126 



NATURE 



[June ii, 1908 



number of English and American mining engineers 

 who ^^■ilI appreciate a good dictionary of mining 

 teims, and certainly the author has spared no pains to 

 make his dictionary as complete as possible. He has 

 diligently studied the Spanish literature of mining 

 and metallurgy, and his long residence in Mexico and 

 in the United States of Colombia has enabled him 

 to include a very full list of the terms used in these 

 republics. Some Portuguese and Brazilian terms are 

 also added. 



It is curious to note that many terms have different 

 meanings in different districts of South America. 

 Thus, the well-known term Caliche, applied in Chile 

 and Peru to the impure native nitrate of soda which 

 is mined on a vast scale, denotes in the Uco district 

 of Peru a thin layer of clayey soil capping auriferous 

 veins, in Mexico felspar, and in Antioquia, Colombia, 

 a recently-discovered mineral vein. It is probable that 

 with the development of railway intercommunication 

 many of these terminological differences will dis- 

 appear, and that the most convenient terms will sur- 

 vive. In all cases the locality where a particular 

 term is in use is noted by the author, and the authority 

 is duly recorded. Small sketches, seventy-six in 

 number, are added when necessary to elucidate a de- 

 finition. The whole work has been compiled with 

 scrupulous accuracy, and deserves unstinted praise. It 

 is perhaps to be regretted that an English index 

 to the Spanish terms has not been included in the 

 scheme of tlie work. 



Innnanuel Kants Metapliysik dcr Sitten. Heraus- 



gegeben von Karl Vorliinder. Price 4.60 marks. 

 Kiichners Worterbiich der philosophischcn Grundbe- 



griffe. Neubearbeitung von Dr. Carl Michaelis. 



Price 8 marks. 

 B. de Spinoza's kursgefasste Abhandhing von Gott, 



dem Menschen tunl desscn Gluck. Ubersetzt von 



C. Schaarschmidt. 

 G. It'. F. Hegel's Phdnomenologie des Geistes. 



Jubiljiumsausgabe. Herausgegeben von Georg 



Lasson. Price 5 marks. (Leipzig : Durr'schen 



Buchhandlung, 1907.) 

 The first three of these volumes are new editions of 

 works that have been reprinted at various times in 

 the " Philosophische Bibliothek," a series which does 

 for the German student of philosophy what Ostwald's 

 well-known " Klassiker der exakten Wissenschaften " 

 do for the German student of the sciences. Hegel's 

 famous treatise has been added to the series in cele- 

 bration of the centenary of its original publication in 

 1S07. 



The books are admirably printed, and are provided 

 with excellent introductions, often by men of first- 

 rate authority. Many of them are, in addition, briefly 

 but helpfully annotated, while most are equipped with 

 a useful index. More conspicuously moderate in price 

 even than Ostwald's reprints, these wonderful 

 volumes, by their very existence, render almost un- 

 thinkable any English series comparable with them 

 in scope and importance. 



The Spectroscope : its Uses in General Analytical 

 Chemistry. By T. Thorne Baker. Pp. viii + 130. 

 (London : BaiUiere, Tindall and Cox, 1907.) 

 This volume contains a fair amount of information 

 useful to those wishing to purchase and set up spectro- 

 scopic apparatus for chemical research, but it seems 

 to us to be ill-assorted and indifl'crenllv arranged. 

 The author plunges straightway into the elementary 

 mathematics of the prism and plane and concave 

 gratings, and then describes the various parts of 

 spectroscopes ; yet on p. 78 it is thought necessary to 

 inform the reader that a 12-inch focus telescope lens 



XO. 2015, VOL. 78] 



will give a much shorter spectrum than an i8-inch 

 focus lens. There are, however, in the various dis- 

 courses on adjustments, refractive indices, resolving 

 power, the methods of producing radiation, sensitive 

 plates, &c., numerous hints which will be found 

 useful bv those who have only a general knowledge 

 of physics and wish to take up spectroscopy. It is for 

 such readers that the book is intended. The notes on 

 " series " and the Zecman effect would probably be 

 better left to the more advanced works on spectroscopy. 

 There are a few uncorrected misspellings and one or 

 two curious terms, which suggest that the author's 

 acquaintance with real, practical laboratory work has 

 been either too brief or too restricted. The astro- 

 phvsical side of the subject is not dealt with at all, 

 the idea being to restrict the book entirely to the 

 chemical side. W. E. R. 



Der Bedeittitng der Reinkullur. Eine Litcraturstiidic. 

 By Dr. Oswald Richter. Pp. viii+128. (Berlin: 

 Gebriider Borntraeger, 1907.) Price 4.40 marks. 

 This essay, with true German thoroughness, gives a 

 very complete, though necessarily brief, surve}" of the 

 various microscopic organisms that have been obtained 

 in pure cultivation. The organisms are dealt with 

 in groups (and not individually), partly according to 

 their biological position, partly according to the 

 changes they produce. The green and blue algae and 

 diatoms are first considered, then the bacteria — the 

 nitrifying forms, cellulose fennenters, sulphur bac- 

 teria, &c. — and lastly the yeasts and protozoa. In the 

 final portion of the book the subjects of pleomorphism 

 and systematic position of these organisms are dis- 

 cussed. The bibliography is a very full one, and it 

 is probable that this part of the compilation will be 

 most appreciated. R. T. H. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part 0/ Nature. 

 No notice is taken of anonymous communications.] 



The Coloration of Birds' Eggs. 



In Nature of May 14 Mr. R. L. Leslie asks if it is 

 known how and why birds' eggs become coloured, and 

 whether they illustrate Mendelian phenomena. 



Something is known as to the nature of the pigments 

 from which the colours are derived. The late Dr. H. C. 

 Sorby in 1S75 investigated their origin by means of the 

 spectrum analysis. He discovered seven substances in the 

 pigments accounting for every form of coloration. These 

 substances are oorhodeine (red), oocyan, banded ooycan 

 (blue), yellow ooxanthine, rufous ooxanthine (yellow and 

 reddish-j-ellow), a sixth substance of a brown tint, and 

 lichenoxanthine, found in many plants, lichens, and fungi, 

 and perhaps due to microscopic fungi. According to older 

 theories, the pigments were secretions from the blood and 

 bile, and in the case of the first three Sorby was disposed to 

 agree (c/. the origin of pigments in coloration of molluscan 

 shell). The ground-colour is laid on the shell just before 

 the extrusion of the egg, and in eggs not of a purely 

 uniform colour the markings are then superposed, being 

 originally rounded, but by movement of the bird they be- 

 come blurred and blotched. The intensity of coloration 

 varies with age up to a certain point. Eggs of 3'oung 

 birds are often unspotted. No doubt absence of markings 

 is due to deficiency of pigmentation. The last egg or 

 eggs of a second brood, in fact, often lack normal colora- 

 tion or markings. Age and health thus control coloration, 

 which is brilliant in a healthy but indistinct in an un- 

 healthy bird's egg. Whether albino birds lay eggs differ- 

 ing from those of birds typical in every way has not been 

 noticed apparently. 



Little is known definitely as to why eggs are coloured. 



