57 



THE POPULAR SCIENCE MONTHLY. 



supplies in the winter quarters. The north- 

 ward movement of all the others must be 

 through some impulse not yet ascertained. 

 In many other instances it is not dependent 

 on the weather at the moment. This is es- 

 pecially the case with sea birds. Prof. New- 

 ton observes they can be trusted as the 

 almanac itself. Foul weather or fair, heat 

 or cold, the puffins Fratercula arctica re- 

 pair to some of their stations punctually on 

 a given day, as if their movements were 

 regulated by clockwork. In like manner, 

 whether the summer be cold or hot, the 

 swifts leave their summer home in England 

 about the first week in August only occa- 

 sional stragglers ever being seen after that 

 date. To say that migration is performed 

 by instinct is no explanation of the marvel- 

 velous faculty ; it is an evasion of the dif- 

 ficulty. The sense of sight can not guide 

 birds which travel by night, or span oceans 

 or continents in a single flight. In noticing 

 all the phenomena of migration there yet 

 remains a vast untilled region for the field 

 naturalist. What Prof. Newton terms the 

 sense of direction, unconsciously exercised, is 

 the nearest approach yet made to & solution 

 of the problem. He remarks how vastly 

 the sense of direction varies in human be- 

 ings, contrasting its absence in the dwellers 

 in towns compared with the power of the 

 shepherd and the countryman, and, infi- 

 nitely more, with the power of the savage or 

 the Arab. 



Chemical Constitution and Color. A 



curious side light, says Prof. James Emerson 

 Reynolds, seems to be thrown on the nature 

 of the elements by the chemico-physical dis- 

 cussion of the connection existing between 

 the constitution of certain organic com- 

 pounds and the colors they exhibit. We 

 may take it as an established fact that a 

 relation exists between the power which a 

 dissolved chemical compound possesses of 

 producing the color impression within our 

 comparatively small visual range, and the 

 particular mode of grouping of its constitu- 

 ent radicals in its molecule. Further, the re- 

 ality of this connection will be most freely ad- 

 mitted in the class of aromatic compounds 

 that is, in derivatives of benzene, whose con- 

 stituents are so closely linked together as to 

 exhibit ^Masz-elemental persistence. If, then, 



the possession of what we call color by a 

 compound be connected with its constitution, 

 may we not infer that " elements " which 

 exhibit distinct color, such as gold. and cop- 

 per, in thin layers and in their soluble com- 

 pounds, are at least complexes analogous to 

 definitely decomposable substances ? This 

 inference, while legitimate as it stands, would 

 obviously acquire strength if we could show 

 that anything like isomerism exists among 

 the elements ; for identity of atomic weight 

 of any two chemically distinct elements 

 must, by all analogy with compounds, imply 

 dissimilarity in constitution, and therefore 

 definite structure, independently of any ar- 

 gument derived from color. Now, nickel 

 and cobalt are perfectly distinct element?, 

 as we all know, but, so far as existing evi- 

 dence goes, the observed differences in their 

 atomic weights (nickel, 68'6 ; cobalt, 58'7) 

 are so small as to be within the range of the 

 experimental errors to which the determina- 

 tions were liable. Here, then, we seem to 

 have the required example of something like 

 isomerism among elements, and consequently 

 some evidence that these substances are 

 complexes of different orders ; but in the 

 cases of cobalt and nickel we also know that 

 in transparent solutions of their salts, if not 

 in thin layers of the metals themselves, they 

 exhibit strong and distinct colors compare 

 the beautiful rosy tint of cobalt sulphate 

 with the brilliant green of the corresponding 

 salt of nickel. Therefore, in exhibiting 

 characteristically different colors, these sub- 

 stances afford us some further evidence of 

 structural differences between the matter of 

 which they consist, and support the conclu- 

 sion to which their apparent identity in 

 atomic weight would lead us. By means of 

 such side lights we may gradually acquire 

 some idea of the nature of the elements, 

 even if we are unable to get any clew to their 

 origin other than such as may be found in 

 Crookes's interesting speculations. 



The Camphor Tree. While camphor 

 was formerly produced in Sumatra, Borneo, 

 and other parts of the East Indies, all now 

 known to the trade comes from Japan and 

 Formosa. The camphor tree is a large ever- 

 green of symmetrical proportions, somewhat 

 resembling a linden. It bears a white flower 

 which ripens into a red berry. Some of the 



