Jan. 6, 1887] 



NA TURE 



237 



the dipper, which breed in holes, are not gorgeously coloured, 

 while others, such as tlie pheasants and the humming-birds, are 

 gorgeously coloured, but do not breed in holes, is evidence, as 

 far as it goes, that the gorgeous colour of the bird is not the 

 c-ll'ect of its breeding in a hole, though the white colour of the 

 I'gg probably is. It must be admitted, however, that the latter 

 cases are not parallel. Whilst the hen kingfishers and bee- 

 eaters are as gorgeous as their mates, the hen pheasants and the 

 hen humming-birds are plainly, not to say shabbily, dressed. 

 If birds be as vain as the advocates of sexual selection deem them, 

 it must be a source of deep mortificttion to a hen humming-bird 

 to have to pass through life as a foil to her rainbow-hued mate. 

 Whilst the kingfisher relies for the safety of its eggs upon the 

 concealed situation of its nest, the humming-bird depends upon 

 the unobtrusiveness of the plumage of the sitting hen. 



A very large muiiber of birds, such as the grouse, the merlin, 

 most gulls and terns, and all sandpipers and plovers rely for the 

 safety of their eggs upon the similarity of their colour to the 

 ground on which they are placed. It may be an open question 

 whether these birds select a site for their breeding-ground to 

 match the colour of the eggs, or whether they have gradually 

 changed the colour of their eggs to match the ground on which 

 they breed ; but, in the absence of any evidence to the contrary, 

 it is perhaps fair to assume, as in the previously mentioned cases, 

 that the position of the nest is the cause, and the colour of the 

 egg the effect. 



Many birds make their nests in lofty trees, or on the ledges of 

 precipitous cliffs. Of these, the eagles, vultures, and crows are 

 conspicuous examples. They are, fur the most; part, too power- 

 ful to be afraid of the marauding magpie, and only fear the 

 attacks of beasts of prey, amongst which they doubtless classify 

 the human race. They rely for the safety of their eggs on the 

 inaccessible positions of the nest. Many of them also belong to 

 a still larger group of birds who rely for the safety of their eggs 

 upon their own ability, either singly, in pairs, or in colonies, to 

 defend them against all aggressors. Few colonies of birds are 

 more interesting than those of herons, cormorants, and their 

 respective allies. These birds lay white or nearly white eggs. 

 Nature, with her customary thrift, has lavished no colour upon 

 them because, apparently, it would have been wasted effort to 

 do so ; but the eggs of the guillemot are a remarkable exception 

 to this rule. Few eggs are more gorgeously coloured, and no 

 eggs exhibit such a variety of colour. It is impossible to sup- 

 pose that protective selection can have produced colours so 

 conspicuous on the white ledges of the chalk cliffs ; and sexual 

 selection must have been equally powerless. It would be too 

 ludicrous a suggestion to suppose that a cock guillemot fell in love 

 with a plain-coloured hen because he remembered that last 

 season she laid a gay-coloured egg. It cannot be accident that 

 causes the guillemot's eggs to be so handsome and so varied. 

 In the case of birds breeding in holes secure from the prying 

 eyes of the marauding magpie, no colour is wasted where it is 

 not wanted. 



The more deeply Nature is studied, the more certain seems to 

 be the conclusion that all her endless variety is the result of 

 evolution. It seems also to be more and more certain that 

 natural selection is not the cause of evolution, but only its guide. 

 Variation is the cause of evolution, but the cause of variation is 

 ttnknown. It seems to be a mistake to call variation spon- 

 taneous, fortuitous, or accidental, than which expressions no 

 adjectives less accurate or more misleading could be found. The 

 Athenian philosophers displayed a less unscientific attitude of 

 mind towards the Unknown when they built an altar in its 

 honour. 



SCIENTIFIC SERIALS 



American Journal of Science, December i886. — On the 

 crystallisation of native copper, by Edward S. Dana. This 

 elaborate memoir, which is illustrated with four plates figuring 

 fifty-four varieties of native copper crystalline forms, is based 

 chiefly on the fine collection of over sixty specimens from Lake 

 Superior, belonging to Mr. Clarence S. Bement, of Philadel- 

 phia, supplemented by reference to the cabinets of Vale College 

 Museum and Trof. G. J. Brush. The planes here determined are 

 disposed in the three groups of tetrahexahedrons, trisoctahedrons, 

 and hexoctahedrons, and include several new to the species. 

 The paper also comprises an historical summary from the studies 

 of Hauy and Mohs (1822) to the recent contributions of W. G. 



