new name is 'celo,' and is meant 

 for an acceleration of one foot per second, or unit accelera- 

 tion ; so that if a body is moving with a velocity which is 

 being accelerated at the rate of one foot per second, it is 

 said in the new language to possess one celo. In other words, a 

 celo means an acceleration of one foot per second, or of one velo." 

 The italics are mine. I cannot resist quoting also the following 

 sentence, which occurs a little lower down in the same criticism : 

 — " We think there is something ridindous about the adoption 

 of these names, which, while possessing the very questionable 

 advantage of shortening the language of the subject by some two 

 or three words, se7-ve to tnuddle the mind of the student, and to 

 obscure the sense by wrapping it up in meaningless zuords. " 



Why is not the Practical Engineer consistent ? He ought to 

 state that just as a celo is unnecessary, for he considers it the 

 same as a velo, in like manner a velo is unnecessary, for by the 

 same line o.*" argument it must be the same as afoot. The fact 

 is that the names velo and celo are not necessary for scientific 

 men, although I expect they will be found to* be convenient. It 

 is, I believe, generally admitted that some such words are 

 greatly needed by teachers ; for it is the clear mental differentia- 

 tion of the ideas expressed by velo and celo, or the want of it, 

 which often marks the distinction between a sound physicist and 

 a muddler. John B. Lock. 



Gonville and Caius College, June 4. 



I AGREE with your correspondent, Mr. R. B. Hayward 

 (Nature, vol. xxxv. p. 604), in holding that names for the 

 dynamxal units are of less importance than a convenient nota- 