Brown. — On the trap and sandstone in the gorge of the Farm- 

 ington River at Tariffville, Connecticut, by W. North Rice. The 

 trap and sandstone of this locality are here specially studied with a 

 view to the general elucidation of the history of these formations in 

 the Connecticut Valley. The author's researches confirm the con- 

 clusion already arrived at by Prof. W. M. Davis, that some of 

 the sheets of trap intercalated among the sandstones and asso- 

 ciated rocks are contemporaneous, and others intrusive. — Com- 

 parative studies upon the glaciation of North America, Great 

 Britain, and Ireland, by Prof. H. Carvill Lewis. This is an 

 abstract of a paper by the author, read at the Birmingham meet- 

 ing of the British Association last September. Its object is to 

 show that the glacial deposits of the British Isles, like those 

 of America, may be best interpreted by considering them with 

 reference to a series of great terminal moraines, which both 

 define confluent lobes of ice, and often mark the line 

 separating the glaciated from the non-glaciated areas. — On 

 certain fossiliferous limestones of Columbia County, New 

 York, and their relation to the Hudson River shales and the 

 Taconic system, by J. P. Bishop. The author describes some 

 new fossils recently discovered in a metamorphic limestone occur- 

 ring in the Chatham and Ghent districts on the western border 

 of tlie Taconic slates of Columbia county, and tending to throw 

 further light on the age of the Taconic formation. His investi- 

 gations are still in progress, but from the facts so far deter- 

 mined, he considers that the fossils are of Trenton age, 

 suggesting a synclinal having the Trenton limestone outcropping 

 on both sides, and with the eastern edge pushed over westward. 

 — Crystallised vanadinite from Arizona and New Mexico, by 

 S. L. Penfield. The specimens here described and figured 

 belong partly to the collection of the late Prof. B. Silliman, 

 partly to that of Prof. Geo. J. Brush. Those from Pinal County, 

 Arizona, are specially interesting, being of a deep red colour, 

 and usually showing the very simple combinations already de- 

 scribed by L. H. Blake. — The viscosity of steel and its relations 

 to temper, by C. Barus and V. Strouhal. Having during the 

 course of their former researches expressed the belief that the 

 qualities of retaining magnetism exhibited by steel would pro- 

 bably stand in relation to the viscous properties of the metals, 

 the authors here make a first search for such a relation. For 

 several reasons their investigations are limited to torsional vis- 

 cosity, and a new and very sensitive differential method is par- 

 tially developed for the study of this property, with incidental 

 reference to the viscosity of iron and glass. The results of the 

 method as applied to steel are further compared with the 

 known behaviour of permanent linear magnets tempered under 

 like conditions. — Some remarks upon the journey of Andre 

 Michaux to the high mountains of Carolina in December 1788, 

 in a letter addressed to Prof. Asa Gray, by C. S. Sargent. 

 Michaux's chief object was to secure living specimens of Mag- 

 nolia cordata, and the locality explored by him appears to have 

 been the highland region of North and South Carolina about the 

 head waters of the Savannah River. The author has recently 

 visited the same district for the purpose of re-discovering the 

 same plant where Michaux was thought to have found it, but he 

 searched for it in vain, and he concludes that Michaux's Mag- 

 nolia cordata, as known in gardens, must be regarded as a rare 

 and local variety of M. acuminata. — Note on the age of the 

 Swedish Paradoxides beds, by S. W. Ford. It is argued on 

 several grounds that these beds, or at any rate those above the 

 division characterised by Paradoxides kjerulfi, are of the age of 

 the Menevian group. Even this species should probably be 

 referred to the same group, so that the strata containinj it may 

 be regarded as constituting a legitimate portion of the Swedish 

 Paradoxides measures. 



Rivista Scientifico-Industriale, November 1886. — On the de- 

 velopment of atmospheric electricity which accompanies the 

 condensation of aqueous vapour to rain or snow caused by a 

 lowering of the temperature, by Prof. Luigi Palmieri. Those 

 physicists who still doubt the reality of this phenomenon are re- 

 commended to conduct their re^earches with the Bohnenberger 

 electroscope, as perfected by the author. — On the electric con- 

 ductibility of vapours and gases, by Prof. Constantino Rovelli. 

 Some experiments are described, fully confirming the important 

 conclusions recently announced by Prof. Luvini regarding the 

 non-conducting property of aqueous vapour. — On the pairing- 

 season of frogs and toads in the Venetian district, by Dr. Ales- 

 sandro P. Ninni. This period is shown to be determined by the 

 atmospheric conditions, being advanced or retarded according 

 to the mildness or severity of the weather in spring. 



